Makers of Electricity
BY
BROTHER POTAMIAN, F.S.C., D.SC., Lond.
PROFESSOR OF PHYSICS IN MANHATTAN COLLEGE, N. Y.
AND
JAMES J. WALSH, M. D., PH.D., LL.D.
DEAN AND PROFESSOR OF NERVOUS DISEASES AND OF THE HISTORY
OF MEDICINE AT FORDHAM UNIVERSITY SCHOOL OF MEDICINE;
PROFESSOR OF PHYSIOLOGICAL PSYCHOLOGY
AT THE CATHEDRAL COLLEGE, NEW YORK
[Illustration]
FORDHAM UNIVERSITY PRESS
NEW YORK
1909
Copyright, 1909,
FORDHAM UNIVERSITY PRESS,
New York.
PREFACE
This volume represents an effort in the direction of what may be called
the biographical history of electricity. The controlling idea in its
preparation was to provide brief yet reasonably complete sketches of the
lives of the great pioneer workers in electricity, the ground-breaking
investigators who went distinctly beyond the bounds of what was known
before their time, not merely to add a fringe of information to previous
knowledge, but to make it easy for succeeding generations to reach
conclusions in electrical science that would have been quite impossible
until their revealing work was done. The lives of these men are not only
interesting as scientific history, but especially as human documents,
showing the sort of men who are likely to make great advances in science
and, above all, demonstrating what the outlook of such original thinkers
was on all the great problems of the world around us.
In recent times, many people have come to accept the impression that
modern science leads to such an exclusive occupation with things
material, that scientists almost inevitably lose sight of the deeper
significance of the world of mystery in which humanity finds itself
placed on this planet. The lives of these great pioneers in electricity,
however, do not lend the slightest evidence in confirmation of any such
impression. They were all of them firm believers in the existence of
Providence, of a Creator, of man's responsibility for his acts to that
Creator, and of a hereafter of reward and punishment where the sanction
of responsibility shall be fulfilled. Besides, they were men
characterized by some of the best qualities in human nature. Their
fellows liked them for their unselfishness, for their readiness to help
others, for their devotedness to their work and to their duties as
teachers, citizens and patriots. Almost without exception, they were as
far above the average of mankind in their personal ethics as they were
in their intellectual qualities.
The lives of such men, who were inspiring forces in their day, are as
illuminating as they are instructive and encouraging. Perhaps never more
than now do we need such inspiration and illumination to lift life to a
higher plane of purpose and accomplishment, than that to which it is so
prone to sink when material interests attract almost exclusive
attention.
CONTENTS
Page
Peregrinus and Columbus 1
Norman and Gilbert 29
Franklin and some contemporaries 68
Galvani, discoverer of animal electricity 133
Volta, the founder of electrical science 162
Coulomb 188
Hans Christian Oersted 205
André Marie Ampère 232
Ohm, the founder of mathematical electricity 258
Faraday 299
Clerk Maxwell 334
Lord Kelvin 361
ILLUSTRATIONS
Page
The double pivoted needle of Petrus Peregrinus 19
First pivoted compass, Peregrinus, 1269 17
Magnetic Declination at New York 21
" " " San Francisco 21
" " in London, in 1580 and 1907 23
First dip-circle, invented by Norman in 1576 29
Norman's illustration of magnetic dip 31
Gilbert's orb of virtue, 1600 32
Behavior of compass-needle on a terrella or
spherical lodestone 44
Gilbert's "versorium" or electroscope 69
Gordon's electric chimes, 1745 75
Modern form of Leyden jar, with movable coatings 87
Three coated panes in series 89
" panes in parallel 89
" jars in parallel 90
" jars in cascade 90
Discharge by alternate contacts 94
Tassel of long threads or light strips of paper 101
Procopius Divisch (1696-1765) 108
The Divisch lightning conductor (1754) 111
Set of pointed rods 112
Galvani (portrait) opposite page 133
Volta " " " 162
Oersted " " " 205
Ampère " " " 232
Faraday " " " 299
Clerk Maxwell (portrait) opposite page 334
Lord Kelvin " " " 361
MAKERS OF ELECTRICITY.
CHAPTER I.
PEREGRINUS AND COLUMBUS.
The ancients laid down the laws of literary form in prose as well as in
verse, and bequeathed to posterity works which still serve as models of
excellence. Their poets and historians continue to be read for the sake
of the narrative and beauty of the style; their philosophers for breadth
and depth of thought; and their orators for judicious analysis and
impassioned eloquence.
In the exact sciences, too, the ancients were conspicuous leaders by
reason of the number and magnitude of the discoveries which they made.
You have only to think of Euclid and his "Elements," of Apollonius and
his Conics, of Eratosthenes and his determination of the earth's
circumference, of Archimedes and his mensuration of the sphere, and of
the inscription on Plato's Academy, _Let none ignorant of geometry enter
my door_, to realize the fondness of the Greek mind for abstract truth
and its suppleness and ingenuity in mathematical investigation.
But the sciences of observation did not advance with equal pace; nor was
this to be expected, as time is an essential element in experimentation
and in the collection of data, both of which are necessary for the
framing of theories in explanation of natural phenomena.
The slowness of advance is well seen in the development of the twin
subjects of electricity and magnetism. As to the lodestone, with which
we are concerned at present, the attractive property was the only one
known to ancient philosophy for a period of six hundred years, from the
time of Thales to the age of the Cæsars, when Lucretius wrote on the
nature of things in Latin verse.
Lucretius records the scant magnetic knowledge of his predecessors and
then proceeds to unfold a theory of his own to account for the phenomena
of the wonder-working stone. Book VI. of "De Natura Rerum" contains his
speculations anent the magnet, together with certain observations which
show that the poet was not only a thinker, but somewhat of an
experimenter as well. Thus he recognizes magnetic _repulsion_ when he
says: "It happens, too, at times that the substance of the iron recedes
from the stone as if accustomed to start back from it, and by turns to
follow it."
This recognition of the repelling property of the lodestone is
immediately followed by the description of an experiment which is
frequently referred to in works on magnetic philosophy. It reads: "Thus
have I seen raspings of iron, lying in brazen vessels, thrown into
agitation and start up when the magnet was moved beneath"; or
metrically,
And oft in brazen vessels may we mark
Ringlets of Samothrace, or fragments fine
Struck from the valid iron bounding high
When close below, the magnet points its powers.
This experiment, seen and recorded by Lucretius, is of special interest
to the student of magnetic history because of the use which is made of
iron filings and also because it has led certain writers to credit the
poet with a knowledge of what is known to-day by the various names of
magnetic figures, magnetic curves, magnetic spectrum. We do not,
however, share this view, because we see no adequate resemblance between
the positions assumed by the bristling particles of iron in the one
case, as described by the Roman poet, and the continuous symmetrical
curves of our laboratories in the other. If Lucretius noticed such
curves in his brazen vessels, he does not say so; nor does the meagre
description of magnetic phenomena given in Book VI. warrant us in
assuming that he did.
The use of iron filings to map out the entire field of force that
surrounds a magnet was unknown to classical antiquity; it was not known
to Peregrinus or Roger Bacon in the thirteenth century or even to
Gilbert in the sixteenth. The credit for reviving the use of filings and
employing them to show the direction of the resultant force at any point
in the neighborhood of a magnet, belongs to Cabeo, an Italian Jesuit,
who described and illustrated it in his "Philosophia Magnetica,"
published at Ferrara in the year 1629. On page 316 of that celebrated
work will be found a figure, the first of the kind, showing the position
taken by the filings when plentifully sifted over a lodestone: thick
tufts at the polar ends with curved lines in the other parts of the
field.
The Samothracian rings mentioned in the passage quoted above were light,
hollow rings of iron which, for the amusement of the crowd, the jugglers
of the times held suspended one from the other by the power of a
lodestone.
Writing of the lodestone, Lucretius says:
Its viewless, potent virtues men surprise,
Its strange effects, they view with wond'ring eyes,
When without aid of hinges, links or springs
A pendent chain we hold of steely rings.
Dropt from the stone--the stone the binding source--
Ring cleaves to ring and owns magnetic force;
Those held above, the ones below maintain;
Circle 'neath circle downward draws in vain
Whilst free in air disports the oscillating chain.
Though the Roman poet was acquainted with two of the leading properties
of the lodestone, viz., attraction and repulsion, there is nothing in
the lines quoted above or in any other lines of his great didactic poem
to indicate that he was aware of the remarkable difference which there
is between one end of a lodestone and the other. The polarity of the
magnet, as we term it, was unknown to him and remained unknown for a
period of 1200 years.
During that long period nothing of importance was added to the magnetic
lore of the world. True, a few fables were dug out of the tomes of
ancient writers which gained credence and popularity, partly by reason
of the fondness of the human mind for the marvelous, and partly also by
reason of the reputation of the authors who stood sponsors for them.
Pliny (23-79 A. D.) devotes several pages of his "Natural History" to
the nature and geographical distribution of various kinds of lodestones,
one of which was said to repel iron just as the normal lodestone
attracts it. Needless to say that the mineral kingdom does not hold such
a stone, although Pliny calls it _theamedes_ and says that it was found
in Ethiopia.
Pliny is responsible for another myth which found favor with subsequent
writers for a long time, when he says that a certain architect intended
to place a mass of magnetite in the vault of an Alexandrian temple for
the purpose of holding an iron statue of Queen Arsinoe suspended in
mid-air. Of like fabulous character is the oft-repeated story about
Mahomet, that an iron sarcophagus containing his remains was suspended
by means of the lodestone between the roof of the temple at Mecca and
the ground.
As a matter of fact, Mahomet died at Medina and was buried there in the
ordinary manner, so that the story as currently told of the suspension
of his coffin in the "Holy City" of Mecca, contains a twofold error, one
of place and the other of position. By a recent (1908) imperial irade of
the Sultan of Turkey, the tomb is lit up by electric light in a manner
that is considered worthy of the "Prophet of Islam."
Four centuries after Pliny, Claudian, the last of the Latin poets as he
is styled, wrote an idyl of fifty-seven lines on the magnet, which
contains nothing but poetic generalities. St. Ambrose (340-397) and
Palladius (368-430), writing on the Brahmans of India, tell how certain
magnetic mountains were said to draw iron nails from passing ships and
how wooden pegs were substituted for nails in vessels going to
Taprobane, the modern Ceylon. St. Augustine (354-430) records in his "De
Civitate Dei" the wonder which he felt in seeing scraps of iron
contained in a silver dish follow every movement of a lodestone held
underneath.
With time, the legendary literature of the magnet became abundant and in
some respects amusing. Thus we read of the "flesh" magnet endowed with
the extraordinary power of adhering to the skin and even of drawing the
heart out of a man; the "gold" magnet which would attract particles of
the precious metal from an admixture of sand; the "white" magnet used as
a philter; magnetic unguents of various kinds, one of which, when
smeared over a bald head, would make the hair grow; magnetic plasters
for the relief of headache; magnetic applications to ease toothaches and
dispel melancholy; magnetic nostrums to cure the dropsy, to quell
disputes and even reconcile husband and wife. No less fictitious was the
pernicious effect on the lodestone attributed in the early days of the
mariner's compass to onions and garlic; and yet, so deeply rooted was
the belief in this figment that sailors, while steering by the compass,
were forbidden the use of these vegetables lest by their breath they
might intoxicate the "index of the pole" and turn it away from its true
pointing. More reasonable than this prohibition was the maritime
legislation of certain northern countries for the protection of the
lodestone on shipboard. According to this penal code, a sailor found
guilty of tampering with the lodestone used for stroking the needles,
was to have the guilty hand held to a mast of the ship by a dagger
thrust through it until, by tearing the flesh away, he wrenched himself
free.
It was only at the time of the Crusades that people in Europe began to
recognize the _directive_ property of the magnet, in virtue of which a
freely suspended compass-needle takes up a definite position relatively
to the north-and-south line, property which is serviceable to the
traveler on land and supremely useful to the navigator on sea.
It is commonly said that the compass was introduced into Europe by the
returning Crusaders, who heard of it from their Mussulman foes. These,
in turn, derived their knowledge from the Chinese, who are credited with
its use on sea as far back as the third century of our era.[1]
Among the earliest references to the sailing compass is that of the
trouvère Guyot de Provins,[2] who wrote, about the year 1208, a
satirical poem of three thousand lines, in which the following passage
occurs:
The mariners employ an art which cannot deceive.
An ugly stone and brown,
To which iron joins itself willingly
They have; after applying a needle to it,
They lay the latter on a straw
And put it simply in the water
Where the straw makes it float.
Then the point turns direct.
To the star with such certainty
That no man will ever doubt it,
Nor will it ever go wrong.
When the sea is dark and hazy,
That one sees neither star nor moon,
Then they put a light by the needle
And have no fear of losing their way.
The point turns towards the star;
And the mariners are taught
To follow the right way.
It is an art which cannot fail.
The author was a caustic and fearless critic, who lashed with equal
freedom the clergy and laity, nobles and princes, and even the reigning
pontiff himself, all of whom should be for their subjects, according to
the satirist, what the pole-star is for mariners--a beacon to guide them
over the stormy sea of life.
Guyot traveled extensively in his early years, but later in life retired
from a world which he despised, and ended his days in the peaceful
seclusion of the Benedictine Abbey of Cluny.
An interesting reference, of a similar nature to that of the minstrel
Guyot, is found in the Spanish code of laws known as Las Siete Partidas
of Alfonso el Sabio, begun in 1250 and completed in 1257. It says:
"And even as mariners guide themselves in the dark night by the needle,
which is their connecting medium between the lodestone and the star, and
thus shows them where they go alike in bad seasons as in good; so those
who are to give counsel to the king ought always to guide themselves by
justice, which is the connecting medium between God and the world, at
all times to give their guerdon to the good and their punishment to the
Wicked, to each according to his deserts."[5]
It will be necessary to give a few more extracts from writers of the
first half of the thirteenth century in order to show how little was
known about the magnet and how crude were the early appliances used in
navigation when Peregrinus appeared on the scene.
Cardinal Jacques de Vitry, who lived in the East for some years, wrote
his "History of the Orient" between the years 1215 and 1220, in which he
says:
"An iron needle after touching the lodestone, turns towards the north
star, so that such a needle is necessary for those who navigate the
seas."
This passage of the celebrated Cardinal seems to indicate that even then
the compass was widely known and commonly used in navigation.
Neckam (1157-1217), the Augustinian Abbot of Cirencester, wrote in his
"Utensilibus":
"Among the stores of a ship, there must be a needle _mounted on a dart_
which will oscillate and turn until the point looks to the north; the
sailors will thus know how to direct their course when the pole-star is
concealed through the troubled state of the atmosphere."
This passage is of historical value, as it contains what is probably the
earliest known reference to a mounted or pivoted compass. Prior to the
introduction of this mode of suspension, the needle was floated on a
straw, in a reed, on a piece of cork or a strip of wood, all of which
modes of flotation, when taken in conjunction with the unsteadiness of
the vessel in troubled waters, must have made observation difficult and
unsatisfactory.
Brunetto Latini (1230-1294) makes a passing reference to the new
magnetic knowledge in his "Livres dou Tresor," which he wrote in 1260,
during his exile in Paris.
"The sailors navigate the seas," he says, "guided by the two stars
called tramontanes; and each of the two parts of the lodestone directs
the end of the needle that has touched it to the particular star to
which that part of the stone itself turns."
Though a statesman, orator and philosopher of ability, the preceptor of
Dante in Florence and guest of Friar Bacon in Oxford, Brunetto has not
got the philosophy of the needle quite right in this passage; for the
part that has been touched by the north end of a lodestone will acquire
south polarity and will not, therefore, turn towards the same
"tramontane" as the end of the stone by which it was touched.
Dante himself admitted the occult influence on the compass-needle that
emanates from the pole-star when he wrote:
"Out of the heart of one of the new lights
There came a voice that, needle to the star,
Made me appear in turning thitherward.
_Paradise_, XII., 28-30.
The next writer on the compass is Raymond Lully (1236-1315), who was
noted for his versatility, voluminous writings and extensive travels as
well as for the zeal which he displayed in converting the African
Moors. Lully writes in his "De Contemplatione": "As the needle after
touching the lodestone, turns to the north, so the mariners' needle
directs them over the sea."
This brings us to the last of our ante-Peregrinian writers who make
definite allusions to the use of the compass for navigation purposes,
viz., Roger Bacon, one of the glories of the thirteenth century as he
would be of the twentieth. It was at the request of his patron, Pope
Clement IV., that Bacon wrote his "Opus Majus," a work in which he
treats of all the sciences and in which he advocates the experimental
method as the right one for the study of natural phenomena and the only
one that will serve to extend the boundaries of human knowledge. In a
section on the magnet, a clear distinction is drawn between the physical
properties of the two ends of a lodestone; for "iron which has been
touched by a lodestone," he says, "follows the end by which it has been
touched and turns away from the other." Besides being a recognition of
magnetic polarity, this is equivalent to saying that unlike poles
attract while like poles repel each other. Bacon further remarks, by way
of corroboration, that if a strip of iron be floated in a basin, the end
that was touched by the lodestone will follow the stone, while the other
end will flee from it as a lamb from the wolf. There is, however, an
earlier recognition known of the polarity of the lodestone; for Abbot
Neckam, fifty years before, called attention to the dual nature of the
physical action of the lodestone, attracting in one part (say) by
sympathy and repelling at the other by antipathy. It was the common
belief in Bacon's time and for centuries after, that the compass-needle
was directed by the pole-star, often called the sailor's star; but Bacon
himself did not think so, preferring to believe with Peregrinus, that it
was controlled not by any one star or by any one constellation, but by
the entire celestial sphere. Other contemporaries of his sought the
cause of the directive property not in the heavens at all, but in the
earth itself, attributing it to hypothetical mines of iron which,
naturally enough, they located in regions situated near the pole.
Peregrinus records this opinion, which he criticises and rejects, saying
in Chapter X. that persons who hold such a doctrine "are ignorant of the
fact that in many different parts of the globe the lodestone is found;
from which it would follow that the needle should turn in different
directions, according to the locality, which is contrary to experience."
A little further on he gives his own view, saying: "It is evident from
the foregoing chapters that we must conclude that not only from the
north pole (of the world), but also from the south pole rather than from
the veins of mines, virtue flows into the poles of the lodestone."
Observations had to accumulate and much experimentation had to be done
before it was finally established that the cause of the directive
property of the magnet is not to be sought in the remote star depths at
all, but in the earth itself, the whole terrestrial globe acting as a
colossal magnet, partly in virtue of magnetic ore lying near the surface
and partly also in virtue of electrical currents, due to solar heat,
circulating in the crust of the earth.
Of the early years of Pierre le Pélérin (Petrus Peregrinus), nothing is
known save that he was born of wealthy parents in Maricourt, a village
of Picardy in Northern France. From his academic title of Magister, we
infer that he received the best instruction available at the time,
probably in the University of Paris, which was then in the height of its
fame. His reputation for mathematical learning and mechanical skill
crossed the Channel and reached Friar Bacon in the University of Oxford.
In his "Opus Tertium," the Franciscan Friar records the esteem in which
he held his Picard friend, saying: "I know of only one person who
deserves praise for his work in experimental philosophy, because he does
not care for the discourses of men or their wordy warfare, but quietly
and diligently pursues the works of wisdom. Therefore it is that what
others grope after blindly, as bats in the evening twilight, this man
contemplates in all their brilliancy because he is master of
experiment."
Continuing the appraisal of his Gallic friend's achievements, he says:
"He knows all natural sciences, whether pertaining to medicine and
alchemy or to matters celestial and terrestrial. He has worked
diligently in the smelting of ores and also in the working of minerals;
he is thoroughly acquainted with all sorts of arms and implements used
in military service and in hunting, besides which he is skilled in
agriculture and also in the measurement of lands. It is impossible to
write a useful or correct treatise on experimental philosophy without
mentioning this man's name. Moreover, he pursues knowledge for its own
sake; for if he wished to obtain royal favor, he could easily find
sovereigns to honor and enrich him."
This is at once a beautiful tribute to the work and character of
Peregrinus and an emphatic recognition of the paramount importance of
laboratory methods for the advancement of learning. It is evident from
such testimony, coming as it does from an eminent member of the
brotherhood of science, that the world had not to wait for the advent of
Chancellor Bacon or for the publication of his _Novum Organum_ in 1620,
to learn how to undertake and carry out a scientific research to a
reliable issue. Call the method what you will, inductive, deductive or
both, the method advocated by the Franciscan friar of the thirteenth
century was the one followed at all times from Archimedes to Peregrinus
and from Peregrinus to Gilbert, none of whom knew anything of Lord
Bacon's pompous phrases and lofty commendation of the inductive method
of inquiry for the advancement of physical knowledge. Be it said in
passing, that Bacon, eminent as he undoubtedly was in the realm of the
higher philosophy, was, nevertheless, neither a mathematician nor a man
of science; he never put to a practical test the rules which he laid
down with such certitude and expectancy for the guidance of physical
inquiry. Moreover, there is not a single discovery in science made
during the three centuries that have elapsed since the promulgation of
the Baconian doctrine that can be ascribed to it; it has been steadily
ignored by men renowned in the world for their scientific achievements
and has been absolutely barren of results.
Peregrinus, on the other hand, does not stop to enumerate opinions, he
does not even quote Aristotle; but he experiments, observes, reasons and
draws conclusions which he puts to the further test of experiment before
finally accepting them. Then and then only does he rise from the order
of the physicist to that of the philosopher, from correlating facts and
phenomena to the discovery of the laws which govern them and the causes
that produce them. Furthermore, he was in no hurry to let the world know
that he was grinding lodestones one day and pivoting compass-needles the
next; what he cared for supremely was to discover facts, new phenomena,
new methods. Peregrinus was not an essayist, nor was he a man of mere
book-learning. He was a clear-headed thinker, a close and resourceful
worker, a man who preferred facts to phrases and observation to
speculation.
At one period of his life, Master Peter applied his ingenuity to the
solution of a problem in practical optics, involving the construction of
a burning-mirror of large dimensions somewhat after the manner of
Archimedes; but though he spent three years on the enterprise and a
correspondingly large sum of money, we are not told by Friar Bacon, who
mentions the fact, what measure of success was achieved. Bacon, however,
avails himself of the occasion to insinuate a possible cause of failure,
for he says that nothing is difficult of accomplishment to his friend
_unless it be for want of means_.
Centuries later, the French naturalist Buffon took up the same optical
problem, with a view to showing that the feat attributed to Archimedes
during the siege of Syracuse by the Romans was not impossible of
accomplishment. For this purpose, he used 168 small mirrors in the
construction of a large concave reflector, with which he ignited wood at
a distance of 150 feet and succeeded in melting lead at a distance of
140 feet. As this was done in the winter time in Paris, it was concluded
that it would have been quite possible to set a Roman trireme on fire
from a safe distance by the concentrated energy of a Sicilian sun.
If Peregrinus was alert in mind, he appears to have been very active in
body. Prompted, no doubt, by the higher motives of Christian faith and
perhaps a little, too, by his fondness for travel and adventure, he took
the cross in early life and joined one of the crusading expeditions of
the time. That he went to the land of the paynim, we have no direct
evidence; but we infer the fact from the title of Peregrinus or Pilgrim,
by which he is known, his full name being Pierre le Pélérin de
Maricourt, or, in the Latinized form, Petrus Peregrinus de Maricourt.
In 1269, we find him engaged in a military expedition undertaken by
Charles Duke of Anjou, for the purpose of bringing back to his
allegiance as King of the Two Sicilies the revolted city of Lucera in
Southern Italy. He served in what might be called the engineering corps
of the army, and was engaged in fortifying the camp and constructing
engines of defense and attack. Unlike his companions in arms, Peregrinus
does not allow himself to be wholly absorbed with military duties, nor
does he waste his leisure hours in frivolous amusements; his mind is on
higher things; he is engrossed with a problem in practical mechanics
which required him to devise a piece of mechanism that would keep an
armillary sphere in motion for a time.
In outlining the necessary mechanism, as he conceived it, he was
gradually led to consider the general and more fascinating problem of
perpetual motion itself, with the result that he waxed somewhat
enthusiastic when he thought that he saw the possibility of constructing
an ever-turning wheel in which the motive power would be magnetic
attraction, the attraction of a lodestone for a number of iron teeth
arranged at equal distances on the periphery of a wheel. The device
looked well on paper, beyond which stage it was not carried, perhaps for
want of leisure, or more probably for want of the necessary material and
tools. Had Peregrinus been able to test his theoretical views on the
_magnetic motor_ by actual experiment, the delusive character of
perpetual motion would have been recognized at an early epoch in the
world's history, and much time and money spared for more profitable
investment.
This very wheel, which was designed in the trenches before Lucera in
1269, was probably the cause of the withering rebuke which Justin Huntly
McCarthy administers in his "History of the French Revolution," Vol. I.,
p. 256, where he says: "In the long record of rascaldom from
_Peregrinus_ to Bamfylde Moore Carew, no single rascal stands forward
with such magnificent effrontery, such majestic impudence, such
astonishing success as Cagliostro." To say the least, this is a very
serious slip of the pen on the part of the Irish historian of the French
Revolution, in which a scientific pioneer of the first rank and a
patriot of exalted type is mistaken for a charlatan of the deepest dye.
Although Peregrinus puts the burden of constructing his wheel on others,
he does not appear to have considered it a vain conceit; for, in the
beginning of the last chapter of the "Epistola" he says: "In this
chapter, I will make known to you the construction of a wheel which, in
a remarkable manner, moves continuously." He is writing from Southern
Italy to his friend Siger (Syger, Sygerus), at home in Picardy; and that
this friend may the better comprehend the mechanism of the wheel, he
proceeds to describe in a systematic manner the various properties of
the lodestone, all of which he had investigated and many of which he had
discovered. The "Epistola" of Peregrinus is, therefore, the first
treatise on the magnet ever written; it stands as the first great
landmark in magnetic philosophy.
The work is divided into two parts--the first contains ten chapters and
the latter three. "At your request," he says to his friend, "I will
make known to you in an unpolished narrative the undoubted though hidden
virtue of the lodestone, concerning which philosophers, up to the
present time, give us no information. Out of affection for you, I will
write in simple style about things entirely unknown to the ordinary
individual."
[Illustration: FIG. 1 The double pivoted needle of Petrus Peregrinus, A.
D., 1269]
After this declaration as to the original character of his work
Peregrinus proceeds: "You must know that whoever wishes to experiment
should be acquainted with the nature of things; he must also be skilled
in manipulation, in order that by means of this stone, he may produce
those marvelous results."
The titles of the chapters will give an idea of the comprehensive
character of the magnetic work accomplished by the author and, at the
same time, will serve to show how much was known about the lodestone in
the thirteenth century.
PART I.
Chap. I. Purpose of this work.
II. Qualifications of the experimenter.
III. Characteristics of a good lodestone.
IV. How to distinguish the poles of a lodestone.
V. How to tell which pole is north and which south.
VI. How one lodestone attracts another.
VII. How iron touched by a lodestone turns towards the
poles of the world.
VIII. How a lodestone attracts iron.
IX. Why the north pole of one lodestone attracts the south
pole of another, and _vice versa_.
X. An inquiry into the natural virtue of the lodestone.
PART II.
Chap. I. Construction of an instrument for measuring the azimuth
of the sun, the moon or any star when in
the horizon.
II. Construction of a better instrument for the same purpose.
III. The art of making a wheel of perpetual motion.
An attentive reading of the thirteen chapters of this treatise of 3,500
words will show that:
(1) Peregrinus assigns a definite position to what he calls the _poles_
of a lodestone and gives practical directions for determining which is
north and which south.
(2) He establishes the two fundamental laws of magnetism, that like
poles repel and unlike poles attract each other.
(3) He demonstrates by experiment that every fragment of a lodestone is
a complete magnet, and shows how the fragments should be put together in
order to reproduce the polarity of the unbroken stone.
(4) He shows how a pole of a lodestone may neutralize a weaker one of
the same name and even reverse its polarity.
(5) He pivots a magnetized needle and surrounds it with a circle divided
into 360 degrees.
This brief summary shows the great advance made by the author on what
was known about the lodestone before his time. Most of the salient facts
in magnetism are clearly described and some of their applications
pointed out. So thorough and complete was this apprehension and
explanation of magnetic phenomena that nothing of importance was added
to it for the next three hundred years.
[Illustration: FIG. 2 First pivoted compass, Peregrinus, 1269]
In the compass which Peregrinus devised for use in navigation, a light
magnetic needle was thrust through a slender vertical axis made of wood,
which axis also carried a pointer of brass or silver at right angles to
the needle. According to the belief of the time, the magnetic needle
gave the north and south points of the horizon, while the brass pointer
determined the east and west points. This compass, double pivoted be it
noticed, was provided with a graduated circle and a movable arm, having
a pair of upright pins at its extremities, which movable arm enabled the
navigator to determine the magnetic bearing of the sun, moon or any star
at the time of rising or setting. "By means of this instrument," the
author says in Chap. II., "you can direct your course towards cities and
islands and any other place wherever you may wish to go, by land or by
sea, provided you know the latitude and longitude of the place which you
want to reach."
The invention of the compass has been attributed to one Flavio Gioja, a
seafaring man of Amalfi, a flourishing maritime town in Southern Italy.
If we admit that Gioja was a real and not a fictitious person, we
cannot, however, admit the claim which is made by his countrymen, when
they say that he gave to the mariner the use of the compass in the year
1302; for we have seen that Peregrinus distinctly states that his
compass, described in 1269, could be relied upon for guidance by the
traveler on land as well as by the voyager on sea.
To Gioja may belong the merit of having simplified and improved the
compass. It is likely that he suspended the needle on one pivot instead
of the two used by Peregrinus, and that he added the compass-card with
its thirty-two divisions, attaching it to the needle itself, thereby
adding materially to the practical character of the compass as a
nautical instrument.
On the other hand, a claim has been made for Peregrinus which cannot be
admitted. It was put forward by his itinerant countryman Thévenot, in
the seventeenth century, to the effect that the author of the "Epistola"
was acquainted with magnetic declination, in virtue of which a freely
suspended magnet does not point north and south, but cuts the
geographical meridian at a definite angle.
Writing in 1681, Thévenot says in his "Recueil de Voyages" that: "It was
a matter of general belief down to the present day, that the declination
of the magnetic needle was first observed sometime in the beginning of
the last (16th) century. I have found, however, that there was a
declination of five degrees in the year 1269, having found it recorded
in a manuscript with the title "Epistola Petri Adsigerii," etc.
The title of the manuscript seen by Thévenot is not, however, as he
gives it above, but "Epistola Petri ad Sygerium," etc., which is quite a
different reading.
There are twenty-eight manuscript copies of the "Epistola" known to
exist; and only one of them, that of the University of Leyden, contains
the passage alluded to by Thévenot. This manuscript was the object of
careful study and critical examination by Wenckebach (1865) and other
competent scholars, who pronounced it a spurious addition made some time
in the early part of the 16th century.[4]
In the time of Peregrinus, it is probable that the declination did not
exceed three degrees in Paris or on the shores of the Mediterranean, a
quantity so small that it would have been difficult of detection; and,
if detected, would have been attributed either to errors in the
construction of the instrument used or to inaccuracy on the part of the
observer. This is what happened to Columbus when, on his return to
Spain, having reported the many and definite observations on the
variation of the compass which he had made on his outward voyage, he was
told by the learned ones of the day that _he_ was in error and not the
needle, because the latter was everywhere true to the pole.
[Illustration: FIG. 3]
This oft-stated and widely-believed fidelity of the needle to the pole
is not, however, founded on fact; it is the exception, the rare
exception, not the rule, despite the couplet of the poet:
Th' obedient steel with living instinct moves
And veers for ever to the pole it loves;
or this other,
So turns the faithful needle to the pole,
Though mountains rise between and oceans roll.
That the magnet does not turn to the pole of the world is common
knowledge to-day, when the High School tyro will tell you that in New
York it points 9° _west_ of north, while in San Francisco it points 15°
_east_ of north. If he happens to be well up, he may refer to the
position of the agonic line on the globe along which the needle stands
true to the pole, while all places to the east of that line in our
hemisphere have westerly declination and those to the west have easterly
declination. Indeed, magnetic charts show places where the needle points
east and west instead of north and south, and others where the
north-seeking end points directly south. Such varying and conflicting
behavior of the compass-needle serves to show the irregular manner in
which the earth's magnetism is distributed and also the intensity of
distributing forces which exist at certain places.
It is one of the gems in the crown of Columbus, that he observed,
measured and recorded this strange behavior of the magnetic needle in
his narrative of the voyage. True, he did not notice it until he was far
out on the trackless ocean. A week had elapsed since he left the lordly
Teneriffe, and a few days since the mountainous outline of Gomera had
disappeared from sight. The memorable night was that of September 13th,
1492. There was no mistaking it; the needle of the _Santa Maria_ pointed
a little west of north instead of due north. Some days later, on
September 17th, the pilots, having taken the sun's amplitude, reported
that the variation had reached a whole point of the compass, the
alarming amount of 11 degrees.
The surprise and anxiety which Columbus manifested on those occasions
may be taken as indications that the phenomenon was new to him. As a
matter of fact, however, his needles were not true even at the outset
of the voyage from the port of Palos, where, though no one was aware of
it, they pointed about 3° _east_ of north. This angle diminished from
day to day as the Admiral kept the prow of his caravel directed to the
west, until it vanished altogether, after which the needles veered to
the _west_, and kept moving westward for a time as the flag-ship
proceeded on her voyage.
[Illustration: FIG. 4 Magnetic Declination in London in 1580 and in
1907]
Columbus thus determined a place on the Atlantic in which the magnetic
meridian coincided with the geographical and in which the needle stood
true to the pole. Six years later, in 1498, Sebastian Cabot found
another place on the same ocean, a little further north, in which the
compass lay exactly in the north-and-south line. These two observations,
one by Columbus and the other by Cabot, sufficed to determine the
position of the _agonic line_, or line of no variation, for that
locality and epoch.
The _Columbian_ line acquired at once considerable importance, in the
geographical and the political world, because of the proposal that was
made to discard the Island of Ferro and take it for the prime meridian
from which longitude would be reckoned east and west, and also because
it was selected by Pope Alexander VI. to serve as a line of reference in
settling the rival claims of the kingdoms of Portugal and Castile with
regard to their respective discoveries. It was decided that all recently
discovered lands lying to the east of that line should belong to
Portugal; and those to the west, to Castile.
The line of no variation, like all other isomagnetic lines, has shifted
its position with time, so that it runs to-day considerably to the west
of the place assigned to it by Columbus in 1492 and by the Papal Bull of
the following year.
Columbus did not speak of the disquieting observation which he made on
the night of the 13th of September; he thought of it, and wondered
greatly what might be the cause of such an unexpected and untoward
phenomenon. His silence on the matter did not avail, for the keen-eyed
sailors noticed the westerly deflection of the needle when, after a few
days, it became quite apparent. They grew alarmed, believing that the
laws of nature were changing as they advanced farther and farther into
the unknown. It was a trying moment for the Admiral, but his ingenuity
and tactfulness rose to the occasion. He told his seamen that the needle
did not point to the _cynosure_ or last star in the tail of the Little
Bear, as commonly supposed, but to a fixed point in the celestial sphere
at which there was no star, adding that the "cynosure" itself, the
Polaris of our days, was not stationary, but had a rotational movement
of its own like all other heavenly bodies.
We do not know what Columbus thought of his explanation, born of the
stress of the moment, but the esteem in which he was held by pilots and
sailors alike for his knowledge of astronomy and cosmography led them to
accept it. Their fears were allayed, a mutiny was averted and a
successful termination to their voyage rendered possible.
Captains of ocean-liners would give to-day a different answer to a
passenger who might consult them about the splinter of steel which
serves to guide their fleet vessels in darkest nights, through howling
tempests and over billowy seas. The mysterious influence that controls
it, they would say, comes neither from Polaris nor the pole of the
world, nor from the heavens above, but from the earth beneath.
Such an explanation was not thought of until it was clearly shown a
hundred years later that this globe of ours acts like a colossal
lodestone, controlling every magnet in our laboratories and
observatories, and every needle on board the merchantmen and
fighting-monsters that plough our seas and oceans.
Without any intuition of modern theory, Columbus made two discoveries in
terrestrial magnetism, as we have seen, each of fundamental importance,
whether considered from the view-point of pure science or that of
practical navigation, viz., (a) that the needle is not true to the pole
and (b) that the angular displacement of the needle from true
orientation, the _variation of the compass_, as it is called in nautical
parlance, differs with the place of the observer. These two discoveries
as well as the location of a place of no variation on the Atlantic Ocean
entitle Columbus to a prominent place among the founders of the
_science_ of terrestrial magnetism.
Later observers discovered that even for a given place this element of
magnetic declination has not a constant value, but undergoes changes
which complete their cycle, some in a day, others in a year, and others
again in centuries. The last or _secular_ change in the direction of the
magnetic needle was discovered by Gellibrand, of London, in 1634
(published in 1635); the _annual_, by Cassini, at Paris, 1782-1791; and
the _diurnal_, by Graham, of London, in 1722.
The first observation of magnetic declination on _land_ appears to have
been made about the year 1510 by George Hartmann (1489-1564), Vicar of
the Church of St. Sebald in Nuremberg, who found it to be 6° east in
Rome, where he was living at the time. Hartmann's observation of the
declination in Rome and also in Nuremberg, where the needle pointed 10°
east of north, will be found in a letter which he wrote in 1544 to Duke
Albert of Prussia and which remained unpublished until the year 1831.
Returning to the treatise of Peregrinus on the magnet, it should be said
that for several centuries the twenty-eight manuscript copies lay
undisturbed on the dusty shelves of city and university libraries. In
1562, four years after the appearance of the first printed edition
(Augsburg, 1558), Taisnier, a Belgian writer on magnetics, who is also
described as poet-laureate and Doctor "utriusque juris," was among the
earliest to discover the "Epistola," from which he copied extensively in
his little quarto on the magnet and its effects, thus showing that there
were literary pirates in those days. It was also well known to Gilbert,
to Cabeo and Kircher; but despite the references of these writers, the
"Epistola" remained practically unknown until Cavallo, of London, called
attention to the Leyden manuscript in the third edition of his "Treatise
on Magnetism,"[3] 1800, by giving part of the text and accompanying it
with a translation.
Later, in 1838, Libri, historian of the mathematical sciences in Italy,
gave excerpts from the Paris codex with translation; but the scholar who
contributed most of all to make the work of Peregrinus known is the
Italian Barnabite, Timoteo Bertelli, who published in 1868 a critical
study of the various manuscripts of the letter, principally those which
he found in Rome and in Florence, adding copious notes of historic,
bibliographic and scientific value. Father Bertelli was Professor of
Physics in the Collegio della Quercia, in Florence, where he took an
active interest in Italian seismology besides carrying on investigations
in meteorology, telegraphy and electricity. Born in Bologna in 1826, he
died in Florence in March, 1905.
The following list of manuscript copies of the "Epistola" is taken from
a scholarly paper by Professor Silvanus P. Thompson, of London, which
appeared in the "Proceedings of the British Academy" for 1906:--
The Bodleian Library seven
Vatican four
British Museum one
Bibliothèque Nationale, Paris two
Biblioteca Riccardiana, Florence one
Trinity College, Dublin one
Gonville and Caius, Cambridge one
The University of Leyden one
Geneva one
Turin one
Erfurt three
Vienna three
S. P. Thompson two
The first printed edition of the "Epistola" was prepared for the press
in 1558 by Achilles Gasser, a man well versed in the science and
philosophy of his day; another edition, which will probably be
considered the _textus receptus_, is that which was prepared and
published by Bertelli in 1868.
No complete translation in any language of this historical work on
magnetism was made until 1902, when Prof. Silvanus P. Thompson, of
London, published his "Epistle of Peter Peregrinus of Maricourt to
Sygerus of Foncaucourt, soldier, concerning the Magnet." Unfortunately,
this translation was printed for private circulation and limited to 250
copies. Two years later, 1904, Brother Arnold, F. S. C., presented a
memoir on Peregrinus, including a translation of the "Epistola," for the
M. Sc. degree of Manhattan College, New York City, which translation was
published some months later by the McGraw Publishing Company, New York.
These are the only complete translations of the "Letter" of Peregrinus
on the Magnet which have yet appeared.
BROTHER POTAMIAN.
FOOTNOTES:
[1] See Klaproth, "Lettre à M. le Baron A. de Humbolt sur
l'Invention de la Boussole." 1834; also Encyc. Brit., article
_Compass_.
[2] Provins, town 57 miles southeast of Paris.
[3] Southey, "Omniana," Vol. I., p. 213, ed. 1812.
[4] Annali di Matematica pura ed applicata. Rome, 1865.
[5] Also in _Rees_ Encyclopedia, article _Compass_.
CHAPTER II.
NORMAN AND GILBERT.
We have seen that in the thirteenth century the directive property of
the lodestone was recognized by Peregrinus and used by him in his
pivoted compass; and that in the fifteenth, Columbus discovered magnetic
declination on sea as well as its variation with place.
The next cardinal fact in terrestrial magnetism, magnetic dip, was
discovered in 1576 by Robert Norman, a compass-maker of Limehouse,
London. Norman possessed many of the fine qualities of mind, hand and
disposition that are indispensable in the make-up of the original
investigator. In pivoting his compass-needles, he soon noticed that,
however carefully they were balanced before being magnetized, they did
not remain horizontal after magnetization, the north-seeking end always
going down through a small angle. He next had the happy idea of swinging
a needle on a horizontal axis, so that it might be free to move up and
down in a vertical plane, with the result that the north-seeking end
again went down through a constant but much greater angle.
[Illustration: FIG. 5 The first dip-circle, invented by Norman in 1576]
Like declination, the first discovered of the three magnetic elements,
the dip was found to vary with place on the earth's surface, being 0° at
the magnetic equator and 90° at either pole. It was with a Norman
dip-circle, greatly improved, that Ross in 1831 found the north magnetic
pole of the earth to be in Boothia Felix in latitude 70° 5'.3 N., and
longitude 96° 45'.8 W.; and it was with a similar instrument that
Amundsen recently studied the magnetic conditions of that Arctic region,
the exact location of the pole itself being finally determined by an
earth-inductor or spinning coil of the latest make. Though the results
of his observations have not yet been made public, it is generally known
that they indicate a spot for the magnetic pole close to that found by
Sir James Ross. It is not expected, however, that the location of the
pole by the Norwegian Commander shall exactly coincide with that of the
English Captain, because the magnetic pole is believed to have nomadic
tendencies of its own like our geographical pole, only much more
pronounced in magnitude. After moving westward for some time at the rate
of a mile per year, it retraced its steps and is now back again in the
vicinity of its starting place.
Besides his dip-circle, Norman also devised a simple and very apt
illustration of magnetic inclination. Thrusting a steel needle through a
round piece of cork, he pared the latter down until the system,
consisting of the needle and the cork, sank to a certain depth in a
glass vessel containing water, and there took up a horizontal position.
The needle was next removed from the water and magnetized with great
care, so as not to disturb its position in the cork. When placed again
in the water, the needle sank to its former depth and settled down at an
angle of 71° to the horizon.
The same illustration shows another experiment which Norman made in
order to determine whether the earth exerts a force of translation on a
magnet, in virtue of which the magnet would tend to move bodily toward
the pole. For this purpose, he floated a magnetized piece of steel wire
on the surface of the water and noticed that, wherever placed, it merely
swung round into the magnetic meridian without showing any tendency to
move northward or southward toward the rim of the vessel. Hartmann, who
observed the declination of the needle on land as stated on p. 26,
appears also to have been the first to notice magnetic inclination.
Having balanced a steel needle with great precision, he found that,
after magnetization, it did not remain horizontal, the north-seeking end
invariably dipping through an angle of 9°. The smallness of the angle in
this experiment was due to the fact that the needle used by the
Nuremberg Vicar could move only in a horizontal plane, whereas Norman's
was free to move in a vertical circle. Had Hartmann used such a device,
he would have obtained more than 60° for the dip instead of the 9° which
he records.
[Illustration: FIG. 6 Norman's illustration of magnetic dip]
As already remarked, the letter in which Hartmann consigns these capital
observations was written in 1544, but was not published until the third
decade of the nineteenth century, so that Norman has clearly the full
merit of independent discovery.
In the directions which Norman gives for making observations of dip, he
states explicitly that the instrument must be adjusted "duley according
to the variation of the place," which means that the plane of the circle
must be turned into what was called after his time "the magnetic
meridian."
The discovery of magnetic dip led Norman to discard the view generally
held in his time, which placed the controlling influence of the
compass-needle in far-off celestial space; for he says that the _poynt
respective_ which the magnet indicates, but to which it is not bodily
drawn, is not in the heavens above, but in the earth itself. His words
are: "And by the declining of the needle is also proved that the poynt
respective is rather in the earth than in the heavens, as some have
imagined; and the greatest reason why they so thought, as I judge, was
because they were never acquainted with this declining in the needle."
Here we have a radical departure from the scientific creed of the time,
a notable advance in scientific theory, an entirely new philosophy
founded by Norman, the compass-maker, and greatly developed twenty-four
years later by his fellow-citizen, Gilbert, the physician.
[Illustration: FIG. 7 Gilbert's _orb of virtue_, 1600]
Norman made another remark of great importance in the new philosophy,
the justness of which was appreciated by Gilbert, his contemporary, but
more so by Faraday and Clerk Maxwell, two centuries later. It refers to
the space surrounding a magnet, natural or artificial, which cubical
space Gilbert, following Norman, called an _orb of virtue_. That the
influence or "effluvium" of the magnet extends throughout the entire
space may readily be seen by carrying a compass-needle round a magnet
from point to point, far away as well as close by. The phrase "orb of
virtue," or sphere of magnetic influence, appears to describe the actual
magnetic condition of the space in question more pertinently than our
modern equivalent of "magnetic field."
The words of Norman are very remarkable: "I am of opinion that if this
vertue could by anie means be made visible to the eie of man, it would
be found in a sphericall forme, extending round about the stone in great
compasse and the dead bodie of the stone in the middle thereof." The
lines which immediately follow this statement, pregnant with
significance, show the deep religious feeling of the author. They read:
"and this I have partly proved and made visible to be seene in some
manner, and God sparing mee life, I will herein make further experience
and that not curiouslie but in the feare of God as neere as He shall
give me grace and meane to annexe the same unto a booke of navigation
which I have had long in hand."--Chap. VIII.
It is evident from the pages of the _Newe Attractive_ (1581) that Norman
was animated with the right spirit of inquiry, which is calm, deliberate
and judicious, which leads to the discovery of facts, to their
coordination and experimental illustration before explanations are
thought of and long before new theories are propounded. The style in
which this little treatise is written has a charm of its own, mainly by
reason of its quaintness. At the end of his address to the candid
reader, which, after the manner of the times, was somewhat belabored and
rhetorical in character, Norman breaks away from common inadequate
prose; and, giving wings to his imagination, writes a lyric on the
magnet which is the first metrical composition in English that we have
on such a subject. It reads:--
THE MAGNES OR LOADSTONE'S CHALLENGE.
Give place ye glittering sparks,
ye glimmering Diamonds bright,
Ye Rubies red, and Saphires brave
wherein ye most delight.
In breefe, yee stones inricht,
and burnisht all with golde,
Set forth in Lapidaries shops,
for Jewells to be sold.
Give place, give place I say,
your beautie, gleame and glee,
Is all the vertue for the which,
accepted so you bee.
Magnes, the Loadstone I,
your painted sheath defie,
Without my help in Indian seas,
the best of you might lie.
I guide the Pilot's course,
his helping hand I am,
The Mariner delights in me,
so doth the Marchant man.
My vertue lies unknowne,
my secrets hidden are,
By me, the Court and Commonweale,
are pleasured very farre.
No ship could sail on Seas,
her course to run aright,
Nor Compass shew the ready way
were Magnes not of might.
Blush then, and blemish all,
bequeath to mee thats due,
Your seats in golde, your price in plate,
which Jewellers do renue.
Its I, its I alone,
whom you usurp upon,
Magnes my name, the Loadstone cal'd,
the prince of stones alone.
If this you can deny,
then seem to make reply,
And let the painfull sea-man judge,
the which of us doth lie.
THE MARINER'S JUDGEMENT.
The Loadstone is the stone,
the onely stone alone,
Deserving praise above the rest
whose vertues are unknown.
THE MARCHANT'S VERDICT.
The Diamonds bright, the Saphires brave,
Are stones that bear the name,
but flatter not, and tell the troath,
Magnes deserves the same.
(Edition of 1720.)
Norman's _Newe Attractive_ was well known to Gilbert, as were also the
_Epistola_ of Peregrinus, the _Magiae Naturalis_ of Porta, and indeed
all books treating of the lodestone, the magnet, or the compass-needle.
His own work _De Magnete_, published in the year 1600, is a compendium
of the world's knowledge of magnetism and electricity at the time. In
its pages, he not only discusses the opinions of others, but describes
discoveries of his own made during the twenty years which he ardently
devoted to the pursuit of experimental science, crowning his
investigations with theories in electricity and magnetism as became a
true philosopher.
Impressed by the originality of Gilbert's treatise, the practical
ingenuity and philosophic acumen displayed throughout, Hallam wrote in
his _Introduction to the Literature of Europe_: "Gilbert not only
collected all the knowledge which others had possessed on the subject,
but became at once the father of experimental philosophy in this island;
and, by a singular felicity and acuteness of genius, the founder of
theories which have been received after the lapse of ages and are almost
universally received into the creed of science."
At a period when natural science was taught in the schools of Europe
mainly from text-books, we find Gilbert proclaiming by example and
advocacy the paramount value of experiment for the advancement of
learning. He was unsparing in his denunciation of the superficiality
and verbosity of mere bookmen, and had no patience with writers who
treated their subjects "esoterically, reconditely and mystically." For
him, the laboratory method was the only one that could secure fruitful
results and contribute effectively to the advancement of learning.
It is true that men of unusual ability and strong character strove
before his time to adjust the claims of authority in matters scientific.
While respectful of the teachings of recognized leaders, they were not,
however, awed into acquiescence by an academical "magister dixit." On
the contrary, they wanted to test with their eyes in order to judge with
reason; believing in the importance of experiment, they sought to
acquire a knowledge of nature from nature herself.
Such were Albert the Great and Friar Bacon. Albert did not bow
obsequiously to the authority of Aristotle or any of his Arabian
commentators; he investigated for himself and became, for his age, a
distinguished botanist, physiologist and mineralogist.
The Franciscan monk of Ilchester has left us in his _Opus Majus_ a
lasting memorial of his practical genius. In the section entitled
"Scientia Experimentalis," he affirms that "Without experiment, nothing
can be adequately known. An argument proves theoretically, but does not
give the certitude necessary to remove all doubt, nor will the mind
repose in the clear view of truth, unless it find it by way of
experiment." And in his _Opus Tertium_: "The strongest arguments prove
nothing, so long as the conclusions are not verified by experience.
Experimental science is the queen of sciences and the goal of all
speculation."
No one, even in our own times, wrote more strongly in favor of the
practical method than did this follower of St. Francis in the
thirteenth century. Being convinced that there can be no conflict
between scientific and revealed truths, he became an irrepressible
advocate for observation and experiment in the study of the phenomena
and forces of nature.
The example of Peregrinus, of Albert and Friar Bacon, not to mention
others like Vincent of Beauvais, the Dominican encyclopedist, was,
however, not sufficient to wean students from the easy-going routine of
book-learning. A few centuries had to elapse before the weaning was
effectively begun; and the man who contributed in a marked degree to
this result was Gilbert the Philosopher of Colchester (1544-1603).
Having received the elements of his education in the Grammar School of
Colchester, his native town, Gilbert entered St. John's College,
Cambridge, from which university he took his B. A. degree in 1560, M. A.
in 1564 and M. D. in 1569. In all, he appears to have been connected
with the University for a period of eleven or twelve years, as student,
Fellow, and examiner.
On leaving Cambridge, Gilbert traveled for four years on the Continent,
principally in Italy, visiting medical schools and studying methods of
treatment under the leading physicians and surgeons of the day as well
as discussing scientific theory with the leaders of thought. On his
return to England in 1573, he practised medicine in London "with great
applause and success." He was elected President of the Royal College of
Physicians in 1599, and appointed Physician to Queen Elizabeth in 1601
and to her successor, James I., in 1603.
On one occasion, he hears that Baptista Porta, whom he calls "a
philosopher of no ordinary note," said that a piece of iron rubbed with
a diamond turns to the north. He suspects this to be heresy. So,
forthwith he proceeds to test the statement by experiment. He was not
dazzled by the reputation of Baptista Porta; he respected Porta, but
respected truth even more. He tells us that he experimented with seventy
diamonds in presence of many witnesses, employing a number of iron bars
and pieces of wire, manipulating them with the greatest care while they
floated on corks; and concludes his long and exhaustive research by
plaintively saying: "Yet never was it granted me to see the effect
mentioned by Porta."
Though it led to a negative result, this probing inquiry was a
masterpiece of experimental work.
Gilbert incidentally regrets that the men of his time "are deplorably
ignorant with respect to natural things," and the only way he sees to
remedy this is to make them "quit the sort of learning that comes only
from books and that rests only on vain arguments and conjectures," for
he shrewdly remarks that "even men of acute intelligence without actual
knowledge of facts and in the absence of experiment easily fall into
error."
Acting on this intimate conviction, he labored for twenty years over the
theories and experiments which he sets forth in his great work on the
magnet. "There is naught in these books," he tells us, "that has not
been investigated, and again and again done and repeated under our
eyes." He begs any one that should feel disposed to challenge his
results to repeat the experiments for himself "carefully, skilfully and
deftly, but not heedlessly and bunglingly."
It has been said that we are indebted to Sir Francis Bacon, Queen
Elizabeth's Chancellor, for the inductive method of studying the
phenomena of nature. Bacon's merit lies in the fact that he not only
minutely analyzed the method, pointing out its uses and abuses, but also
that he showed it to be the only one by which we can attain an accurate
knowledge of the physical world around us. His sententious eulogy went
forth to the world of scholars invested with all the importance,
authority and dignity which the high position and worldwide fame of the
philosophic Chancellor could give it. But while Bacon thought and wrote
in his study, Gilbert labored and toiled in his workshop. By his pen,
Bacon made a profound impression on the philosophic mind of his age; by
his researches, Gilbert explored two provinces of nature and added them
to the domain of science. Bacon was a theorist, Gilbert an investigator.
For twenty years he shunned the glare of society and the throbbing
excitement of public life; he wrenched himself away from all but the
strictest exigencies of his profession, in order to devote himself
undistractedly to the pursuit of science. And all this forty years
before the appearance of Bacon's _Novum Organum_, the very work which
contains the philosopher's "large thoughts and lofty phrases" on the
value of experiment as a means for the advancement of learning. During
that long period Gilbert haunted Colchester, where he delved into the
secrets of nature and prepared the materials for his great work on the
magnet. The publication of this Latin treatise made him known in the
universities at home and especially abroad: he was appreciated by all
the great physicists and mathematicians of his age; by such men as Sir
Kenelm Digby; by William Barlowe, a great "magneticall" man; by Kepler,
the astronomer, who adopted and defended his views; by Galileo himself,
who said: "I extremely admire and envy the author of _De Magnete_."
The science of magnetism owes more to Gilbert than to any other man,
Peregrinus (1269) excepted. He repeated for himself the numerous and
ingenious experiments of the medieval philosopher, and added much of his
own which he discovered during the long period of a life devoted to the
diligent exploration of this domain in the world of natural knowledge.
The ancients spoke of the lodestone as the Magnesian stone, from its
being found in abundance in the vicinity of Magnesia, a city of Asia
Minor. In his Latin treatise of 254 (small) folio pages, Gilbert uses
the adjective form of the term, but never the noun "Magnetismus" itself.
Our English term _magnetism_ appears for the first time on page 2 of
Archdeacon Barlowe's "Magneticall Advertisements," published in 1616;
while the surprising compound, "electro-magnetismos," is the title of a
chapter in Father Kircher's "Magnes, sive de Arte Magnetica," printed in
the year 1641.
Gilbert showed that a great number of bodies could be electrified; but
maintained that those only could exhibit magnetic properties which
contain iron. He satisfies himself of this by rubbing with a lodestone
such substances as wood, gold, silver, copper, zinc, lead, glass, etc.,
and then floating them on corks, quaintly adding that they show "no
poles, because the energy of the lodestone has no entrance into their
interior."
To-day we know that nickel and cobalt behave like iron, whilst antimony,
bismuth, copper, silver and gold are susceptible of being influenced by
powerful electro-magnets, showing what has been termed diamagnetic
phenomena. Even liquids and gases, in Faraday's classical experiments,
yielded to the influence of his great magnet; and Professor Dewar, in
the same Royal Institution, exposed some of his liquid air and liquid
oxygen to the influence of Faraday's electromagnet and found them to be
strongly attracted, thus behaving like the paramagnetic bodies, iron,
nickel and cobalt.
Gilbert observes in all his magnets two points, one near each end, in
which the force, or, as he terms it, "the supreme attractional power,"
is concentrated. Like Peregrinus, he calls these points the _poles_ of
the magnet, and the line joining them its magnetic axis. With the aid of
his steel versorium, he recognizes that similar poles are mutually
hostile, whilst opposite poles seize and hold each other in friendly
embrace. He also satisfies himself that the energy of magnets resides
not only in their extremities, but that it permeates "their inmost
parts, being entire in the whole and entire in each part." This is
exactly what Peregrinus said in 1269 and what we say to-day; it is
nothing else than the molecular theory proposed by Weber, extended by
Ewing and universally accepted.
At any rate, Gilbert is quite certain that whatever magnetism may be, it
is not, like electricity, a material, ponderable substance. He
ascertained this by weighing in the most accurate scales of a goldsmith
a rod of iron before and after it had been rubbed with the lodestone,
and then observing that the weight is precisely the same in both cases,
being "neither less nor more."
Without referring to the prior discovery of Norman, whom he calls "a
skilled navigator and ingenious artificer," Gilbert satisfies himself
that not only the magnet, but all the space surrounding it, possesses
magnetic properties; for the magnet "sends its force abroad in all
directions, according to its energy and quality." This region of
influence Norman called a sphere of "vertue," and Gilbert an "orbis
virtutis," which is the Latin equivalent; we call it a "magnetic field,"
or field of force, which is less expressive and less appropriate. With
wonderful intuition, Gilbert sees this space filled with lines of
magnetic virtue passing out radially from his spherical lodestone, which
lines he calls "rays of magnetic force."
Clerk Maxwell was so fascinated with this beautiful concept that he made
it the work of his life to study the field of force due to electrified
bodies, to magnets and to conductors conveying currents; his powerful
intellect visualized those lines and gave them accurate mathematical
expression in the great treatise on electricity and magnetism which he
gave to the world in 1873.
Gilbert observes that the lodestone may be spherical or oblong;
"whatever the shape, imperfect or irregular, verticity is present; there
are poles," and the lodestones "have the selfsame way of turning to the
poles of the world." He knows that a compass-needle is not drawn bodily
towards the pole, and does not hesitate in this instance to give credit
to his countryman, Robert Norman, for having clearly stated this fact
and aptly demonstrated it. Following Norman, he floats a needle in a
vessel by means of a piece of cork, and notices that on whatever part of
the surface of the water it may be placed, the needle settles down after
a few swings invariably in the same direction. His words are: "It
revolves on its iron center and is not borne towards the rim of the
vessel."
Gilbert knew nothing about the mechanical couple that came into play,
but he knew the fact; and, with the instinct of the philosopher, tested
it in a variety of ways.
We explain the orientation of the compass-needle by saying that it is
acted upon by a pair of equal and opposite forces due to the influence
of the terrestrial magnetic poles on each end of the needle and by
showing that such a couple can produce rotation, but not translation.
We find Gilbert working not only with steel needles and iron bars, but
also with rings of iron. He strokes them with a natural magnet and feels
certain that he has magnetized them. He assures us that "one of the
poles will be at the point rubbed and the other will be at the opposite
side." To show that the ring is really magnetized, he cuts it across,
opens it out, and finds that the ends exhibit polar properties.
A favorite piece of apparatus with Gilbert, as with Peregrinus, was a
lodestone ground down into globular form. He called it a terrella, a
miniature earth, and used it extensively for reproducing the phenomena
described by magnetizers, travelers and navigators. He breaks up
terrellas, in order to examine the magnetic condition of their inner
parts. There is not a doubtful utterance in his description of what he
finds; he speaks clearly and emphatically. "If magnetic bodies be
divided, or in any way broken up, each several part hath a north and a
south end"; _i.e._, each part will be a complete magnet.
[Illustration: FIG. 8 Behavior of compass-needle on a _terrella_ or
spherical lodestone]
We find him also comparing magnets by what is known to us as the
"magnetometer method." He brings the magnetized bars in turn near a
compass-needle and concludes that the magnet or the lodestone which is
able to make the needle go round is the best and strongest. He also
seeks to compare magnets by a process of weighing, similar to what is
called, in laboratory parlance, the "test-nail" method. He also inquires
into the effect of heat upon his magnets, and finds that 'a lodestone
subjected to any great heat loses some of its energy.' He applies a
red-hot iron to a compass-needle and notices that it 'stands still, not
turning to the iron.' He thrusts a magnetized bar into the fire until it
is red-hot and shows that it has lost all magnetic power. He does not
stop at this remarkable discovery, for he proceeds to let his red-hot
bars cool while lying in various positions, and finds: (1) that the bar
will acquire magnetic properties if it lie in the magnetic meridian; and
(2) that it will acquire none if it lie east and west. These effects he
rightly attributes to the inductive action of the earth.
Gilbert marks these and other experiments with marginal asterisks; small
stars denoting minor and large ones important discoveries of his. There
are in all 21 large and 178 small asterisks, as well as 84 illustrations
in _De Magnete_. This implies a vast amount of original work, and forms
no small contribution to the foundations of electric and magnetic
science.
Gilbert clearly realized the phenomena and laws of magnetic induction.
He tells us that "as soon as a bar of iron comes within the lodestone's
sphere of influence, though it be at some distance from the lodestone
itself, the iron changes instantly and has its form renewed; it was
before dormant and inert; but now is quick and active." He hangs a nail
from a lodestone; a second nail from the first, a third from the second
and so on--a well-known experiment, made every day for elementary
classes. Nor is this all, for he interposes between the lodestone and
his iron nail, thick boards, walls of pottery and marble, and even
metals, and he finds that there is naught so solid as to do away with
its force or to check it, save a plate of iron. All that can be added to
this pregnant observation is that the plate of iron must be very thick
in order to carry all the lines of force due to the magnet, and thus
completely screen the space beyond.
But Gilbert is astonishing when he goes on to make thick boxes of gold,
glass and marble; and, suspending his needle within them, declares with
excusable enthusiasm that, regardless of the box which imprisons the
magnet, it turns to its predestined points of north and south. He even
constructs a box of iron, places his magnet within, observes its
behavior, and concludes that it turns north and south, and would do so
were "it shut up in iron vaults sufficiently roomy." In this, he was in
error, for experiments show that if the sides of the box are thin, the
needle will experience the directive force of the earth; but if they are
sufficiently thick--thick as the walls of an ordinary safe--the inside
of such a box will be completely screened; none of the earth's magnetic
lines will get into it so that the needle will remain indifferently in
any position in which it is placed. Some years ago, the physical
laboratory of St. John's College, Oxford, was screened from the
obtrusive lines of neighboring dynamos by building two brick walls
parallel to each other and eight inches apart and filling in the space
with scrap iron. A delicate magnetometer showed that such a structure
allowed no leakage of lines of force through it, but offered an
impenetrable barrier to the magnetic influence of the working dynamos.
Gilbert's greatest discovery is that the earth itself acts as a vast
globular magnet having its magnetic poles, axis and equator. The pole
which is in our hemisphere, he variously calls north, boreal or arctic.
Whilst that in the other hemisphere he calls south, austral or
antarctic. He sought to explain the magnetic condition of our globe by
the presence, especially in its innermost parts, of what he calls true,
terrene matter, homogeneous in structure and endowed with magnetic
properties, so that every separate fragment exhibits the whole force of
magnetic matter. He is quite aware that his theory is a grand
generalization; and admits that it is "a new and till now unheard-of
view," and so confident is he in its worth that he is not afraid to say
that "it will stand as firm as aught that ever was produced in
philosophy, backed by ingenious argumentation or buttressed by
mathematical demonstration."
In developing his theory of terrestrial magnetism, Gilbert fell into
certain errors, chiefly for want of data, but partly also by reason of
his adherence to the view that the earth exactly resembled his terrella
in its magnetic action. Accordingly, he believed that the magnetic poles
of the earth were diametrically opposite each other and that they
coincided with the poles of rotation, whence it followed that the
magnetic meridian everywhere coincided with the geographical, and that
the magnet, unless influenced by local disturbances, stood true to the
pole.
It was, however, well known from the thrilling experience of Columbus
and the constant report of travelers that this was not the case. Gilbert
himself says that at the time of writing, in the year 1600, the needle
pointed 11-1/3° east of north in London; but what he did not know and
could not have known was that this easterly deviation was decreasing
from year to year, to vanish altogether in 1657, after which the needle
began to decline to the west.
This magnetic declination sorely perplexed Gilbert, as it did not fit in
with his theory. Yet an explanation was needed; and as the earth must be
considered a normal and well-behaved magnet, though of cosmical size,
Gilbert turns the difficulty by saying that this variation is nothing
else than "a sort of perturbation of the directive force" caused by
inequalities in the earth's surface by continents and mountain masses:
"Since the earth's surface is diversified by elevations of land and
depths of seas, great continental lands, oceans and seas differing in
every way while the power that produces all magnetic movements comes
from the constant magnetic earth-substance which is strongest in the
most massive continent and not where the surface is water or fluid or
unsettled, it follows that toward a massive body of land or continent
rising to some height in any meridian, there is a measurable magnetic
leaning from the true pole toward the east or the west."
So convinced is Gilbert of the true and satisfactory character of his
explanation that he goes on to say that, "In northern regions, the
compass varies because of the northern eminences; in southern regions,
because of southern eminences. On the equator, if the eminences on both
sides were equal, there would be no variation." In a later chapter of
Book IV., he adds that, "in the heart of great continents there is no
variation; so, too, in the midst of great seas."
As continents and mountain-chains are among the permanent features of
our planet, Gilbert concluded that the misdirection of the needle was
likewise permanent or constant at any given place, a conclusion which
observations made after Gilbert's time showed to be incorrect. Gilbert
writes: "As the needle hath ever inclined toward the east or toward the
west, so even now does the arc of variation continue to be the same in
whatever place or region, be it sea or continent; so, too, will it be
forever unchanging."
This we know to be untrue, and Gilbert, too, could have known as much
had he brought the experimental method, which he used with such
consummate skill and fruitful results in other departments of his
favorite studies, to bear on this particular element of terrestrial
magnetism. He labored with incredible ardor and persistence for twenty
years in his workshops at Colchester over the experiments in
electricity, magnetism and terrestrial magnetism which he embodies and
discusses in his original and epoch-making book, _De Magnete_, published
in the year 1600; a period of twenty years was long enough for such a
careful observer as he was to detect the slow change in magnetic
declination discovered by his friend Gellibrand in 1634, published by
him in 1635, and known to-day as the "secular variation." It is true the
quantity to be measured was small; but what is surprising is that such
an industrious and resourceful experimenter as Gilbert was does not
record in his pages any observations of his own on declination or dip,
elements of primary importance in magnetic theory.
Shortly after the voyage of Columbus it was thought that the _longitude_
of a place could be found from its magnetic declination. Gilbert,
however, did not think so, and accordingly scores those who championed
that view. "Porta," he says, "is deluded by a vain hope and a baseless
theory"; Livius Sanutus "sorely tortures himself and his readers with
like vanities"; and even the researches of Stevin, the great Flemish
mathematician, on the cause of variation in the southern regions of the
earth are "utterly vain and absurd."
With regard to dip, Gilbert erroneously held that for any given latitude
it had a constant value. He was so charmed with this constancy that he
proposed it as a means of determining _latitude_. There is no diffidence
in his mind about the matter; he is sure that with his "inclinatorium"
or dip-circle, together with accompanying tables, calculated for him by
Briggs, of logarithmic fame, an observer can find his latitude "in any
part of the world without the aid of the sun, planets or fixed stars in
foggy weather as well as in darkness."
After such a statement, it is no wonder that he waxes warm over the
capabilities of his instrument and allows himself to exclaim: "We can
see how far from idle is magnetic philosophy; on the contrary, how
delightful it is, how beneficial, how divine! Seamen tossed by the waves
and vexed with incessant storms while they cannot learn even from the
heavenly luminaries aught as to where on earth they are, may with the
greatest ease gain comfort from an insignificant instrument and
ascertain the latitude of the place where they happen to be."
Gilbert dwells at length on the inductive action of the earth. He
hammers heated bars of iron on his anvil and then allows them to cool
while lying in the magnetic meridian. He notes that they become
magnetized, and does not fail to point out the polarity of each end. He
likewise attributes to the influence of the earth the magnetic condition
acquired by iron bars that have for a long time lain fixed in the
north-and-south position and ingenuously adds: "for great is the effect
of long-continued direction of a body towards the poles." To the same
cause, he attributes the magnetization of iron crosses attached to
steeples, towers, etc., and does not hesitate to say that the foot of
the cross always acquires north-seeking polarity.
In a similar manner, every vertical piece of iron, like railings,
lamp-posts, and fire-irons, becomes a magnet under the inductive action
of the earth. In the case of our modern ships, the magnetization of
every plate and vertical post, intensified by the hammering during
construction, converts the whole vessel into a magnetic magazine, the
resulting complex "field" rendering the adjustment of the compasses
somewhat difficult and unreliable. The unreliable character of the
adjustment arises mainly from the changing magnetism of the ship with
change of place in the earth's magnetic field, the effect increasing
slightly from the magnetic equator to the poles.
With luminous insight into the phenomena of terrestrial magnetism,
Gilbert observes that in the neighborhood of the poles, a
compass-needle, tending as it does to dip greatly, must in consequence
experience only a feeble directive power. To which he adds that "at the
poles there is no direction," meaning, no doubt, that a compass-needle
would remain in any horizontal position in which it might be placed when
in the vicinity of the magnetic pole.
This is precisely the experience of all Arctic explorers, who find that
their compasses become less and less active as they sail northward, the
reason being that the horizontal component of the earth's magnetic
force, which alone controls the movements of the compass-needle,
decreases as the ship advances and vanishes altogether at the magnetic
pole. When once a high latitude is reached, captains do not depend upon
their compasses for their bearings, but have recourse to astronomical
observations. In his account of magnetic work carried on in the
neighborhood of the magnetic pole, Amundsen says: "At Prescott Island
the compass, which for some time had been somewhat sluggish, refused
entirely to act, and we could as well have used a stick to steer by."
As a physician, Gilbert valued iron for its medicinal properties, but
denounced quacks and wandering mountebanks who practised "the vilest
imposture for lucre's sake," using powdered lodestone for the cure of
wounds and disorders. "Headaches," he said, "are no more cured by
application of a lodestone than by putting on an iron helmet or a steel
hat"; and again: "To give it in a draught to dropsical persons is either
an error of the ancients or an impudent tale of their copyists."
Elsewhere he condemns prescriptions of lodestone as "an evil and deadly
advice" and as "an abominable imposture."
In the sixth and last book of _De Magnete_, Gilbert sets forth his views
on such astronomical subjects as the figure of the earth, its
suspension in space, rotation on its axis and revolution around the sun.
As to the figure of our planet, the primitive view widely credited in
early times was that the earth is a flat, uneven mass floating in a
boundless ocean. The Hindoos, however, did not accept the flatland
doctrine, but taught that the earth was a convex mass which rested on
the back of a triad of elephants having for their support the carapace
of a gigantic tortoise. Of course, they did not say how the complaisant
chelonian contrived to maintain his wonderful state of equilibrium under
the superincumbent mass.
Aristotle (384-322, B. C.) taught that the earth, fixed in the center of
the universe, is not flat as a disk, but round as an orange, giving as
proofs (1) the gradual disappearance of a ship standing out to sea and
(2) the form of the shadow cast by the earth in lunar eclipses, to which
others added (3) the change in the altitude of circumpolar stars readily
noticeable in traveling north or south. Aristarchus of Samos (310-250),
one of the great astronomers of antiquity, went further, not fearing to
teach that the earth is spherical in form, that it turns on its axis
daily and revolves annually around the sun. Such orthodox teaching did
not, however, commend itself to people generally, as they did not
exactly like the idea of being whisked round with their houses and
cities at a dangerous speed, preferring to explain celestial phenomena
by the rotation of the vast celestial sphere, with all the starry host,
round a flat, immovable earth. For them such a system of cosmography
recommended itself by its simplicity and reasonableness as well as by
the sense of stability, rest and comfort which it brought along with it.
Ptolemy, who flourished at Alexandria about 150 A. D. and whose name is
associated with a system of the world, also held that the earth is
spherical in form, giving at the same time some very ingenious proofs of
his belief. St. Augustine, in the fourth century, was not opposed to the
doctrine of a round earth, though he felt the religious difficulty
arising from the existence of the antipodes, which difficulty reached
its acute stage four hundred years later.
It is well to remember that the Church did not condemn the existence of
an antipodean world; what it did condemn was the teaching of Virgilius,
Bishop of Salzburg, to the effect that this world, lying under the
equator, was inhabited by a race of men not descended from Adam.
Virgilius also taught that the antipodes had a sun and moon different
from ours, an astronomical opinion for which he was never molested by
ecclesiastical authority.
Boethius, the worthy representative of the natural and the higher
philosophy of the sixth century, wrote of the earth as globe-like in
form, but small in comparison with the heavens. Isidore of Seville, in
the seventh century, "the most learned man of his age," and the
encyclopedic Bede, in the eighth, rejected the theory of a flat,
discoidal earth and returned to the spherical form of the early Greek
astronomers. But again, centuries had to elapse before people could be
brought to tolerate views of the world that seemed so directly opposed
to the daily testimony of their senses.
The strong, conclusive arguments which alone establish this theory on a
firm basis were, however, not known to Copernicus and could not have
been known in an age that preceded the invention of the telescope and in
which the astronomer had to be the constructor of his own crude wooden
instruments. The wonder is that Copernicus did such excellent
observational work on the banks of the Vistula with the rough appliances
at his disposal. The arguments which he put forward and urged with
consummate skill for the acceptance of his revolutionary theory were its
general simplicity and probability. Of proofs clear and decisive, he
gave none; yet, while he was working on his epoch-making treatise, begun
in 1507 and published in 1543 with dedication to Pope Paul III., a
direct proof of the earth's spherical form was given by the return
(1528) from the Philippines along an eastern route of one of Magellan's
ships, which had reached those distant isles after crossing the western
ocean, which the Portuguese navigator called the "Pacific," from the
tranquility of its waters. For a direct proof of the earth's _annual_
motion, the world had to wait two hundred years more, until Bradley
discovered the "aberration of light" in 1729; and for a direct
demonstration of its _diurnal_ motion until Foucault made his pendulum
experiment in the Panthéon, in 1851.
We cannot let Gilbert's reference to a "weightless earth" pass without a
few remarks to justify our approval of the statement.
The idea connoted by the term weight is the pull which the earth exerts
on the mass of a body; thus, when we say that an iron ball weighs six
pounds, we mean that the earth pulls it downwards with a force equal to
the weight of six pounds. That the weight of a given lump of matter is
not a constant but a dependent quantity may be seen from a number of
considerations. Its weight in vacuo, for instance, is different from its
weight in air, and this latter differs considerably from its weight in
water or in oil. Again, if we take our experimental ball down the shaft
of a mine, the spring-balance used to measure the pull of the earth on
it will not record six pounds but something less; and the further we
descend, the less will the spring-balance be found to register. At a
depth of two thousand miles below the surface, the ball would be found
to have lost half its weight; and at a depth of four thousand, all its
weight. At the earth's center a "box of weights" would still be called a
"box of weights," though neither the box itself nor its enclosed
standards singly or collectively would have any weight whatever. It has
been shown experimentally that two masses weigh slightly less when
placed one above the other than when placed side by side, because in the
latter case their common mass-center is measurably nearer to the center
of the earth. Every mother knows that when a boy is sent to buy a pound
of candy, it is the mass of the sweet stuff that makes him happy, and
not its weight, for this acts more like an incumbrance while he is
bringing it home. Of course, weight is every day used, and correctly, as
a measure of mass, for every student of mechanics writes without the
least hesitation,
W=Mg.
by which he simply means that the weight of a body is directly
proportional to its mass (M), which is constant wherever the body may be
taken, and to the intensity of gravity (g), which varies slightly with
geographical position. As both scale-pans of an ordinary balance are
equally affected by the local value of _g_, it follows that equilibrium
is established only when the two _masses_--that of the body and that of
the standards--are themselves equal: hence weighing is in reality only a
process of comparing masses, _i.e._, a process of "massing."
If we bring our experimental ball to the top of a hill or to the summit
of a mountain or aloft in a balloon, we find the pull on the registering
spring growing less and less as we go higher and higher, from which we
naturally conclude that if we could go far enough out into
circumterrestrial space, say, towards the moon, the ball would lose its
weight entirely; it would cease to stretch the spring of the measuring
balance, its weight vanishing at a definite, calculable distance from
the earth's center. If carried beyond that point the ball would come
under the moon's preponderating attraction and would begin to depress
anew the index of the balance until at the surface of our satellite it
would be found to weigh exactly _one_ pound. If transferred to the
planet Mars the ball would weigh _two_ pounds, and if to the surface of
the giant planet Jupiter, _sixteen_ pounds. But while its weight thus
changes continually, its mass or quantity of matter, the stuff of which
it is made, remains constant all the while, being equally unaffected by
such variables as motion, position or even temperature.
Returning from celestial space to our more congenial terrestrial
surroundings, we find a similar inconstancy in the weight of the ball as
we travel from the equator toward either pole, the weight being least at
the equator and slightly greater at either end of our axis of rotation.
This change is fully accounted for by the spheroidal figure of the earth
and its motion of rotation, in virtue of which, while going from the
equator toward the pole, our distance from the center of attraction
undergoes a slight diminution, as does also the component of the local
centrifugal force, which is in opposition to gravity.
From all this, it will be seen that the weight of a body is more of the
nature of an accidental rather than an essential property of matter,
whereas its mass is a necessary and unvarying property. Hence we speak
with propriety of the conservation of mass just as we speak with equal
propriety of the conservation of energy; but we may never speak or write
of the conservation of weight. The mass of our iron ball is precisely
the same away from the surface of the earth as it is anywhere on the
surface, whether a thousand miles below the surface or a thousand miles
above it; and the same it would be found in any part of the solar system
or of the starry universe to which it might be taken.
Since weight is nothing else than the pull which the earth exerts on a
body, it follows that, big and massive as our planet is, it must,
nevertheless, be weightless; for it cannot with any degree of propriety
be said to pull itself. It is incapable of producing even an
infinitesimal change in the position of its mass-center, or center of
gravity, as this centroid is sometimes called. The earth attracts
_itself_ with no force whatever; but is attracted and governed in its
annual movement by the sun, the central controlling body of our system,
while the moon and planets play only the part of petty disturbers.
It would, however, be right to speak of the _weight_ of the earth
_relatively_ to the sun; for the sun attracts the mass of our planet
with a certain definite force, readily calculable from the familiar
formula for central force, viz., mv^2/r., in which _m_ is the mass of
the earth, _v_ its orbital velocity and _r_ its distance from the sun.
Supplying the numbers, the weight of the earth relatively to the sun,
comes out to be
3,000000,000000,000000 or 3×10^{18} tons weight,
or, in words, three million million million tons weight.
It may here be noted that the velocity _v_ of the earth in its orbit is
a varying quantity, depending on distance from the sun. As this distance
is least in December and greatest in June, it follows that the earth is
heavier relatively to the sun in winter than it is in summer.
The _mass_ of the earth, on the other hand, is not a relative and
variable quantity, but a constant and independent one, which would not
be affected either by the sudden annihilation of all the other members
of the solar system or by the instantaneous or successive addition of a
thousand orbs. Mass being the product of volume by density, that of the
earth is 6000,000000,000000,000000 or 6×10^{21} tons mass, which reads
six thousand million million million tons mass.
The number which expresses the mass of the earth is thus very different
from that which represents its weight relatively to the sun. It is
obvious that the latter would be a much greater quantity if our planet
were transferred to the orbit of Venus and very much less if transferred
to that of far-off Jupiter, but the number which expresses its _mass_
would remain precisely the same in both cases, viz., the value given
above.
In elaborating his theory of magnetism, and especially his magnetic
theory of the earth, Gilbert made extensive use of lodestone-globes,
which he called "terrellas," _i.e._, miniature models of the earth. In
pursuing his searching inquiry, he was gradually led from these
"terrellas" to his great induction that the earth itself is a colossal,
globe-like magnet. Following Norman, "the ingenious artificer," of
Limehouse, London, he also showed that the entire cubical space which
surrounds a lodestone is an "orb of virtue," or region of influence,
from which he inferred that the earth itself must have its "orb of
virtue," or magnetic field, extending outward to a very great distance.
Gilbert does not, for a moment, think that this theory of terrestrial
magnetism, the first ever given to the world, is a wild speculation. Far
from it; he is convinced that "it will stand as firm as aught that ever
was produced in philosophy, backed by ingenious argumentation or
buttressed by mathematical demonstration."
If the earth has a magnetic field, he argued, why not the moon, the
planets and the sun itself, "the mover and inciter of the universe"?
Given these planetary magnetic fields, Gilbert seems to have no
difficulty in finding out the forces necessary to account for the
crucial difficulties of the Copernican doctrine. Nor is the medium
absent that is needed for the mutual action of magnetic globes, for we
are assured that it is none other than the universal _ether_, which, he
says "is without resistance."
Gilbert disposes of the cosmographic puzzle of the "suspension" of the
earth in space by saying, and saying justly, that the earth "has no
heaviness of its own," and, therefore, "does not stray away into every
region of the sky." To emphasize the statement, he continues: "The
earth, in its own place, is in no wise heavy, nor does it need any
balancing"; and again, "The whole earth itself has no weight." "By the
wonderful wisdom of the Creator," he elsewhere says, "forces were
implanted in the earth that the globe itself might with steadfastness
take direction."
Gilbert holds that the daily rotation of the earth on its axis is also
caused, and maintained with strict uniformity, by the same prevalent
system of magnetic forces, for "lest the earth should in divers ways
perish and be destroyed, she rotates in virtue of her _magnetic energy_,
and such also are the movements of the rest of the planets."
Just how this magnetic energy acts to produce the rotatory motion of a
massive globe Gilbert does not say. Nor was he able to solve such a
magnetic riddle, for there was nothing in his philosophy to explain how
a lodestone-globe in free space should ever become a perpetual magnetic
motor. Oddly enough he disagrees with Peregrinus, who maintained in his
_Epistola_, 1269, that a terrella, or spherical lodestone, poised in the
meridian, would turn on its axis regularly every 24 hours. He naively
says: "We have never chanced to see this; nay, we doubt if there is such
a movement." Continuing, he brings out his clinching argument: "This
daily rotation seems to some philosophers wonderful and incredible
because of the ingrained belief that the mighty mass of earth makes an
orbital movement in 24 hours; it were more incredible that the moon
should in the space of 24 hours traverse her orbit or complete her
course; more incredible that the sun and Mars should do so; still more
that Jupiter and Saturn; more than wonderful would be the velocity of
the fixed stars and firmament."
Here he finds himself obliged to berate Ptolemy for being "over-timid
and scrupulous in apprehending a break up of this nether world were the
earth to move in a circle. Why does he not apprehend universal ruin,
dissolution, confusion, conflagration and stupendous celestial and
super-celestial calamities from a motion (that of the starry sphere)
which surpasses all imagination, all dreams and fables and poetic
license, a motion ineffable and inconceivable?"
Gilbert is not clear and emphatic on the other doctrine of Copernicus,
the revolution of the earth and planets around the sun. He does,
however, say that each of the moving globes "has circular motion either
in a great circular orbit or on its own axis, or in both ways." Again:
"The earth by some great necessity, even by a virtue innate, evident and
conspicuous, is turned circularly about the sun." Elsewhere he affirms
that the moon circles round the earth "by a magnetic compact of both."
He returns to this point in his _De Mundo Nostro_, saying, "The force
which emanates from the moon reaches to the earth; and, in like manner,
the _magnetic virtue_ of the earth pervades the region of the moon."
We have here an implied interaction between two magnetic fields, rather
a clever idea for a magnetician of the sixteenth century. In one case,
the reaction is between the field of the earth and that of the moon,
compelling the latter to rotate round its primary once every month; and
the second, between the field of the earth and that of the sun,
compelling our planet to revolve round the center of our system once
every year.
Though an inefficient cause of the annual motion of our planet, this
interaction of two magnetic fields had, nevertheless, something in
common with the idea of the mutual action of material particles
postulated in the Newtonian theory of universal gravitation.
This magnetic assumption by which Gilbert sought to defend the theory of
the universe propounded by Copernicus was a very vulnerable point in
his astronomical armor which was promptly detected and fiercely assailed
by a galaxy of continental writers; all of them churchmen, physicists
and astronomers of note. They accepted Gilbert's electric and magnetic
discoveries and warmed up to his experimental method; they did not
discard his theory of terrestrial magnetism, but rejected and scoffed at
the use which he made of it to justify the heliocentric theory. They
poked fun at the English philosopher for his magnetic hypothesis of
planetary rotation and revolution, and succeeded in discrediting the
Copernican doctrine. Error prevailed for a time, but Newton's
_Principia_, published in 1687, gave the Ptolemaic system the _coup de
grâce_. Gilbert's hypothesis of the interaction of planetary magnetic
fields gave way to universal gravitation, and Copernicanism was finally
triumphant.
Throughout the pages of Gilbert's treatise, he shows himself remarkably
chary in bestowing praise, but surprisingly vigorous in denunciation.
St. Thomas is an instance of the former, for it is said that he gets at
the nature of the lodestone fairly well; and it is admitted that "with
his godlike and perspicacious mind, he would have developed many a point
had he been acquainted with magnetic experiments." Taisnier, the
Belgian, is an example of the latter, whose plagiarism from Peregrinus
wrings from our indignant author such withering words as "May the gods
damn all such sham, pilfered, distorted works, which so muddle the minds
of students!"
Besides his treatise on the magnet, Gilbert is the author of an
extensive work entitled, "De Mundo Nostro Sublunari," in which he
defends the modern system of the universe propounded by Copernicus and
gives his views on important cosmical problems. This work was published
after the author's death, first at Stettin in 1628, and again at
Amsterdam in 1651.
Chancellor Bacon was well acquainted with this treatise of our
philosopher; indeed he had in his collection the only two manuscript
copies ever made, one in Latin and the other in English, a very singular
and significant fact in view of the Chancellor's attitude toward
Gilbert. Putting it crudely, one would like to know how he obtained
possession of the manuscripts and what was his motive in keeping them
hidden away from the philosophers of the day. "It is considered
surprising," writes Prof. Silvanus P. Thompson, "that Bacon, who had the
manuscripts in his possession and held them for years unpublished,
should have written severe strictures upon their dead author and his
methods, while at the very same time posing as the discoverer of the
inductive method in science, a method which Gilberd (Gilbert) had
practised for years before."[7]
That Bacon was no admirer of Gilbert's physical and cosmical theories
the following passages will show. In the "Novum Organum" the Chancellor
wrote: "His philosophy is an instance of extravagant speculation founded
on insufficient data"; again, "As the alchemists made a philosophy out
of a few experiments of the furnace, Gilbert, our countryman, hath made
a philosophy out of the lodestone" ("The Advancement of Learning");
lastly, "Gilbert hath attempted a general system on the magnet,
endeavoring to build a ship out of materials not sufficient to make the
rowing-pins of a boat" ("De Augmentis Scientiarum").
One is tempted to ask how this strange disregard which Bacon entertained
for the scientific views of the greatest natural philosopher of his age
and country came to exist? Was it due to a feeling of jealousy that
could not brook a rival in the domain of the higher philosophy, or was
it because Bacon, the anti-Copernican, wanted to write down Gilbert, the
defender of the heliocentric theory, in the British Isles?
When reading Bacon's depreciatory remarks we have to remember that his
mathematical and physical outfit was very limited even for the age in
which he lived; from which it is safe to infer that he was but little
qualified to pass judgment on the value of the electric and magnetic
work accomplished in the workshops at Colchester or on the theories to
which they gave rise.
Bacon deserves praise for denouncing the prevalent system of natural
philosophy which was mainly authoritative, speculative and syllogistic
instead of experimental, deductive and inductive, but he was
inconsistent and forgetful of his own principles when he belittled the
greatest living enemy of mere book-learning, and the most earnest
advocate, by word and example, of the laboratory methods for the
advancement of learning.
To avoid misapprehension, it should be here stated that Bacon was not
always censorious in his treatment of his illustrious fellow-citizen,
for in several places he writes approvingly of the electric and magnetic
experiments contained in _De Magnete_, which he calls in his
_Advancement of Learning_, "a painfull (_i.e._, painstaking)
experimentall booke." In other places he draws so freely on Gilbert
without acknowledgment as to come dangerously near the suspicion of
plagiarism.
Gilbert died, probably of the plague, in the sixtieth year of his age,
on December 10th, 1603, and was buried in the chancel of Holy Trinity
Church, Colchester, where a mural tablet records in Latin the chief
facts of his life.
Dr. Fuller in his "Worthies of England" (1662) describes Gilbert as tall
of stature and cheerful of "complexion," a happiness, he quaintly
remarks, not ordinarily found in so hard a student and retired a
person." Concluding his appreciation of the philosopher, Fuller writes:
"Mahomet's tomb at Mecha[6] is said strangely to hang up, attracted by
some invisible loadstone; but the memory of this Doctor will never fall
to the ground, which his incomparable book _De Magnete_ will support to
eternity."
Animated by a similar spirit of national pride, Dryden wrote
Gilbert shall live till loadstones cease to draw,
Or British fleets the boundless ocean awe.
We shall close these remarks by Hallam's estimate of Gilbert as a
scientific pioneer, contained in his _Introduction to the Literature of
Europe_. "The year 1600," he says, "was the first in which England
produced a remarkable work in physical science; but this was one
sufficient to raise a lasting reputation for its author. Gilbert, a
physician, in his Latin treatise on the magnet, not only collected all
the knowledge which others had possessed on the subject, but became at
once the father of experimental philosophy in this island; and, by a
singular felicity and acuteness of genius, the founder of theories which
have been revived after a lapse of ages and are almost universally
received into the creed of science."
For well-nigh three hundred years, _De Magnete_ remained untranslated,
being read only by the scholarly few. The first translation was made by
P. Fleury Mottelay, of New York, and published by Messrs. Wiley and Sons
in the year 1893. Mr. Mottelay has given much attention to the
bibliography of the twin sciences of electricity and magnetism, as the
foot-notes which he has added to the translation abundantly prove.
A second translation appeared in the tercentenary year, 1900, and was
the work of the members of the Gilbert Club, London, among whom were Dr.
Joseph Larmor and Prof. Silvanus P. Thompson. It is a page-for-page
translation with facsimile illustrations, initial letters and
tail-pieces.
As one would infer from the numerous references contained in _De
Magnete_, Gilbert had a considerable collection of valuable books,
classical and modern, bearing on the subject of his life-work; but
these, as well as his terrellas, globes, minerals and instruments,
perished in the great fire of London, 1666, with the buildings of the
College of Physicians, in which they were located.
A portrait of Gilbert was preserved in the Bodleian Library, Oxford, for
many years; but has long since disappeared from its walls. On the
occasion of the three hundredth anniversary (1903) of Gilbert's death, a
fine painting representing the Doctor in the act of showing some of his
electrical experiments to Queen Elizabeth and her court (including Sir
Walter Raleigh, Sir Francis Drake and Cecil, Lord Burleigh, famous
Secretary of State), was presented to the Mayor of Colchester by the
London Institute of Electrical Engineers. A replica of the painting was
sent to the St. Louis Exposition, 1904, where it formed one of the
attractions of the Electricity Building.
The house in which Gilbert was born (1544) still stands in Holy Trinity
Street, Colchester, where it is frequently visited by persons interested
in the history of electric and magnetic science.
BROTHER POTAMIAN.
FOOTNOTES:
[6] "Souvenir of Gilberd's Tercentenary," p. 6.
[7] See magnetic myths, page 5.
CHAPTER III.
FRANKLIN AND SOME CONTEMPORARIES.
As already seen, the writers of Greece and Rome knew little about the
lodestone; we have now to add that the knowledge of electricity which
they possessed was of the same elementary character. They knew that
certain resinous substances, such as amber and jet had, when rubbed, the
property of attracting straws, feathers, dry leaves and other light
bodies; beyond this, their philosophy did not go. The Middle Ages added
little to the subject, as the Schoolmen were occupied with questions of
a higher order. The Saxon Heptarchy came and went, Alcuin taught in the
schools of Charlemagne, Cardinal Langton compelled a landless and
worthless king to sign Magna Charta, universities were founded with
Papal sanction in Italy, France, Germany, England and Scotland,
Copernicus wrote his treatise on the revolution of heavenly bodies and
dedicated it to Pope Paul III., Tycho Brahé made his famous astronomical
observations at Uranienborg and befriended at Prague the penniless
Kepler, and Columbus gave a New World to Castile and Leon--all this
before the man appeared who, using amber as guide, discovered a new
world of phenomena, of thought and philosophy. This man was no other
that Gilbert, whose discoveries in magnetism were described in an
earlier chapter. The trunk line of his work was magnetism; electricity
was only a siding. One was the main subject of a life-long quest while
the other was only a digression. It was a digression in which the
qualities of the native-born investigator are seen at their very best:
alertness and earnestness, resourcefulness and perseverance, all
rewarded by a rich harvest of valuable results. It is refreshing and
inspiring to read the Second Book of Gilbert's treatise, _De Magnete_,
in which are recorded in quick succession the twenty important
discoveries which he made in his new field of labor.
[Illustration: FIG. 9 Gilbert's "versorium" or electroscope]
At the very outset, he found it necessary to invent a recording
instrument to test the electrification produced by rubbing a great
variety of substances. This he appropriately called a _versorium_; we
would call it an electroscope. "Make to yourself," he says, "a rotating
needle of any sort of metal three or four fingers long and pretty light
and poised on a sharp point." He then briskly rubs and brings near his
versorium glass, sulphur, opal, diamond, sapphire, carbuncle,
rock-crystal, sealing-wax, alum, resin, etc., and finds that all these
attract his suspended needle, and not only the needle, but everything
else. His words are remarkable: "All things are drawn to electrics."
Here is a great advance on the amber and jet, the only two bodies
previously known as having the power to attract "straws, chaff and
twigs," the usual test-substances of the ancients. Pursuing his
investigations, he finds numerous bodies which perplex him, because when
rubbed they do not affect his electroscope. Among these, he enumerates:
bone, ivory, marble, flint, silver, copper, gold, iron, even the
lodestone itself. The former class he called _electrica_, electrics; the
latter was termed _anelectrica_, non-electrics.
To Gilbert we, therefore, are indebted for the terms electric and
electrical, which he took from the Greek name for amber instead of
succinic and succinical, their Latin equivalents. The noun electricity
was a coinage of a later period, due probably to Sir Thomas Browne, in
whose _Pseudodoxia Epidemica_, 1646, it occurs in the singular number on
page 51 and in the plural on page 79. It may interest the reader to be
here retold that we owe the chemical term _affinity_ to Albertus Magnus,
_barometer_ to Boyle, _gas_ to van Helmont, _magnetism_ to Barlowe,
magnetic _inclination_ to Bond, electric _circuit_ to Watson, electric
_potential_ to Green, _galvanometer_ to Cumming, _electro-magnetism_ to
Kircher, _electromagnet_ to Sturgeon, and _telephone_ to Wheatstone.
Gilbert was perplexed by the anomalous behavior of his non-electrics. He
toiled and labored hard to find out the cause. He undertook a long,
abstract, philosophical discussion on the nature of bodies which, from
its very subtlety, failed to reveal the cause of his perplexing
anomaly. Gilbert failed to discover the distinction between conductors
and insulators; and, as a consequence, never found out that similarly
electrified bodies repel each other. Had he but suspended an excited
stick of sealing-wax, what a promised land of electrical wonders would
have unfolded itself to his vision and what a harvest of results such a
reaper would have gathered in! From solids, Gilbert proceeds to examine
the behavior of liquids, and finds that they, too, are susceptible of
electrical influence. He notices that a piece of rubbed amber when
brought near a drop of water deforms it, drawing it out into a conical
shape. He even experiments with smoke, concluding that the small carbon
particles are attracted by an electrified body. Some years ago, Sir
Oliver Lodge, extending this observation, proposed to lay the poisonous
dust floating about in the atmosphere of lead works by means of large
electrostatic machines. He even hinted in his Royal Institution lecture
that they might be useful in dissipating mists and fogs, and recommended
that a trial be made on some of our ocean-steamers.
Gilbert next tries heat as an agent to produce electrification. He takes
a red-hot coal and finds that it has no effect on his electroscope; he
heats a mass of iron up to whiteness and finds that it, too, exerts no
electrical effect. He tries a flame, a candle, a burning torch, and
concludes that all bodies are attracted by electrics save those that are
afire or flaming, or extremely rarefied. He then reverses the
experiment, bringing near an excited body the flame of a lamp, and
ingenuously states that the body no longer attracts the pivoted needle.
He thus discovered the neutralizing effect of flames, and supplied us
with the readiest means that we have to-day for discharging
non-conductors.
He goes a step further; for we find him exposing some of his electrics
to the action of the sun's rays in order to see whether they acquired a
charge; but all his results were negative. He then concentrates the rays
of the sun by means of lenses, evidently expecting some electrical
effect; but finding none, concludes with a vein of pathos that the sun
imparts no power, but dissipates and spoils the electric effluvium.
Professor Righi has shown that a clean metallic plate acquires a
positive charge when exposed to the ultraviolet radiation from any
artificial source of light, but that it does not when exposed to solar
rays. The absence of electrical effects in the latter case is attributed
to the absorptive action of the atmosphere on the shorter waves of the
solar beam.
Of course Gilbert permits himself some speculation as to the nature of
the agent with which he was dealing. He thought of it, reasoned about
it, pursued it in every way; and came to the conclusion that it must be
something extremely tenuous indeed, but yet substantial, ponderable,
material. "As air is the effluvium of the earth," he says, "so
electrified bodies have an effluvium of their own, which they emit when
stimulated or excited"; and again: "It is probable that amber exhales
something peculiar that attracts the bodies themselves."
These views are quite in line with the electronic theory of electricity
in vogue to-day, which invests that elusive entity with an atomic
structure. It is held that the tiny particles or electrons that are shot
out from the cathode terminal of a vacuum tube with astounding velocity
are none other than particles of negative electricity, pure and simple.
They have mass and inertia, both of which properties are held to be
entirely electrical, though quite analogous to the mass and inertia of
ordinary, ponderable matter.
History shows that scientific theories have their periods of infancy,
maturity and decay. When they have served their purpose, like the
scaffolding of a building, they are removed from sight and stored away,
say, in a limbo of discarded philosophy, for use of the historian of
science or of the metaphysician writing on the nature of human
knowledge. Such was the fate of Gilbert's "effluvium" theory of
electricity, of the fluid theories of Dufay and Franklin, and the
ether-strain theory of recent years. "Each physical hypothesis," says
Prof. Fleming, "serves as a lamp to conduct us a certain stage in the
journey. It illumines a limited portion of the path, throwing light
before and behind for some distance; but it has to be discarded and
exchanged at intervals because it has become exhausted and because its
work is done."
It is a little surprising that the phenomenon of electrical repulsion
should have escaped the attention of one so skilled in experimentation
as Gilbert. Yet such was the case; and Gilbert even went so far as to
deny its very existence, saying, "Electrics attract objects of every
kind; they never repel." This error reminds one of Gilbert's own saying
that "Men of acute intelligence, without actual knowledge of facts, and
in the absence of experiment, easily slip and err." Just twenty-nine
years after Gilbert had penned this aphorism, there appeared in Ferrara
an extensive work on electric and magnetic philosophy, by the Jesuit
Cabeo, in which this electrical repulsion was recognized and described.
Having rubbed one of his electrics, Cabeo noticed that it attracted
grains of dust at first and afterward repelled them suddenly and
violently. In the case of threads, hairs or filaments of any kind, he
observed that they quivered a little before being flung away like
sawdust. This self-repelling property of electricity, described in the
year 1629, opened up a new field of inquiry, which was actively explored
by a number of brilliant electricians in England and on the Continent.
This was especially the case after the building of the first frictional
machine by Otto von Guericke in 1672. The burgomaster of Magdeburg had
already acquired European fame by the original and sensational
experiments on atmospheric pressure which he made in presence of the
Emperor and his nobles in solemn diet assembled (1651). Von Guericke
seems to have been of a mind with Gilbert concerning writers on natural
science who treat their subjects "esoterically, miracle-mongeringly,
abstrusely, reconditely, mystically"; for he affirms that "oratory,
elegance of diction or skill in disputation avails nothing in the field
of natural science."
Von Guericke's machine consisted of a ball of sulphur, with the hand of
the operator or assistant as rubber. Some years later, the sulphur ball
was replaced by Newton (some say Hauksbee) by a glass globe, which, in
turn, was exchanged for a glass cylinder by Gordon, a Scotch
Benedictine, who was Professor of natural philosophy in the University
of Erfurt. In 1755, Martin de Planta, of Sus, in Switzerland,
constructed a plate-machine which was subsequently improved by Ramsden
of London. The frictional machine, as it was rightly called, has been
superseded by the influence machine, a type of static generator which is
at once efficient, reliable and easy of operation. The best known form
for laboratory use is that of Wimshurst (1832-1903), of London.
Andrew Gordon, the Scotch Benedictine to whom reference has just been
made, was a man of an inventive turn of mind. Besides, the cylindrical
electric machine which he constructed, he devised several ingenious
pieces of electrical apparatus, among which are the _electric chimes_
usually ascribed to Franklin. They are fully described in his _Versuch
einer Erklärung der Electricität_, published in 1745. On page 38, he
says that he was led to try an electrical method of ringing bells; and
then adds: "For this purpose I placed two small wine-glasses near each
other, one of which stood on an electrified board, while the other,
placed at a distance of an inch from it, was connected with the ground.
Between the two, I suspended a little clapper by a silk thread, which
clapper was attracted by the electrified glass and then repelled to the
grounded one, giving rise to a sound as it struck each glass. As the
clapper adhered somewhat to the glasses, the effect on the whole was not
agreeable. I, therefore, substituted two small metallic gongs suspended
one from an electrified conductor and the other from a grounded rod, the
gongs being on the same level and one inch apart. When the clapper was
lowered and adjusted, it moved at once to the electrified bell, from
which it was driven over to the other, and kept on moving to and fro,
striking the bell each time with pleasing effect until the electrified
bell lost its charge." In the illustration, _a_ is connected with the
electrified conductor; _b_ is the insulated clapper; _c_ the grounded
gong.
[Illustration: FIG. 10 Gordon's electric chimes, 1745]
Gordon's book was published in Erfurt in 1745, while the year 1752 is
that in which Franklin applied the chimes to his experimental rod to
apprise him of the approach of an electric storm, an application which
was original and quite in keeping with the practical turn of mind that
characterized our journeyman-printer, philosopher and statesman.
Unquestionably, Franklin had all the ingenuity and constructive ability
needed to make such an appliance; but there is no evidence that he
actually invented it. Though Franklin neither claimed nor disclaimed the
chimes as his own, all his admirers would have preferred less reticence
on his part when the discoveries and inventions of contemporary workers
in the electrical field were concerned. He had attained sufficient
eminence to permit him to look appreciatingly and encouragingly on the
efforts of others.
Gordon also invented a toy electric motor in which rotation was effected
by the reaction of electrified air-particles escaping from a number of
sharp points. One of these motors consisted of a star of light rays cut
from a sheet of tin and pivoted at the center, with the ends of the rays
slightly bent aside and all in the same direction. When electrified,
Gordon noticed that the star required no extraneous help to set it in
motion. It was a self-starting electric-motor. In the dark, the points
were tipped with light, and as they revolved traced out a luminous
circle which "could neither be blown out nor decreased."
The reader will recognize in this description taken from Gordon's
_Versuch_, page 45, the _electric whirl_ of the lecture-table; Gordon's
name is never associated with it, but that of Hamilton (Hamilton's "fly"
or Hamilton's "mill") sometimes is!
This irrepressible monk seems to have been one of the earliest
electrocutors, for it is said that many an innocent chaffinch fell
victim to discharges from his machine; and we would be disposed to think
of him as a wizard on learning that he ignited spirits by using an
electrified stream of water, to the astonishment and mystification of
the spectators.
Abbé Menon was kinder to the feathered tribe than his black-cowled
brother of Erfurt; he did not subject them to a powerful discharge, but
rather to a gentle electrification for the purpose of determining what
physical or physiological effect the agent would have on the animal
system. The Abbé found that cats, pigeons, sparrows and chaffinches lost
weight by being electrified for five or six hours at a time, from which
he concluded that electricity augments the slow, continuous perspiration
of animals. The same was found to take place with the human body itself.
The reader will remember that Stephen Gray in 1730 suspended a boy by
means of silken cords for the purpose of electrification; Abbé Nollet
did the same, and doubtless his friend Abbé Menon adopted a similar mode
of insulation for complacent electrical subjects. An easier mode of
operating would have been to make the child stand on a cake of resin,
the insulating property of which had been discovered by Stephen Gray.
About this time, 1746, Franklin appears on the scene, and though he
devoted but nine years (1746-1755) of his life to the study of
electricity, he made discoveries in that fascinating branch of human
knowledge that will hand his name down the centuries.
Franklin's life is interesting and instructive on account of the
difficulties which he met and overcame, for his strength of will,
tenacity of purpose, the philosophy which he followed, his devotedness
to science, and the success which he achieved.
Our philosopher's moral code comprised the thirteen virtues of
temperance, silence, order, resolution, frugality, industry, sincerity,
justice, moderation, cleanliness, tranquility, chastity and humility. To
each of these virtues Franklin attached a precept which makes edifying
reading even at the present day: _temperance_, eat not to dullness,
drink not to elation; _silence_, speak not but what may benefit others
or yourself, avoid trifling conversation; _order_, let all your things
have their places, let each part of your business have its time;
_resolution_, resolve to perform what you ought, perform without fail
what you resolve; _frugality_, make no expense, but do good to others or
yourself, _i.e._, waste nothing; _industry_, lose no time, be always
employed in something useful, cut off all unnecessary actions;
_sincerity_, use no hurtful deceit, think innocently and justly, and if
you speak, speak accordingly; _justice_, wrong no one by doing injury or
omitting the benefits that are your duty; _moderation_, avoid extremes,
forbear resenting injuries so much as you think they deserve;
_cleanliness_, tolerate no uncleanliness in body, clothes or habitation;
_tranquility_, be not disturbed by trifles or accidents common or
unavoidable; _chastity_ (no remark); _humility_, imitate Jesus.
This last virtue seems to have given Franklin very much concern; for he
admits that he had the appearance of humility, and immediately adds that
in reality there is no passion of the human breast so hard to subdue as
pride. He is shrewd enough to say that "even if I could conceive that I
had completely overcome it, I should probably be proud of my humility."
Like many another, the virtue which gave him the most trouble was
_order_, and this never became conspicuously apparent at any time of his
long life.
In his endeavors after the higher life, he seems to have been animated
with the earnest spirit of the ascetic who binds himself to strive after
perfection as laid down in the maxims and counsels of the Gospel. It is
not without surprise and perhaps a feeling too of self-condemnation,
that we read the means which he adopted to reach a high moral standard.
Taking for granted that he had a true appreciation of right and wrong,
he did not see why he should not always act according to the dictates of
conscience. To improve himself morally and advance in the higher life,
he adopted a means that should have proved effective. Taking the first
of the thirteen fundamental virtues, he applied himself to its
acquisition for a whole week together, after which he took the second,
then the third, and so on with the rest. He thought that by making daily
acts of the virtue, it would become habitual with him at the end of the
week. When the last of the thirteen virtues had received its share of
attention, he returned to the first one on the list and proceeded round
the cycle again. Being a man of purpose and tenacity, he completed the
circle of his chosen virtues four times a year; subsequently he extended
the time of individual practise so as to take a whole year for the
course; and later on, he devoted several years to the completion of his
list.
As an aid in this work of self-betterment, Franklin examined himself
daily, registering his failures in a little book which was ruled for
the purpose, a column being allowed for each day and a line for each of
the thirteen virtues. He naively tells us the result of this exercise of
daily introspection in these words: "I am surprised to find myself so
much fuller of faults than I had imagined; but I had the satisfaction of
seeing them diminish."
The evening examination of conscience was always concluded by the
following prayer written by Franklin himself: "O powerful Goodness!
bountiful Father! merciful Guide! increase in me that wisdom which
discovers my truest interest. Strengthen my resolutions to perform what
that wisdom dictates. Accept my kind offices to Thy other children as
the only return in my power for Thy continual favors to me."
An extensive reader, Franklin found in Thomson's poems some lines that
appealed to him very strongly by the beauty of the sentiment expressed.
He called them "a little prayer," which he recited from time to time:
"Father of light and life, Thou Lord Supreme,
Oh, teach me what is good; teach me Thyself.
Save me from folly, vanity and vice;
From every low pursuit; and fill my soul
With knowledge, conscious peace and virtue pure;
Sacred, substantial, never-failing bliss!"
His was a praiseworthy attempt at emancipating himself from the thraldom
of passion and raising himself to the high plane of perfection required
by the Master when He said "Follow Me." Doubtless, as time wore on, he
must have felt as many before and since, that the spirit is willing but
the flesh is weak.
In his autobiography, Franklin attributes his success in business not
only to his self-control, uniformity of conduct, philosophical
indifference to slight or pique, but also to his habits of frugality,
the result in part of his early training. "My original habits of
frugality continuing," he says, "and my father having frequently
repeated a proverb of Solomon, 'Seest thou a man diligent in his
business? he shall stand before kings,' I from thence considered
industry as a means of obtaining wealth and distinction, which
encouraged me, tho' I did not think that I should ever literally _stand
before kings_, which, however, has since happened." Our aged philosopher
proceeds to tell us of his good fortune with a little bit of pardonable
vanity, to which, by the way, he was never a great stranger, despite his
philosophy, acquired virtue, and staid character. Referring to the kings
of the earth, he informs us that he "_stood_ before five, and even had
the honor of _sitting down_ with one to dinner."
An important event in Franklin's life was the founding by him of the
first public library in the country in the year 1732. Though but
twenty-six years of age, he seems to have been as well aware as any of
the millionaire philanthropists of to-day, of the good that may be
accomplished among common people by providing them with suitable reading
matter. He watched with eagerness the progress of his experiment and was
pleased with the success that crowned it. He observes that such
libraries "tend to improve the conversation of Americans and to make
common tradesmen and farmers as intelligent (well-informed?) as most
gentlemen from other countries."
Peter Collinson, Fellow of the Royal Society of London, who had
dealings with some Philadelphia merchants, was led to take an active
interest in the library. This he did by sending over a number of books
and papers relating to electricity together with an "electrical tube"
with instructions for its use.
These literary and scientific contributions sent from London from time
to time, excited much interest among the charter members of the Library
Company, and principally that of Franklin himself. He had heard
something of the new order of phenomena which was just then engaging the
attention of European physicists. In the summer of 1746, while on a
visit to Boston, his native place, he assisted at a lecture on
electricity by a certain Dr. Spence, a Scotchman, who sought to
illustrate the properties of electrified bodies by such experiments as
could be made with glass tubes and suitable rubbers, the rudimentary
apparatus available at the time. Franklin was impressed by what he saw
and heard, even though he indulged in a little destructive criticism
when he said that the experiments were "imperfectly made," because the
lecturer was "not very expert." When Franklin wrote those words, he knew
by repeated and painful experience the difficulty of getting
satisfactory results from rubbing glass tubes or rotating glass globes,
owing to the provoking attraction which plain, untreated glass has for
moisture. Knowing this, he might have been less severe in his strictures
on his friend, the peripatetic electrician.
It is evident, however, that the experiments which he witnessed
surprised and pleased him, for, having shortly afterward received some
electrical tubes together with a paper of instructions, from his London
friend, Peter Collinson, he set to work for himself without delay. We
may well say of him that what his right hand found to do, he did
calmly, but with all his might. A twelve-month had not elapsed before he
wrote: "I never was engaged in any study that so totally engrossed my
attention and time as this has lately done; for, what with making
experiments when I can be alone and repeating them to my friends and
acquaintance who, from the novelty of the thing, come continually in
crowds to see them, I have had little leisure for anything else."
(1747.)
Here we see the calm, persistent character of the philosopher united
with the affability and communicativeness of the gentleman.
For the sake of encouraging others as well, perhaps, as through a sense
of personal relief, Franklin had a number of long tubes of large bore
blown at the local glass-house, which tubes he distributed to his
friends that they, too, might engage in research work. In this way,
rubbing and rubbing of an energetic kind became quite an occupation in
the Franklin circle. Kinnersley, whose name still survives in works on
static electricity in connection with an electric "thermometer" which he
devised, was among the band of ardent workers who ungrudgingly
acknowledged Franklin's superior acumen, comprehensive grasp of detail
and wondrous insight into the mechanism of the new phenomena. If we say
that Franklin was not a genius, it is only for the purpose of adding
that even in those early electrical studies he displayed an uncommon
amount of the unlimited capacity for taking pains which is said to be
associated with that brilliant gift. He tested all his results with
great care and in a variety of ways before accepting any of them as
final; and considered his explanations of them provisional, being ever
ready to modify them or give them up altogether if shown to conflict
with the simple workings of nature.
As early as 1733, the refined and tactful Dufay, in France, showed by
numerous experiments on woods, stones, books, oranges and metals that
all solid bodies were susceptible of electrification. This was a notable
advance which swept away Gilbert's classification of bodies into
electrics and non-electrics. The French physicist soon drew from his
observations the conclusion that electrification produced by friction is
of two kinds, to which he applied the terms vitreous and resinous, the
former being developed when glass is rubbed with silk and the latter
when amber or common sealing-wax is rubbed with flannel. He noticed,
too, that silk strings repelled each other when both were touched either
with excited glass or sealing-wax; but that they attracted each other
when touched one with glass and the other with sealing-wax. From these
observations, he deduced the electrostatic laws, that similarly
electrified bodies attract while dissimilarly electrified bodies repel
each other.
The law of distance was discovered later by Coulomb, who, in 1785,
showed that the law of repulsion as well as of attraction between two
electrified particles varies inversely as the square of the distance. In
the year 1750, the law of the inverse square for magnets was stated by
John Michell, who expressed it by saying that the "attraction and
repulsion decrease as the square of the distance from the respective
poles increases." Michell was fourth wrangler of his year (1748-9),
Fellow of Queen's College, Cambridge, and inventor of the _torsion
balance_, which, however, he did not live to use; but which, in the
hands of Cavendish, yielded important results on the mean density of
the earth. Coulomb probably re-invented the "balance" and applied the
practical, laboratory instrument which he made it, to the study of the
quantitative laws of electricity and magnetism.
To observe and correlate phenomena is the special work of the physicist;
to speculate on ultimate causes is the privilege of the philosopher.
Dufay was both. The theory which he offered was a simple one, even if
untrue to nature. It was a good working hypothesis for the time being.
According to this theory, there are two distinct, independent electrical
fluids mutually attractive but self-repelling. With that postulate,
Dufay was able to offer a plausible explanation of a great many
phenomena that puzzled the electricians of the time.
Franklin, however, held a different view; rejecting the dual nature of
electricity, he propounded his one-fluid theory, which was found equally
capable of explaining electrical phenomena. A body having an excess of
the fluid was said to be _positively_ charged, while one with a deficit
was said to be _negatively_ charged. The sign plus was used in one case
and the sign minus in the other; and just as two algebraical quantities
of equal magnitude but opposite sign give zero when added together, so a
conductor to which equal quantities of positive and negative electricity
would be given would be in the neutral state. The Franklinian theory was
welcomed in England, Germany and Italy, but it met with opposition in
France from the brilliant Abbé Nollet and the followers of Dufay.
Each of the rival theories affords a mental conception of the forces in
play and also a consistent explanation of the resulting phenomena. Their
simplicity, and, at the same time, the comprehensiveness of explanation
which they afford, will continue to give them a place in our text-books
for many years to come.
Efforts are being made to apply the _electronic_ theory to the various
phenomena of electrostatics, the electron being the smallest particle of
electricity that can have separate, individual existence. It is many
times smaller than the hydrogen atom, the smallest of chemical atoms,
and it possesses all the properties of negative electricity. By the loss
of one or more electrons, a body becomes positively electrified, whereas
by the acquisition of one or more electrons it becomes negatively
electrified. The electron at rest gives rise to the phenomena of
electrostatics; in motion, it gives rise to electrical currents,
electromagnetism and electric radiation.
We do not know what led Franklin to call positive the electrification of
glass when rubbed with silk, and negative that of sealing-wax when
rubbed with flannel. If he meant to imply that positive is the more
important of the two, he erred, for many reasons can be given to show
the preponderating influence of negative electricity; but it is too late
now to change the terminology.
If asked to point out differences between the physical effects of
positive and negative electrification, we would refer to the positive
brush, which is finer and much more developed than the negative; to the
Wimshurst machine, with its positive brushes on one side and negative
"beads" on the other; to the positive charge acquired by a clean plate
of zinc when exposed to ultraviolet light; to the ordinary vacuum tube
in which there is a violet glow at the cathode end or negative terminal;
to Crookes's tubes, X-ray tubes and other high vacuum tubes, in which
electrified particles, Kelvin's _molecular torrent_, are shot out from
the negative electrode with great velocity; and to arc-lamps using a
direct current in which the plus carbon is hollowed out crater-like, has
the higher temperature and wastes away twice as fast as the negative.
The year 1746 is an _annus mirabilis_ in the history of electricity, for
it was in the January of that year that an attempt to electrify water by
Musschenbroek, of Leyden, led to the discovery of the principle of the
electrostatic condenser. Whatever may be thought of the claim for
priority put forward in favor of Dean von Kleist, of Cammin in
Pomerania, or of Cunæus, of Leyden, it is certain that the discovery
became known throughout Europe by the startling announcement and
sensational description given of it by Musschenbroek, a renowned
professor of a renowned university. He was not only surprised but
terror-stricken by the effect of the electric energy which he had
unconsciously stored up in his little phial; for after telling his
French friend Réaumur, the physicist, that he felt the commotion in his
arms, shoulders and chest, he added that he would not take another shock
for the whole kingdom of France! A resolution destined to be broken,
like so many others before and since.
[Illustration: FIG. 11 Modern form of Leyden jar with movable coatings]
Very different was the sentiment of Bose, Professor of Physics in the
University of Wittenberg, who is credited with saying that he would like
to die by the electric shock, that he might live in the memoirs of the
French Academy of Sciences.
The Leyden jar became at once the scientific curiosity and universal
topic of discussion of the time; and not only was it the curiosity, but
also the _crux_ of the day, puzzling investigators, perplexing
philosophers and giving rise to animated controversies. The mystery was
soon dispelled, however, when Franklin began in 1747 his searching
inquiry into the electric conditions of each element of the jar. Nothing
escaped his subtle mind and nothing was left undone by his deft hand.
The evidence of experiment and the logic of facts carried at last
conviction even with Londoners and Parisians, who were wont to look upon
Americans as mere colonists, who had neither time nor opportunity for
scientific pursuits, being obliged to hew their way through virgin
forests or drive the roving Indian back from their frontiers into the
wilds of the West. The theory of the Leyden jar given by Franklin 160
years ago has stood the test of time. It has met with universal
acceptance; and, despite our manifold advances, but little of permanent
value has been added to it.
It is very interesting to follow the main lines of this magnificent
research. Franklin electrifies, in the usual way, water contained in a
small flask, complaisantly taking the shock on completing the circuit.
To find where the charge resides, whether in the hand of the operator,
as some said, or in the water, as others maintained, he again
electrifies the water and pours it into another flask, which fails,
however, to give a shock, thus showing that the charge had not been
carried over with the water. Convinced that the charge was still
somewhere in the first phial, he carefully poured water into it again;
and found, to his intense satisfaction, that it was capable of giving an
excellent shock. It was now clear to him that the energy of the charge
was either in the hand of the experimenter or in the glass itself, or in
both. To determine this nice point, he proceeds to construct a "jar"
which could easily be taken to pieces. For this purpose, he selected a
pane of glass; and, laying it on the extended hand, placed a sheet of
lead on its upper surface. The leaden plate was then electrified; and
when touched with the finger, a spark was seen and a shock felt. By the
addition of another plate to the lower surface, the shocking power of
this simple condenser was increased. In this efficient form he had a
readily dissectible condenser, which allowed him to throw off and
replace the coatings at will, and thereby to prove beyond cavil that the
seat of the stored-up electric energy is not in the conductors, but in
the glass itself. This was a discovery of the first magnitude and one
destined to associate the name of Franklin with those of the most
eminent electricians down the ages. Fig. 11 shows the modern form of the
jar with movable coatings.
[Illustration: FIG. 12 Three coated panes in _series_]
[Illustration: FIG. 13 Three panes in _parallel_]
In the "fulminating" pane, as it came to be called, we have one of the
eleven elements of Franklin's historic battery of 1748. It is
interesting to notice that he was accustomed to connect his "panes" in
series while charging (Fig. 12), but that he preferred to join similar
coatings together, that is, to couple them in "parallel" (Fig. 13), for
powerful discharges. Fig. 14 shows three jars in "parallel."
Later on, he arranged Leyden jars so that the inside coating of one
could be hooked to the outside coating of another, the first of the
series hanging down from the prime conductor of the machine, while the
last one was grounded. "What is driven out of the tail of the first," he
quaintly says, "serves to charge the second; what is driven out of the
second serves to charge the third, and so on." This has become known as
the "cascade" method of charging a battery, owing to the flow of
electricity from one jar to the next (Fig. 15). Electricians, however,
have discarded the picturesque "cascade" for the prosaic term of
"series" or "tandem" arrangement.
[Illustration: FIG. 14 Three jars in _parallel_]
[Illustration: FIG. 15 Three jars in _cascade_]
Franklin also noticed that a phial cannot be charged while standing on
wax or on glass, or even while hanging from the prime conductor, unless
communication be formed between its outer coating and the floor, the
reason given being that "the jar will not suffer a charging unless as
much fire can go out of it one way as is thrown in by the other."
(1748.)
Following his very ingenious Philadelphia friend and co-worker,
Kinnersley, he varies the mode of charging by electrifying the outside
of the jar and grounding the inner coating; for "the phial will be
electrified as strongly if held by the hook and the coating applied to
the globe as when held by the coating and the hook applied to the
globe." (1748.)
The globe here referred to is the glass globe of Franklin's frictional
machine of American make, which, when rotated, was electrified
positively by contact with the hand or with a leather rubber. Franklin
also used a sulphur ball or "brimstone" globe, and observed that the
electrification produced on it differed in kind from that developed on
the glass globe. (1752.)
It may here be stated that the first to use a _leather cushion_ as a
substitute for the hand in the frictional machine, was Winkler, of
Leipzig (1745); the efficiency of the rubber was increased by Canton, of
London, who covered it with an _amalgam_ of tin and mercury (1762).
Bose, of Wittenberg, had previously added the _prime-conductor_, which
greatly augmented the electrical capacity and output of the machine.
In 1750 Franklin imitated the effect of lightning on the compasses of a
ship by the action of a jar discharge on an unmagnetized steel needle.
"By electricity," he says, "we have frequently given polarity to needles
and reversed it at pleasure."
Similar experiments are made to-day in every lecture-course on static
electricity; but the experimenter, when wise, does not announce
beforehand which end of the needle will be north and which south, as he
is just as likely to be wrong as right, the uncertainty being due to the
fact that the discharge of a Leyden jar is not a current of electricity
in one direction, but rather a few sudden rushes or rapid surgings of
electricity to and fro; in other words, it is oscillatory in character
instead of being continuous in one direction.
Franklin did not know this; although he made a very pertinent remark in
1749 when he likened the mechanical condition of the glass of a charged
jar to that of a bent rod or a stretched spring. "So, a straight
spring," he says, "when forcibly bent must, to restore itself, contract
that side which in the bending was extended, and extend that side which
was contracted." Franklin knew, of course, that the bent rod, when
released, would swing to and fro a few times before settling down to its
state of rest; but he failed to see the analogy between it and the
strained glass of the charged Leyden jar.
It is to Joseph Henry (1799-1878), the Faraday of America, that we owe
the recognition and statement of the oscillatory character of the
discharge from Leyden jars and condensers generally. He discovered and
published this cardinal fact in 1842. His words deserve recording. "The
discharge, whatever may be its nature, is not correctly represented
(employing for simplicity the theory of Franklin) by the single transfer
of an imponderable fluid from one side of the jar to the other; the
phenomenon requires us to admit _the existence of a principal discharge
in one direction and then several reflex actions backward and forward,
each more feeble than the preceding, until equilibrium is
attained._"[10] The italics are Prof. Henry's.
It is precisely this oscillatory character of the spark-discharge that
enables us to send out trains of electric waves into the all-pervading
ether, and thus to communicate, by "wireless," with remote stations.
Having conclusively proved that the energy of a charged condenser
resides in the dielectric, Franklin next tries to find whether "the
electric matter" in the case of conductors is limited to the surface or
whether it penetrates to an appreciable depth. To ascertain this, he
insulates a silver fruit-can and brings a charged ball, held by a silk
thread, into contact with the outer surface. On testing after removal,
he found that the ball retained some of its charge, whilst it lost all
if allowed to touch the bottom of the vessel. Surprised at this
unexpected difference, he repeated the experiment again and again, only
to find the ball every time without a trace of charge after contact with
the interior of the vessel. This perplexed and puzzled him. "The fact is
singular," he says, "and you require the reason? I do not know it. I
find a frank acknowledgment of one's ignorance is not only the easiest
way to get rid of a difficulty, but the likeliest way to obtain
information, and therefore I practice it. I think it an honest policy.
Those who affect to be thought to know everything, often remain long
ignorant of many things that others could and would instruct them in, if
they appeared less conceited."
This was in 1755. Cavendish in 1773 and Coulomb in 1788 independently
attacked the same problem; and having proved by their classic
experiments that a static charge is limited to the surface of
conductors, it was but a step to infer that such a distribution of
electricity implies that the law of force between two elements of
charge, or between two point-charges, is the law of the inverse square
of the distance.
It will also be remembered that Faraday, not knowing what had been
accomplished eighty years before in Philadelphia, used for one of his
best-known experiments an ice-pail, into which he lowered an electrified
ball for the purpose of showing the exact equality of the induced and
the inducing charge. The similarity of apparatus and mode of procedure
are remarkable.
In pursuing his work, Franklin placed a charged jar on a cake of wax and
other insulating materials, and drew sparks from it by touching
successively the knob and the outer coating, repeating the process a
great number of times to his infinite delight. He next attached a brass
rod to the outside, bending it and bringing the other end close to the
knob (Fig. 16) connected with the inner coating. Between these two he
suspended a leaden ball by a silk thread and found, as he expected, that
it played to and fro between the terminals for a considerable time.
Observe that we have here a definite mass maintained in a state of
reciprocating motion by a series of electric attractions and repulsions.
We have in fact an electro-motor, closely resembling the star and the
chimes of Gordon, the Benedictine, 1745; a mere toy, if you will, but
still a remarkable invention. We repeat the same experiment to-day only
with a little more harmony, by substituting for the knobs two little
bells, which emit a soft, musical note when struck by the interhanging
clapper.
[Illustration: FIG. 16 Discharge by alternate contacts]
This experiment has further significance, for, like Gordon's chimes, it
is an instance of the conveyance of electricity from one point of space
to another by means of a material carrier, a mode of transfer which has
since been called "electric convection," the full meaning of which was
not revealed until Rowland (1848-1901), made his famous experiment of
1876 in the laboratory of the University of Berlin with a
highly-charged, rapidly-revolving, ebonite disc. It was apropos of this
experiment that the illustrious Clerk Maxwell, of the University of
Cambridge, wrote to his friend, Professor Tait, of Edinburgh, saying
that:
"The mounted disc of ebonite
Had whirled before, but whirled in vain;
Rowland of Troy, that doughty knight,
Convection currents did obtain,
In such a disc, of power to wheedle
From its loved north, the needle."
We may here say that Franklin was no stranger to the work done by the
electrical pioneers of the Old World, his diligent London friend, Peter
Collinson, keeping him advised by means of letters, books and pamphlets,
in which inspiration and practical hints must have been found. He
certainly was well acquainted with the achievements of Dr. Watson and
Dr. Bevis, of London, as well as with the theories and experiments of
Dufay and Abbé Nollet in Paris. It is germane to the subject to say that
Dr. Bevis used mercury and iron filings for the inner coating of his
jars, as well as sheet lead for both. He also experimented with coated
panes of glass instead of jars. About this, Franklin wrote to Collinson:
"I perceive by the ingenious Mr. Watson's last book, lately received,
that Dr. Bevis had used, before we had, panes of glass to give a shock;
though till that book came to hand, I thought to have communicated it to
you as a novelty." (1748.)
Franklin gave way to a little pleasant humor when, in 1748, he proposed
to wind up the "electrical season" by a banquet à la Lucullus, to be
given to a few of his friends and fellow-workers, not in a sumptuously
decorated hall, but _al fresco_, on the banks of the Schuylkill. "A
turkey is to be killed for our dinner by the electrical shock," he
wrote, "and roasted by the electrical jack before a fire kindled by the
electrical bottle, when the healths of all the famous electricians in
England, Holland, France and Germany are to be drunk in electrified
bumpers under the discharge of guns fired from the electrical battery."
It is hardly to be supposed that such an elaborate program was carried
out. Indeed the difficulty of preparing the apparatus and getting it
ready for action on the banks of a river were formidable enough to say
the least. Franklin, however, had a Leyden battery capable of doing
considerable electrocution, for with two jars of six gallons capacity
each, he knocked six men to the ground; the same two jars sufficed to
kill a hen outright, whereas it required five, he tells us, to kill a
turkey weighing ten pounds.
The "electrical bumper" was a wine-glass containing an allowance, let us
say, of some favorite brand and charged in the usual way. On approaching
the lips the two coatings would be brought within striking-distance and
a spark would take place, if not to the delight of the performer, at
least to the amusement of the on-lookers. It was subsequently remarked
that guests whose upper lip was adorned with a moustache could quaff the
nectar with impunity, as every bristle would play the part of a filiform
lightning-rod and prevent the apprehended, disruptive discharge!
Not quite so humorous was his suggestion of a hammock to be used by
timid people during an electric storm: "A hammock or swinging-bed,
suspended by silk cords equally distant from the walls on every side,
and from the ceiling and floor above and below, affords the safest
situation a person can have in any room whatever; and which, indeed, may
be deemed quite free from danger of any stroke of lightning." (1767.)
In his experiments on puncturing bodies by the spark-discharge, Franklin
does not fail to notice the double burr produced when paper is used.[9]
His words are:
"When a hole is struck through pasteboard by the electrified jar, if the
surfaces of the pasteboard are not confined or compressed, there will be
a bur raised all round the hole on both sides the pasteboard, for the
bur round the outside of the hole is the effect of the explosion every
way from the centre of the stream and not an effect of direction."
(1753.) The spelling is Franklin's _unreformed_.
The to-and-fro nature of the discharge was thought, at a time, to
account satisfactorily for the burr raised on each side of the
pasteboard; but Trowbridge, of Harvard, has shown that even a
unidirectional discharge, such as can be obtained by inserting a wet
string or any high resistance in the circuit, would produce a double
burr, from which we infer, confirming Franklin, that this effect of the
discharge is caused by the sudden expansion of air within the paper
itself.
By the year 1749, Franklin had reached the conclusion that the lightning
of the skies is identical with that of our laboratories, basing his
belief on the following analogies which he enumerates in the notes or
"minutes" which he kept of his experiments: "The electric fluid agrees
with lightning in these particulars: (1) Giving light; (2) color of the
light; (3) crooked direction; (4) swift motion; (5) being conducted by
metals; (6) crack or noise in exploding; (7) rending bodies it passes
through; (8) destroying animals; (9) melting metals; (10) firing
inflammable substances; and (11) sulphurous smell."
But although he felt the full force of the analogical argument, Franklin
knew that the matter could not be finally settled without an appeal to
experiment; and accordingly he adds: "The electric fluid is attracted by
points; we do not know whether this property is in lightning. But since
they agree in all the particulars wherein we can already compare them,
is it not probable that they agree likewise in this? Let the experiment
be made." (1749.)
In writing to Collinson in July, 1750, he tells his London friend how
the experiment may be made: "On the top of some high tower or steeple,
place a kind of sentry-box--big enough to contain a man--and an
electrical stand. From the middle of the stand let an iron rod rise and
pass, bending out of the door, and then upright 20 or 30 feet, pointed
very sharp at the end. If the electrical stand be kept clean and dry, a
man standing on it, when such clouds are passing low, might be
electrified and afford sparks, the rod drawing fire to him from the
cloud."
Collinson brought some of Franklin's letters to the notice of
fellow-members of the Royal Society with a view to their insertion in
the _Philosophical Transactions_ of that learned body; but even his
epoch-making letter to Dr. Mitchell, of London, on the identity of
lightning and electricity, was dismissed with derisive laughter. The
Royal Society made amends in due time for their contemptuous treatment
of the American philosopher by electing him member of the Society and by
awarding him the Copley medal in 1753.
Disappointed as he was, Collinson collected Franklin's letters and
published them under the title of _New Experiments and Observations on
Electricity made at Philadelphia in America_. The pamphlet appeared in
1751, and was immediately translated into French by M. d'Alibard at the
request of the great naturalist Count de Buffon.
The experiments described in the pamphlet, and especially that of the
pointed conductor, were taken up in Paris with great enthusiasm by de
Buffon himself, by d'Alibard, a botanist of distinction, and by de Lor,
a professor of physics. Following out the instructions given by
Franklin, they were all able to report success: d'Alibard on May 10th,
de Lor on May 18th, and de Buffon on May 19th, 1752.
De Buffon erected his rod on the tower of his château at Montbar; de
Lor, over his house in Paris, and d'Alibard, at his country seat at
Marly, a little town eighteen miles from Paris. D'Alibard was not at
home on the eventful afternoon of May 10th; but before leaving Marly, he
had drilled a certain Coiffier in what he should do in case an electric
storm came on during his absence. Though a hardy and resolute old
soldier and proud of the confidence placed in him, Coiffier grew alarmed
at the long and noisy discharges which he drew from the _insulated_ rod
on the afternoon of May 10th. While the storm was still at its height he
sent for the Prior of the place, Raulet by name, who hastened to the
spot, followed by many of his parishioners. After witnessing a number of
brilliant and stunning discharges, the priest drew up an account of the
incident and sent it, at once, by Coiffier himself to d'Alibard, who was
then in Paris. Without delay d'Alibard prepared a memoir on the subject
which he communicated to the Académie des Sciences three days later,
viz.: on May 13th. In the concluding paragraph, the polished academician
pays a graceful tribute to the philosopher of the Western World:
"It follows from all the experiments and observations contained in the
present paper, and more especially from the recent experiment at
Marly-la-ville, that the matter of lightning is, beyond doubt, the same
as that of electricity; it has become a reality, and I believe that the
more we realize what he (Franklin) has published on electricity, the
more will we acknowledge the great debt which physical science owes
him."
We may, in passing, correct the error of those who credit French
physicists with having originated the idea of the pointed conductor.
Such writers should read the words of d'Alibard in the beginning of his
memoir, where he says: "En suivant la route que M. Franklin nous a
tracée, j'ai obtenu une satisfaction complète"; that is, "In following
the way traced out by Franklin, I have met with complete success." To
Franklin, therefore, belongs the idea of the pointed rod of 1750, which
became the lightning conductor of subsequent years; to the Parisian
savants belongs the great distinction of having been the first to make
the experiment and verify the Franklinian view of the identity of the
lightning of our skies with the electricity of our laboratories.
Franklin had precise ideas on the action of his pointed conductors,
clearly recognizing their twofold function: (1) that of preventing a
dangerous rise of potential by disarming the cloud; and (2) that of
conveying the discharge to earth, if struck. In some of his letters, he
complains of people who concentrate their attention on the preventive
function, forgetting the other entirely. "Wherever my opinion is
examined in Europe," he wrote in 1755, "nothing is considered but the
probability of these rods preventing a stroke, which is only a part of
the use I proposed for them; and the other part, their conducting a
stroke which they may happen not to prevent, seems to be totally
forgotten, though of equal importance and advantage."
A favorite illustration of Franklin's showing the discharging power of
points, consisted in insulating a cannon ball against which rested a
pellet of cork, hung by a silk thread. On electrifying the ball, the
cork flies off and remains suspended at a distance, falling back at
once, as soon as a needle is brought near the ball. (1747.)
He also used tassels consisting of fifteen or twenty long threads (Fig.
17), and even cotton-fleece, the filaments of which stand out when
electrified, but come together when a pointed rod is held underneath. He
also noticed that the filaments do not collapse when the point of the
rod is covered with a small ball. (1762.)
[Illustration: FIG. 17 Tassel of long threads or light strips of paper]
Franklin's views on lightning-rods met with some opposition in France
from the brilliant Abbé Nollet, and in England from Dr. Benjamin Wilson.
The latter was mainly instrumental in bringing about the famous
controversy of "Points _vs._ Knobs." In 1772, a committee was appointed
by the Royal Society to consider the best means of protecting the
powder-magazines at Purfleet from lightning. On the committee with Dr.
Wilson were Henry Cavendish, the distinguished chemist and physicist,
and Sir John Pringle, President of the Royal Society. The report favored
sharp conductors against blunt ones advocated by Dr. Wilson. Five years
later, in 1777, the question was again brought up, and again the new
committee decided in favor of pointed terminals, convinced "that the
experiments and reasons made and alleged to the contrary by Mr. Wilson
were inconclusive."
Dr. Wilson, being a man of influence, succeeded in having his views
taken up by the Board of Ordnance. It has been remarked that this
controversy would never have attracted attention but for the fact that
the discoverer of the effect of points was Franklin. He was an American
and the dispute with the colonies was then at its height. The war of the
Revolution had begun, and the British forces had already met with
serious reverses. No patriot could, therefore, admit any good in points.
George III. took sides, decreed that the points on the royal conductors
at Kew should be covered with balls, and ordered Sir John Pringle to
support Dr. Wilson. Sir John gave the dignified answer: "Sire, I cannot
reverse the laws and operations of nature"; to which the King, incensed
that so incompetent a man should hold such an important office, replied:
"Then, Sir John, perhaps you had better resign," which Sir John did.
A wit of the time put the matter epigrammatically when he wrote:
"While you, great George, for knowledge hunt
And sharp conductors change to blunt,
The nation's out of joint;
Franklin a wiser course pursues,
And all your thunder useless views
By keeping to the point."
It was in connection with this heated controversy that Franklin wrote
the following admirable words:
"I have never entered into any controversy in defence of my
philosophical opinions. I leave them to take their chance in the world.
If they are _right_, truth and experience will support them; if _wrong_,
they ought to be refuted and rejected. The King's changing his _pointed_
conductors for _blunt_ ones is, therefore, a matter of small importance
to me."
It was not until September, 1752, that Franklin raised a rod over his
own house. This experimental conductor was made of iron fitted with a
sharp steel point and rising seven or eight feet above the roof, the
other end being buried five feet in the ground. In order to avoid
useless personal displacement, Franklin, the economist of time, made an
automatic annunciator similar to that devised by Gordon in 1745, and
described by Watson in his _Sequel_, 1746, to apprize him of the advent
of a good thunder-gust. Instead of making the rod of one continuous
length, it was divided on the staircase, opposite his chamber door, the
ends being drawn apart to a horizontal distance of a few inches.
Screwing a pair of tiny gongs to the ends, he suspended between them a
brass ball, held by a silk thread, to act as clapper. Whenever a
thundercloud came hovering by, the bells began to ring, thereby
summoning the philosopher to his "laboratory" on the staircase.
Franklin's rod, erected over his house in the summer of 1752, was
evidently intended by him for experimental rather than protective
purposes. There is no doubt whatever in his mind about the use of such
pointed conductors for the protection of buildings and ships against the
destructive effects of lightning. He expressly says, in an article
printed in _Poor Richard's Almanack_ for 1753, that "It has pleased God
in His infinite goodness to mankind, to discover to them the means of
securing their habitations and other buildings from mischief by thunder
and lightning. The method is this: provide a small iron rod (it may be
made of the rod-iron used by the nailers), but of such a length, that
one end being 3 ft. or 4 ft. in the moist ground, the other may be 6 ft.
or 8 ft. above the highest part of the building. To the upper end of the
rod fasten about a foot of brass-wire, the size of a common knitting
needle, sharpened to a fine point; the rod may be secured to the house
by a few small staples. If the house or barn be long, there may be a rod
and point at each end, and a middling wire along the ridge from one to
the other. A house thus furnished will not be damaged by lightning, it
being attracted by the points and passing through the metal into the
ground without hurting anything. Vessels also, having a sharp-pointed
rod fixed on the top of their masts, with a wire from the foot of the
rod reaching down round one of the shrouds to the water, will not be
hurt by lightning."
It is well known, as Dr. Rotch, Director of the Blue Hill Observatory,
recently pointed out, that the matter for these almanacs was prepared by
Franklin himself under the pen-name of Richard Saunders. As the above
passage appeared in the almanac for 1753, it is obvious that it must
have been ready sometime toward the end of 1752. Furthermore, we know
that it was actually in the hands of the printer in the middle of
October of that year, for the _Pennsylvania Gazette_ of Oct. 19th says
that the almanac was then in press and that it would be on sale shortly.
Whence it follows that the year 1752 is the year of the invention of the
lightning rod, and not 1753 or 1754 as often stated.
The instructions given by Franklin include all the essentials necessary
for the erection of a lightning conductor. It may be made of iron or
copper, flat or round, but must make good "sky" and good "earth." The
former condition is secured by screwing to the top of the rod either
copper or platinum terminals ending in sharp points; and the latter, by
burying the lower end deep in moist soil. Between "sky" and "earth" the
rod must be continuous.
The function of the rod is twofold, as Franklin well recognized,
preventive and preservative. It prevents the stroke, under ordinary
conditions, by the action of the points, which send off copious streams
of air and dust particles electrified oppositely to that of the cloud.
Even at a distance, the dangerous potential of the cloud is reduced by
these convection currents and the stroke ordinarily averted. It is clear
that ten points are more efficacious than one, and fifty more than five.
Hence the number of points which we see distributed over the higher and
more conspicuous parts of a building, all of which are carefully
connected with the lightning conductor.
However well a building may theoretically be protected, conditions will
occasionally arise when the rod will inevitably be struck; its
preservative function then comes into play, by which it carries the
energy of the disruptive discharge safely to earth.
The experience of more than a century shows that the lightning-rod
affords protection in the great majority of cases; but it would be at
least a mild exaggeration to say that it never failed, even when
properly constructed.
At first, the erection of lightning-rods was opposed in the New World as
well as in the Old: some based their opposition to the novelty on
religious grounds, saying that, as lightning and thunder are tokens of
divine wrath, it would be impious to interfere in any way with their
manifestations. This objection was met by saying that for a parity of
reason we should avoid protecting ourselves against the inclemencies of
the weather.
Others opposed the use of the rods on the score that they invited or
attracted the flash, which was answered by saying that they attract
lightning as much as a rain-pipe attracts a shower, and no more.
The death of Professor Richmann, of the University of St. Petersburg,
also tended to retard the adoption of the rod for the protection of
buildings; but the invalidity of that objection became apparent when the
circumstances of the accident became known. Richmann's conductor was
like d'Alibard's (1751), an experimental rod, and as such was insulated
at the lower end. It was, therefore, not a lightning-rod at all,
inasmuch as it was not grounded. On August 6th, 1753, during a violent
electric storm, Richmann happened to be close to his exploring rod
observing the indications of a roughly-made electrometer, when a sharp
thunder-clap was heard, and at the same instant a ball of fire was seen
by Richmann's assistant to dart from the apparatus and strike the head
of the unfortunate Professor, who fell over on a near-by chest and
expired instantly. His assistant was stunned for a while. On regaining
consciousness, he ran to the aid of the Professor; but it was too late,
the body was lifeless.
In recording this tragic event, Priestley, the historian of electricity,
says that, "It is not given to every electrician to die in so glorious a
manner as the justly envied Richmann."
For one, we do not "envy" Professor Richmann's fate, and we think that
the phrase "tragic manner" would better suit the circumstances of his
death than the "glorious manner" of Dr. Priestley.
Risks of a similar character were taken by Franklin in Philadelphia, de
Romas in Bordeaux, and d'Alibard's representative at Marly, when
experimenting with kites and insulated rods; they took their lives in
their hands, though they may not have thought so.
A few years ago, Sir William Preece said that a man might with impunity
"clasp a copper rod an inch in diameter, the bottom of which is well
connected with moist earth, while the top of it receives a violent flash
of lightning; the conductor might even be surrounded by gunpowder in the
heaviest storm without risk or danger."
It is not on record that the English electrician ever clasped a
lightning conductor or even stood in close proximity to one during an
electric storm. The above statement was as sensational as it was unwise
and foolhardy. The neighborhood of a rod during a storm is a zone of
danger, owing to the electrical surgings which are set up in it, and, as
such, is to be avoided.
The death of Richmann caused quite a sensation throughout Europe, and
naturally the lightning-rod came in for severe condemnation. Among the
memoirs to which the fatality gave rise was one written in the heart of
Moravia and addressed to the celebrated Euler, Director of the Academy
of Sciences at Berlin. The writer was a monk of the Premonstratensian
Order, whose field of labor was at Prenditz.
In the year 1754, this country priest made experiments with lightning
conductors on a scale that transcended anything done in Paris, London or
Philadelphia. The accompanying illustrations show the conductor which
Divisch (also Diwisch) raised at Prenditz (also Brenditz) in the summer
of that year to demonstrate publicly the efficacy of such apparatus in
breaking up thunder-clouds and neutralizing the destructive energy pent
up in their electric charges. Prenditz, it would appear, suffered
severely from electric storms; and it was mainly for the safety of the
locality that the good priest devoted himself with earnestness to the
study of electrical phenomena.
As such a man deserves to live in the memory of posterity, we have
sought out the leading facts of his career mainly from Father Alphons
Zák, of Pernegg, in Lower Austria, a distinguished writer of the Order
to which Divisch belonged, and have woven such details as we obtained
from him and others into the simple narrative that follows.
[Illustration: FIG. 18 Procopius Divisch (1696-1765)]
Procopius Divisch (Prokop Diwisch) was born on Aug. 1st, 1696, at
Helkowitz-Senftenberg in Bohemia. He spent his youth at Znaim, where he
studied the humanities and philosophy at the College conducted by the
Jesuit fathers in that Moravian city. In 1719, when in his twenty-third
year, he decided to quit the common ways of the world in order to lead
the higher life in the Premonstratensian Order at Kloster-Bruck. At the
ripe age of 30, Divisch was ordained priest, in 1726, after which he
taught philosophy and theology to classes of young aspirants to the
ecclesiastical state. In 1733 he went to the University of Salzburg and
won his double Doctorate in theology and philosophy. Three years later,
in 1736, he was appointed parish priest of Prenditz, a small Moravian
town on the road to Austerlitz, since of Napoleonic fame. Here he
remained for five years, returning in 1741 to Bruck as Prior of the
Kloster or monastery situated there. At the end of the Seven Years' War
of the Austrian succession, he quitted Bruck, in 1745, for his parish at
Prenditz, where he spent the last twenty years of his life in the
pastoral ministrations of his sacred office and in electrical
experimentation, of which he was very fond.
The curative property of the new agent was heralded throughout Europe
about this time in terms of unmeasured praise. Some of Divisch's ailing
parishioners, believing him to be an expert in electrical manipulation,
applied to him for a little alleviation of their woes. The good-hearted
priest did not turn them away, but thought it desirable to treat them to
the therapeutic effect of such sparks as he could get from his homemade
frictional machine. The results were various, depending probably on the
confidence and imagination of the patient. Several remarkable cures
seem to have been effected either by the electric spark or by the
persuasive powers of the operator, or by both combined, with the result
that people far and wide were divided in their opinion of the Pastor of
Prenditz. Some physicians said that he was interfering with their
practice, and even clergymen found fault with him for indulging in work
which they thought unsuited to the cloth. A general impression, too,
seems to have prevailed that his electrical experiments, especially
those with his lightning conductor, were likely to prove harmful in more
ways than one.
On the other hand, Divisch had admirers in high places, among whom were
the Emperor Francis I. of Germany and his imperial consort, Maria
Theresa. Having been invited to Vienna, Divisch repaired to the Austrian
capital, where, with the aid of Father Franz, another electrical
devotee, he gave a demonstration of the wonderful capability of the new
form of energy before the grandees of the empire.
When he came to the electrical property of points, he showed their
discharging power in a very original way, one which must have made his
assistant uneasy for a while. At times, the machine worked by Father
Franz gave excellent results; at others, it failed to generate. It was
noticed by the critical few that when the machine failed, Divisch was
close by; while when it worked normally, he was at some distance away.
After a number of such alternations of success and failure which sorely
perplexed the assistant, himself a man of renown in Vienna, Divisch
explained the occurrence by saying, with a merry twinkle in his eye,
that the failure of the machine to generate when he was close to it,
apparently seeking out the cause of the breakdown, was due to a number
of pin-like conductors which he had concealed for the purpose in his
peruke and which neutralized the charge on the rotating generator!
The identity of the lightning of our skies with the artificial
electricity of our laboratories was suspected by many before the middle
of the eighteenth century. Englishmen like Hauksbee, Hall, Gray, Freke,
Martin and Watson; Germans like Bose and Winkler, and Frenchmen like
Abbé Nollet, had already published their suspicions and conjectures
anent the matter. Franklin, too, had indicated twelve points of analogy
between the two, in 1749, in his letter to Collinson, of London. Though
he felt the force of the analogical agreement, he also felt that the
matter could not be definitely settled without an appeal to experiment.
Accordingly, he added: "The electric fluid is attracted by points; we do
not know whether this property is in lightning. But since they agree in
all the particulars wherein we can already compare them, is it not
probable that they agree likewise in this? Let the experiment be made."
[Illustration: FIG. 19 The Divisch lightning conductor (1754)]
[Illustration: FIG. 20]
The experiment was made by Franklin himself by means of his kite two
years later, in the summer of 1752, and also by the lightning-rod which
he erected over his own house in the autumn of the same year. Doubtless
Divisch heard of the marvelous effects obtained from d'Alibard's
insulated conductor at Marly; at any rate, he erected in an open space
at some little distance from his rectory at Prenditz, a lightning
conductor 130 feet in height. As will be seen from the illustration, it
bristled with points, for the Bohemian wizard argued rightly that five
points would be more efficient than one, and 50 more efficacious than
five. The weird-looking structure destined to ward off the lightning of
heaven had no less than 325 well-distributed points. Lodge says in his
_Lightning Conductors_: "Points to the sky are recognized as correct;
only I wish to advocate more of them, any number of them, like barbed
wire along ridges and eaves. If you want to neutralize a thunder-bolt,
three points are not as effective as 3000." This was written in 1892;
nearly 140 years before that date, we find a simple parish priest of an
obscure village in Moravia using precisely such a multiple system of
short, pointed conductors for the protection of life and property. This
lightning conductor or _meteorological machine_, as Divisch called it,
was erected by him at Prenditz on June 15th, 1754. On the top of the rod
will be seen three light vanes, which were added in the interest of the
feathered race in order to prevent incautious members from incurring the
risk of electrocution by alighting on the apparatus during a storm. The
wind whirled the vanes round like the cups of an anemometer, and thus
kept the birds away from the zone of danger.
[Illustration: FIG. 21 Set of pointed rods]
Several trials came to the electrical Pastor, and from quarters least
expected. It happened in the second year after the erection of the
apparatus that the summer was unusually dry, in consequence of which the
crops failed almost completely. The farmers of the neighborhood were
always suspicious of the strange-looking mast of Prenditz; and, be it
said, that they were more than diffident about the propriety of
interfering with the forces of nature even under the plea of protection,
forgetting that they took great care to protect themselves against heat
and cold, rain, snow and hail. The country ladies, no doubt, used
parasols for one kind of protection; and the gentry, umbrellas for
another. Anyhow, the people of Prenditz and the good folk around did not
like the lofty mast, with its outstretched arms and bristling rows of
suspicious-looking iron points connected to the ground by means of four
long, heavy chains. For the nonce, they deemed their Pastor a queer
fellow, who thought that he could avert the anger of heaven by the
oddest kind of a machine which they ever laid their eyes on. It was
argued in the councils of the hamlets that, whatever advantages Divisch
claimed for his "machine," they were all of a negative character. It
_prevented_ the lightning stroke, he said; that might be, but they did
not _see_ the prevention. What they did see and keenly realize was the
failure of their crops. That affected them very closely; and if, as they
supposed, the apparatus of Prenditz had anything to do with it, the
sooner they got rid of the machine the better. Divisch, it must be said,
was liked by his people; but despite his popularity, the men of violence
carried the day and the machine was doomed. Popular passion, excited by
personal interest, got the better of the consideration due to the
Pastor. On an appointed day, a band of bellicose farmers came down on
the village and wrecked the apparatus which had cost the priest so much
thought and manual labor and on which, knowingly and justly, he relied
for the protection of the homesteads of his rustic flock.
This recalls a similar incident of mob violence which occurred at St.
Omer in the north of France, where a manufacturer of that quaint old
town, who had been in America and seen the usefulness of lightning
conductors, proceeded to erect one over his own house. Hardly was it
completed before the populace gathered together; and, when passion was
sufficiently aroused by inflammatory remarks of the demagogues, the
house was attacked and the conductor torn down. The manufacturer
complained of the inaction of the "gardiens de la paix" and appealed to
the courts to uphold his right to protect his home against lightning. He
entrusted his case to a young, brilliant lawyer, as yet unknown to fame,
but one destined to achieve unenviable notoriety during the
revolutionary period. This, the first defender of the lightning-rod in a
court of justice, was Robespierre.
The news of the untoward event soon reached the ears of the
Premonstratensian's superiors at Kloster-Bruck; and, as they very wisely
considered that the duty of a country priest is primarily to attend to
the spiritual welfare of his people, rather than to invent machines for
their protection against the bolts of heaven, they advised him to yield
to the prejudice of his people and not reconstruct the objectionable
apparatus.
Father Divisch accepted the friendly advice of his superiors and obeyed
like a good Premonstratensian monk. The remains of the shattered
"meteorological machine" were sent to the abbey at Bruck, where they
could be seen for many years afterward. As a consequence of this act of
vandalism, Divisch gave up experimenting with lightning-rods and with
electricity itself. The villagers were satisfied, but the world at large
lost the benefit that might accrue from the researches on atmospheric
electricity which Divisch would have carried on during the remaining
nineteen years of his life.
In giving up electricity, the disappointed priest turned his attention,
first, to acoustics and then, practical man as he was, to the
construction of musical instruments. It was not long before his genius
brought out an orchestrion of wind and stringed instruments which was
played like an organ with hands and feet, and which was capable of 130
different combinations. Prince Henry of Prussia offered a considerable
sum of money for the invention, but Divisch died while the preliminaries
of sale were arranging, and negotiations were broken off. The instrument
remained for many years in the abbey at Bruck, where it was in daily use
for the canonical office.
It is a curious coincidence that Franklin was also interested in musical
instruments. He is credited with having devised an improved form of
glass harmonica, one of which he presented to Queen Marie Antoinette.
Despite the bitter experience of Divisch, the introduction of lightning
conductors into Italy was warmly advocated some years later by Padre
Toaldo (1719-1797), an admirer and correspondent of Franklin. It was
through his influence and personal activity that the magnificent
thirteenth-century Cathedral of Siena was protected with lightning
conductors after having been repeatedly struck during the centuries and
seriously damaged. Toaldo published in 1774 his celebrated work on the
protection of public edifices and private buildings against lightning;
it contributed greatly to reassure public opinion on the value of
"Franklinian rods," as the conductors were commonly called.
It is a matter of regret that Franklin used the words "the electric
fluid is attracted by the points" in the passage quoted above, inasmuch
as in the popular mind such "attraction" courts rather than averts
danger. As already said, the rod no more "attracts" lightning than a
rain-pipe attracts a downpour. Franklin knew very well the twofold
function of his rods, the _preventive_, by which they tend to ward off
the stroke by gradually and silently neutralizing the excessive energy
of the cloud; and the other, the _preservative_, by which they convey
the discharge safely to earth when struck. He even complains of people
who concentrate their attention on the preventive function, forgetting
the other entirely, adding that, "Wherever my opinion is examined in
Europe, nothing is considered but the probability of these rods
preventing a stroke, which is only a part of the use which I proposed
for them; and the other part, their conducting a stroke which they may
happen not to prevent, seems to be totally forgotten, though of equal
importance and advantage." (1755.)
At a time, it was customary to make the rods rise to a considerable
height above the building, in the belief that the diameter of the circle
of protection was four times the height of the rod. Such a rule was an
arbitrary one which facts soon showed to be unreliable and unsafe. It is
now recognized that there is no such thing as a definite area of
protection.
Were this a literary chapter, we would point out that either of the
expressions "electric" storm or "lightning" storm is preferable to
_thunder-storm_, because electricity or lightning is the active agent or
principal feature of the impressive phenomenon. No one thinks of calling
a hailstorm by the descriptive term of _patter-storm_; yet that would be
just as logical and appropriate an appellative in one case as
thunder-storm is in the other.
_Thunder-tube_ is certainly a startling misnomer applied to the long,
narrow, glazed tubes formed in siliceous materials by the fervid heat of
the flash, but not in any way by the sound-waves produced by the crash.
_Thunder-bolt_ does not mean, despite the common opinion, a white-hot
mass that accompanies the discharge; it is purely and simply the flash
itself. A glowing mass that happens to come down in the track of the
discharge is a _meteorite_, a body of cosmic not terrestrial origin, a
visitor from space that chose the rarefied path of the flash for its
descent to earth.
Again, there are no _thunder-clouds_ in nature, only electric clouds or
lightning clouds; nor is there ever _thunder in the air_ save when the
lightning breaks from cloud to cloud, or leaps from cloud to earth, or
strikes from earth to cloud. But though thunder is only occasionally in
the air, electricity always is. We have a normal electrical field in all
seasons, times and places.
Though it is the lightning that kills and not the thunder, we would not,
however, object to the following inscription which we found on a
tombstone:
"Here lies (so and so), oh! what a wonder,
She was killed outright by a peal of thunder,"
because the suddenness of the peal may have given the aged lady a shock
from which her failing heart was unable to recover.
We are well aware that such criticism of technical terms in popular use
will have no reform effect whatever; because as long as people will say
"the sun rises" and "the stars set," they will continue to speak of
thunder-clouds and thunder-storms, thunder-tubes and thunder-bolts.
Though containing an element of error, these expressions have the
sanction of the centuries; and so, they have come to stay.
Returning to Divisch, that worthy priest and pioneer electrician died at
Prenditz in his sixty-ninth year, on Dec. 21st, 1765, and was buried in
the little churchyard where he had blessed many a grave during the
twenty-five years of his ministration. A simple inscription marks the
place of his interment, but a monument will soon be erected to his
memory which will tell the passerby where sleeps the Premonstratensian
pioneer of the lightning-rod.
About three months before the erection of his rod, _i.e._, in June,
1752, the idea occurred to Franklin that he could approach the region of
clouds just as well by means of a common kite. Here are his words anent
the novel and famous experiment with the "lightning kite":
"Make a small cross of two light strips of cedar, the arms so long
as to reach to the four corners of a large thin silk handkerchief
when extended; tie the corners of the handkerchief to the
extremities of the cross, so you have the body of a kite, which,
being properly accommodated with a tail, loop and string, will
rise in the air, like those made of paper; but this, being of silk,
is fitter to bear the wet and wind of a thunder-gust without
tearing. To the top of the upright stick is to be fixed a very
sharp-pointed wire, rising a foot or two above the wood. In the end
of the twine, next the hand, is to be held a silk ribbon, and where
the silk and cord join a key may be fastened. This kite is to be
raised when a thunder-gust appears to be coming on, and the person
who holds the string must stand within a door or window, or under
some cover, so that the silk ribbon may not be wet; and care must
be taken that the twine does not touch the frame of the door or
window. As soon as any of the thunder-clouds come over the kite,
the pointed wire will draw the electric fire from them, and the
kite with all the twine will be electrified, and the loose
filaments of the twine will stand out every way and be attracted by
an approaching finger. And when the rain has wetted the kite, so
that it can conduct the electric fire freely, you will find it
stream out plentifully from the key on the approach of your
knuckle. At this key the phial may be charged, and from electric
fire thus obtained spirits may be kindled and all the other
electric experiments be performed which are usually done by the
help of a rubbed glass globe or tube, and thereby the sameness of
the electric matter with that of lightning completely
demonstrated."[8]
Here we have the electric kite and manner of using it fully described
without, however, any direct statement that the author himself actually
experimented with it, although he does say that the experiment was
successfully carried out. This is strictly true, but it may be safely
contended that the precautions enumerated, the observation about the
fibres of the cord, its improved conductivity when wetted by the rain
and the like, all bespeak a knowledge of practical conditions that could
be obtained only by way of experiment.
But if Franklin is not outspoken on the matter, some of his
contemporaries are. Here is the kite incident as related in the
_Continuation of the Life of Dr. Franklin_, by Dr. Stuber, a
Philadelphian and intimate friend of the Franklins:
"While Franklin was waiting for the erection of a spire, it
occurred to him that he might have more ready access to the region
of clouds by means of a common kite. He prepared one by fastening
two cross-sticks to a silk handkerchief, which would not suffer so
much from the rain as paper. To the upright stick was affixed an
iron point. The string was, as usual, of hemp, except the lower
end, which was silk. Where the hempen string terminated, a key was
fastened. With this apparatus, on the appearance of a thunder-gust
approaching, he went out into the commons, accompanied by his son,
to whom alone he communicated his intentions, well knowing the
ridicule which, too generally for the interest of science, awaits
unsuccessful experiments in philosophy. He placed himself under a
shed to avoid the rain. His kite was raised. A thunder-cloud passed
over it. No sign of electricity appeared. He almost despaired of
success, when suddenly he observed the loose fibres of his string
move toward an erect position. He now presented his knuckle to the
key and received a strong spark. Repeated sparks were drawn from
the key, the phial was charged, a shock given, and all the
experiments made which are usually performed with electricity."
This testimony of a man who enjoyed the unlimited confidence of Franklin
has a very matter-of-fact ring about it; there is not a note of
uncertainty, not a word indicating doubt that his friend and neighbor
went out to the fields accompanied by his robust son, carrying along
with them a queer assortment of electrical impedimenta. This son,
William by name, was twenty-two years of age at the time; and as he died
in 1813, eleven years after the publication of Dr. Stuber's
biographical sketch, he had ample time to contradict the kite story if
instead of being a fact it were a mere romance. Nor is this all, for Dr.
Stuber's narrative, given above, appears textually in the "Memoirs of
the Life and Writings of Benjamin Franklin," edited by his grandson
William Temple Franklin. The Doctor, be it remarked, was very fond of
his grandson, whose "faithful service and filial attachment" he warmly
commends in several of his letters, and whose regard for the memory of
the statesman led him to undertake the task of preparing his works for
publication. On page 211, Vol. I., he tells us that "As Dr. Franklin
mentioned his electrical discoveries only in a very transient way, and
as they are of a most important and interesting nature, it has been
thought that a short disgression on the subject would be excusable and
not void of entertainment. For this purpose the following account of the
same, including the first experiment of the lightning kite, as given by
Dr. Stuber, is here given."
In these concluding lines we have the testimony of Franklin's grandson
to the authenticity of the "lightning kite" story. Moreover, the account
as given by Stuber evidently meets with his cordial approval, since he
transcribes it verbatim; and, as if to invest the quotations with
unimpeachable authority, he tells us in the preface, p. viii., that
"they deserve entire dependence because of the accuracy of the
information imparted."
A word now from Priestley, also one of Franklin's intimate friends. In
his _History of Electricity_, fourth edition, p. 171, he says that "Dr.
Franklin, astonishing as it must have appeared, continued actually to
bring lightning from the heavens by means of an electrical kite which he
raised when a storm of thunder was perceived to be coming on." Then
follows a description taken almost word for word from Dr. Stuber, whom
he styles "the best authority on the subject."
If, perchance, the above testimony should not be deemed conclusive and
final, all lingering doubt must be removed by Franklin's own words, for
in his _Autobiography_, after briefly referring to the experiments made
in France with pointed conductors, he adds: "I will not swell this
narrative with an account of that capital experiment (the pointed
conductor), nor of the infinite pleasure which I received on the success
of a similar one I made soon after with a kite at Philadelphia, as both
are to be found in histories of electricity."
Here, at last, we have Franklin's own word for it, that he made the kite
experiment, and that he made it "soon after" the demonstration of his
electrical discoveries which M. de Lor gave, by request, before Louis
XV. and his court.
The "lightning kite" is, therefore, not a myth, as some have ventured to
think, having been fully described by Franklin in his letter to Peter
Collinson, dated October 19th, 1752, and having been made by him some
time in June of the same year.
We have now to see whether Franklin was anticipated in the idea of the
kite or in its use for electrical purposes. There are some who hold that
he was anticipated by M. de Romas as to the idea, but not the actual
experiment; while others credit the French magistrate with both. Let us
examine the evidence which there is for these opinions.
M. de Romas lived in Nérac, a small town some seventy-five miles south
of Bordeaux. He was a member of the bar; and at the time of the
Franklinian furor in Europe was a judge of the district court. He took
an interest in scientific matters quite unusual for men of his
profession, proceeding, as soon as he had read of the efficiency of
pointed conductors, to study their behavior for himself. His experiments
met with surprising success, and were as much admired by the local
savants as they were dreaded by the common folk. Letters containing his
observations were regularly sent to the Academy of Bordeaux, where they
were read with lively interest on account of their character and
novelty. From the published _Actes_ of that body we learn that the first
kite used by de Romas was raised by him on May 14th, 1753.
Disappointment, however, attended this attempt, no electrical
manifestation being observed, although rain fell and wetted the hempen
cord. The magistrate of Nérac attributed his failure to the resistance
of the string; and, like a good electrician, surprisingly good for the
time, determined to improve its conductivity by wrapping a fine copper
wire round its entire length. When this long and tedious operation was
completed, he went out again to the fields on a stormy day, when,
assisted by two of his friends, he raised the kite and soon got torrents
of sparks from the wire-wound cord. This was on June 7th, 1753. The
experiment was repeated from time to time, both for his own satisfaction
and that of his assistants as well as for the entertainment of his
ever-growing class of admiring spectators. Kites 7-1/2 ft. long and 3
ft. wide were raised 400 and even 550 ft. above ground when flashes nine
feet long and an inch thick were drawn, so the account says, with the
report of a pistol. The effect must have been truly spectacular. The
kite was held by a silk ribbon fastened to the end of the hempen cord.
It is then a matter of history vouched for by the _Actes_ of the Academy
of Bordeaux that May 14th, 1753, is the day on which the first use of a
kite for electrical purposes was made in France; on the other hand, it
is to be remembered that Franklin flew his "lightning kite" in June,
1752, almost a year earlier. As far, then, as the _fact_ is concerned,
the Philadelphia philosopher was not anticipated by the Justice of
Nérac.
From facts let us pass to writings. Franklin's letter to Collinson, in
which he describes the electric kite, is dated October 19th, 1752, while
that of M. de Romas, on which the claim for priority is founded, was
addressed by him to the Academy of Bordeaux on July 12th, 1752, three
months earlier. After a lengthy and interesting account of his
experiments with pointed conductors, he concludes his communication as
follows:
"C'est là, Monsieur, ce qu'il y a de plus important, car j'aurais bien
d'autres particularités à vous communiquer; mais ma lettre, devenue
d'une excessive longueur, m'avertit de finir. Je me réserve de mettre au
jour la dernière (quoiquelle ne soit qu'un jeu d'enfant) lorsque je me
serai assuré de la réussite par l'expérience que je me propose d'en
faire et que je ne negligerai pas."
In English this would read: "Such, Sir, are the more important points
which I have to communicate, and to which many others might be added,
were it not for the excessive length of this letter, which warns me that
it is time to bring it to a close. I will, however, give publicity to
the last one of all (though it is only a child's plaything) as soon as I
shall have assured myself of its success by an experiment which I have
devised and which I shall not fail to make."
The words in brackets--"though it is only a child's plaything"--are all
important, for it is on them and on them alone that the claim for
priority has been put forth and maintained. It will be seen that the
word kite (_cerf-volant_), does not occur in the letter, so that there
can be no absolute certainty as to the nature of the _jeu d'enfant_
which the author had in mind, though it is very likely that the kite was
meant. In his _Mémoire sur les moyens de se garantir de la foudre dans
les maisons_, he says, after describing some experiments that he had
made with pointed rods: "Néanmoins toujours plein du désir d'augmenter
le volume du feu électricque, il fallut chercher le moyen pour y
parvenir. En conséquence, je me plongeai dans de nouvelles méditations.
Enfin une demi-heure après, tout au plus, le cerf-volant des enfants se
présenta tout à coup à mon esprit, et il me tardait de la mettre à
l'épreuve. Par malheur, je n'en avais pas le temps." In English: "Being
anxious to augment the quantity of electric fire, I began to think of
some means to effect my purpose, and soon became quite absorbed with the
subject. Not more than half an hour elapsed before the idea of the kite
suddenly occurred to me, and I longed for an opportunity to try it; but
unfortunately I had not sufficient leisure at the time." The work in
which this passage occurs was published at Bordeaux in 1776, shortly
after the death of the author. De Romas always maintained that he did
not borrow the idea of the kite from any one, but that it occurred to
him while pursuing his experiments with pointed conductors.
It must be admitted that de Romas could not have been acquainted with
Franklin's performance of June, 1752, when he sent to the Bordeaux
Academy his letter of July 12th, of the same year, for we cannot suppose
that in an age of sailing vessels such news would cross the Atlantic and
reach an obscure provincial town in the southwest of France in the space
of a month. On the other hand, it is equally improbable that a vague
allusion to the electrical use of a kite made at Nérac on July 12th, by
a man entirely unknown to fame as was de Romas, should be talked of on
the banks of the Schuylkill before October 19th, the date of Franklin's
memorable letter to Collinson. Moreover, the "_jeu d'enfant_" allusion
as well as the very use of the kite by de Romas failed so completely to
attract the attention of scientific men of his own country that he
frequently and bitterly complained down to the end of his life, in 1776,
of their persistent neglect of his claims to recognition.
From all this, we conclude:
(_a_) That Franklin's "lightning kite" is not a myth, the experiment
having been made by him in June, 1752, and fully described by him in a
memorable letter written to Peter Collinson, of London, dated October
19th of the same year:
(_b_) That de Romas independently had the idea of using a kite for
electrical purposes as early as July 12th, 1752; but that he did not
carry out his idea until May 14th, 1753; and, furthermore, that he did
not succeed in getting any electrical manifestations until June 7th,
1753, his success then being due, at least in part, to the clever idea
which he had of entwining the cord with a fine copper wire. Therefore,
_suum cuique_.
In conclusion, we would say that the cardinal and enduring achievements
of Franklin are:
(1) His rejection of the two-fluid theory of electricity and
substitution of the one-fluid theory; (2) his coinage of the
appropriate terms _positive_ and _negative_, to denote an excess or a
deficit of the common electric fluid; (3) his explanation of the Leyden
jar, and, notably, his recognition of the paramount role played by the
glass or dielectric; (4) his experimental demonstration of the identity
of lightning and electricity; and (5) his invention of the lightning
conductor for the protection of life and property, together with his
clear statement of its preventive and protective functions.
If Franklin was well acquainted with electrical phenomena, it is safe to
say that his knowledge of human nature was wider and deeper still. This
appears continually in his _Autobiography_, in his political writings,
in business transactions and diplomatic relations.
On one occasion, while his re-election as clerk of the General Assembly
was pending, a certain member made a long speech against him. Franklin
listened with calm, dignified composure; and after his election, instead
of resenting the opposition of the offending member, he determined that
it would be better to disarm his antagonism and win his friendship. For
this purpose he sent the assemblyman a courteously-worded request for
the loan of a very scarce book which was in his library. The book was
sent to Franklin, who returned it within a week with a note of thanks,
which had the desired effect. Commenting on the event, our philosopher
says that "it is more profitable to remove than to resent inimical
proceedings."
Some of Franklin's views on general political economy are tersely set
forth in the following passage: "There seem, in fine, to be but three
ways for a nation to acquire wealth. The first is by _war_, as the
Romans did in plundering their conquered neighbor; this is _robbery_.
The second is by _commerce_, which is generally _cheating_. The third is
by _agriculture_, the only _honest way_ wherein man receives a real
increase of the seed thrown into the ground, in a kind of continual
miracle wrought by the hand of God in his favour, as a reward for his
innocent life and virtuous industry."
Franklin asserts his religious convictions in many passages of his
"Autobiography" as well as on many occasions of his public life. Shocked
by "Tom" Paine's views of fundamental religious truths, he says: "I have
read your manuscript with some attention. By the argument which it
contains against a particular Providence, though you allow a general
Providence, you strike at the foundation of all religion. For, without
the belief of a Providence that takes cognizance of, guards and guides,
and may favour particular persons, there is no motive to worship a
Deity, to fear His displeasure, or to pray for His protection. I will
not enter into any discussion of your principles, though you seem to
desire it. At present, I shall only give you my opinion that, though
your reasonings are very subtile and may prevail with some readers, you
will not succeed so as to change the general sentiments of mankind on
that subject; and the consequence of printing this piece will be a great
deal of odium drawn upon yourself, mischief to you, and no benefit to
others. He that spits against the wind, spits in his own face."
This aphorism recalls the ripe wisdom contained in many of the sayings
of "Poor Richard," for Franklin was a deep thinker, shrewd observer and
quaint expositor of his own philosophy. Continuing, he fleeces Paine in
the following noble words: "But were you to succeed, do you imagine any
good would be done by it? You yourself may find it easy to live a
virtuous life without the assistance afforded by religion; you having a
clear perception of the advantages of virtue and the disadvantages of
vice, and possessing strength of resolution sufficient to enable you to
resist common temptations. But think how great a portion of mankind
consists of weak and ignorant men and women, and of inexperienced,
inconsiderate youth of both sexes, who have need of the motives of
religion to restrain them from vice, to support them to virtue, and
retain them in the practice of it till it becomes _habitual_, which is
the great point for its security. And perhaps you are indebted to her
originally, that is, to your religious education for the habits of
virtue upon which you now justly value yourself. You might easily
display your excellent talents of reasoning upon a less hazardous
subject, and thereby obtain a rank with our most distinguished authors.
For among us, it is not necessary, as among the Hottentots, that a
youth, to be raised into the company of men, should prove his manhood by
beating his mother."
Franklin concludes this magnificent expression of his religious faith by
the solemn warning: "I would advise you, therefore, not to attempt
unchaining the tiger, but to burn this piece before it is seen by any
other person; whereby you will save yourself a great deal of
mortification by the enemies it may raise against you, and perhaps a
good deal of regret and repentance. If men are so wicked _with_
religion, what would they be _without_ it?"
Franklin's belief in the cardinal doctrine of the resurrection of the
body is well expressed in the epitaph which he wrote for himself in
1728, when in his twenty-second year. It reads
The Body
Of
Benjamin Franklin
Printer,
(Like the cover of an old book
Its contents torn out
And stript of its lettering and gilding)
Lies here, food for worms.
But the work shall not be lost
For it will (as he believed) appear once more
In a new and more elegant edition
Revised and corrected
By
The Author.
However, when the statesman and philosopher was laid at rest beside his
wife in the Cemetery of Christ Church, Philadelphia, in 1790, the marble
slab which marked the grave bore no other inscription than Franklin's
name and the date of his death.
Appreciating the great loss which the country sustained by the death of
Franklin, Congress ordered a general mourning for one month throughout
the fourteen States of the Union; and the French National Assembly
decreed three days of public mourning at the instance of Mirabeau, who
said in his address that "The genius that gave freedom to America and
scattered torrents of light upon Europe, has returned to the bosom of
the Divinity. Antiquity would have erected altars to that mortal who for
the advantage of the human race, embracing both heaven and earth in his
vast mind, knew how to subdue both thunder and tyranny."
The fugitive apprentice boy of 1723 turned out to be one of the most
esteemed and eminent Americans of his day. Of an even temper and
well-balanced mind, he was plain in dress, simple in manner, easy of
approach and friendly to all. The success which he achieved during his
long career of eighty-five years, shows what may be done by seizing the
opportunities which come to every one, by concentration of mind,
application to duty and tenacity of purpose. He attained distinction in
science, in letters, in diplomacy; he stood for good government and true
liberty. His name is a household one in his own country, where
monuments, institutions and cities will bear it down to posterity.
ADDENDA.
_The Lightning Kite._
Fully described by Franklin in a letter to Peter Collinson, of London,
dated October 19th, 1752.
Stuber in his "Continuation of the Life of Dr. Franklin," and Priestley
in his "History of Electricity," affirm that Franklin made the
experiment in June, 1752.
Franklin's son, William, never denied the story, although he figured in
it as an active character.
William Temple Franklin, who prepared for publication his grandfather's
works, gives the kite story almost verbatim from Stuber.
Finally, Franklin himself states that he made the experiment: Memoirs,
Vol. I., p. 164.
_Franklin and de Romas._
June, 1752: Franklin raises his kite in a field near Philadelphia.
July 12, 1752: Letter of de Romas to the Academy of Bordeaux, in which a
probable reference is made to the kite as _un jeu d'enfant_.
October 19th, 1752: Franklin describes the "lightning kite" in a letter
to Peter Collinson, of London.
May 14th, 1753: First use by de Romas of the electric kite in the fields
around Nérac; no result.
June 7th, 1753: First success by de Romas with his electric kite.
_Pointed Conductor._
Suggested by Franklin in letter to Peter Collinson, of London, dated
July 29th, 1750.
D'Alibard, following Franklin's instructions, gets torrents of
discharges from his iron rod 40 feet high at Marly, May 10th, 1752.
De Lor gets good results from his conductor 99 feet high, erected over
his house in Paris, May 18th, 1752.
De Buffon succeeds with his rod on May 19th, 1752.
Franklin erected the first rod over his house in Philadelphia in
September, 1752. It was made of iron with a sharp steel point rising
seven or eight feet above the roof, the other end being sunk five feet
in the ground. Franklin charged a Leyden Jar from his rod in April,
1753. Professor Richmann, of St. Petersburg, was killed by a flash from
his apparatus on August 6th, 1753.
BROTHER POTAMIAN.
[Illustration: ALOISIO GALVANI]
FOOTNOTES:
[8] Scientific Writings of Joseph Henry, Vol. I., p. 201.
[9] Frequently referred to as Lullin's experiment.
[10] Every schoolboy knows that the electricity which passed
down the kite-string was not drawn from the clouds, but was due to their
inductive action on the pointed conductor attached to the kite. Kant
calls Franklin the "Modern Prometheus."