COULOMB.
Great discoverers in science must usually be satisfied with having their
names attached to some one phase of scientific development, be it an
instrument, a law, a unit of measurement, a process of investigation or
some phenomenon which they first observed. The originality of Coulomb's
genius will be better appreciated, since besides having a unit of
electricity named after him, there is also a law in electro-magnetics
and a torsion-balance that will always be associated with his name. Few
men have been more ingenious in their ability to put complex ideas into
practical shape and give them simple mechanical expression by
instrumental methods. While his name is to be forever associated with
the science of electrostatics, he was profoundly interested in other
departments of physics, and for him to be interested always meant that
he would illuminate previous knowledge by practical hints and
suggestions and carry the conclusions of his predecessors a little
farther into science than they had ever gone before. His was typically
an experimental genius, and he must be considered one of the men of whom
not more than half a dozen are born in a century, who are, in Kipling's
strong term, "masterless"; who do not need to be taught, but who find
for themselves a path into the domain of the unknown.
Coulomb investigated the fundamental law in electricity and magnetism,
that attractions and repulsions are inversely as the square of the
distances, and showed that it held accurately for point-charges and
point-poles. He demonstrated that these interesting phenomena were not
chance manifestations of irregular forces, but that they represented a
definite mode of action of force, thus setting this department of
knowledge on a scientific basis. While in practical significance Ohm's
Law, discovered nearly a half century later, is of much more import,
Coulomb's discoveries are fundamental in character and, coming in the
very beginnings of modern electrical science, did much to guide the
infant science in the ways it should follow. The establishing of this
law contributed very largely to the rapid development of the twin
sciences of electricity and magnetism. It is experimental observation
that means most for a rising science; and, in fact, that Coulomb should
have been the pioneer in it stamps him as possessed not only of great
originality, but also of the power of independent thinking, which is
perhaps the most precious quality for the man of science.
The French investigator succeeded in demonstrating his law by two
distinct methods which are still used for illustration purposes in our
physical laboratories. In the first, he employed the torsion-balance
devised by Michell, and re-invented by himself, an instrument of exact
measurement which, in his hands, yielded as invaluable results as it did
in those of Faraday half a century later. The instrument depends on the
principle first established by Coulomb himself, that when a wire is
twisted, the angle of torsion is directly proportional to the force of
torsion. In the application of this principle, a fine wire is suspended
in a glass case, on the sides of which there is a graduated scale to
measure the degree of repulsion between two like poles of a magnet or
between similarly electrified bodies.
In his second research on the law of the inverse square, Coulomb used
what is known as the method of oscillations. A magnetic needle swinging
under the influence of the earth's magnetism is known to act like a
pendulum, and as such obeys the laws of pendular motion. In applying
this method, Coulomb caused the magnetic needle to oscillate, first,
under the influence of the earth's magnetism alone and then under the
combined influence of the earth and the magnet placed at varying
distances from the needle. The most interesting feature of this work is
the manner in which Coulomb succeeded in eliminating the important
factor of the earth's magnetism from the problem. It is so simple and
ingenious that it commands the admiration of investigators, who employ
it in their laboratory work even to the present day.
It is clear, then, that the International Committee which selected the
term coulomb for the electromagnetic unit of electrical quantity gave
honor where it was eminently due. Coulomb stands out as a man of
precision and accuracy, whose methods of exact measurement
revolutionized the rising science, and whose researches and discoveries
in physics and mechanics furnish ample justification for giving him a
place among the makers of electricity. He was one of the gifted men
whose original works ushered in so gloriously the nineteenth century,
and who laid the deep and firm foundations on which the last three
generations have built up the magnificent temple of electrical science.
Charles Augustin de Coulomb was born at Angoulême, June 14th, 1736. His
ancestors for several generations had been magistrates, and were looked
upon as representatives of the country nobility. He made his university
studies in Paris, and while still young, entered the army. From the
very beginning, however, his genius for mathematics was recognized, and
he was employed in the capacity of military engineer. To Americans, it
will be interesting to know that his first engineering project was
undertaken at Martinique, where he constructed Fort Bourbon. His
sterling character and remarkable ability secured him rapid advancement
in the service. In spite of the fact that the climate did not agree with
him, he remained for three years on the island, because he would not
employ the political influence that might have secured his recall, since
he thought it his duty to serve his country in an important colonial
post. Nearly all his comrades perished by fever. It is the irony of fate
that after his return to France a change in the ministry deprived him of
the just recompense of his devotion to country, and he did not receive
the special extraordinary promotion which he had earned in this special
detail.
During a short stay that he made at Paris after his return, he sought
the society of men of science as far as possible, and succeeded in
getting in touch with all that was most promising in scientific progress
at the time. He was already known rather favorably by many of the
scientific men of the capital because of the paper on The Statics of
Vaults, a monograph on static problems in architecture, which he
presented to the Academy of Sciences in 1779. His next military
assignment was to Rochefort. Here he composed his monograph on "The
Theory of Simple Machines," which carried off the double prize that had
been offered by the Academy of Sciences for the solution of problems
connected with this important question. This attracted the attention not
only of the scientific world, but also of his military superiors. As a
result, he was sent successively to Cherburg and to the Isle of Aix, to
direct engineering works, and accomplished the tasks involved with
success.
Two years later, when he was about forty-five years of age, he was
elected member of the Academy of Sciences by a unanimous vote. He was a
man of great personal magnetism, and all those who came in contact with
him learned to like him for his straightforward character and for the
absolute righteousness of his life. Few men have made firmer friends
than Coulomb, as few have ever shown more unselfish devotion to duty and
to conscience than he, though under circumstances that were neither
spectacular nor theatrical. It was harder to face the deadly climate of
Martinique than it would have been to take one's place at the head of a
forlorn hope in an outburst of enthusiastic courage; and Coulomb was to
have other trials of quite as deterrent a nature, and was to meet them
with the same imperturbed sense of duty.
Graft is sometimes supposed to be temptation peculiar only to our own
times, but the opportunities for it have always been present in such
work as Coulomb had to oversee, and the army engineer of all ages has
had to stand or fall before it. It was proposed, about this time, to
build a system of government canals in Brittany. Such a canal-system
would, as is easy to understand, cost an enormous sum of money and give
magnificent opportunities for speculation of various kinds. No small
objection had been made to the project, on the score that it would not
confer all the benefits on the region that were claimed for it, and
Coulomb was commissioned by the Minister of Marine to determine the
question of the advisability of constructing the canals, and of the
probable effect which they would have on the commerce of the country.
After careful investigation, he came to the conclusion that the
advantages which were expected to accrue from the project would not
compensate for the enormous expense that would be entailed. This
decision aroused the angry protest of a strong political faction, who
expected to reap wealth and personal advantages of many kinds from the
scheme, and who protested bitterly against Coulomb's report. He was able
to support his conclusions in the matter, however, with such
unanswerable mathematical and engineering arguments, that his opinion
prevailed and the project was given up.
As a consequence, instead of the opportunity to serve a political party
with every avenue to preferment and, above all, to wealth open for him,
he found himself, for the time being, deprived even of the opportunity
to devote himself further to his favorite occupations in military
engineering. The excuse given for this interruption in his career, for
there has always been an excuse for such action, was that proper
representations for permission to make the report had not been made to
the Minister of Marine; and instead of commendation, Coulomb received
what was practically a reprimand.
Wounded by this injustice, which was manifestly due to the fact that his
honest report had displeased those who expected to reap personal benefit
from the canal project, and disgusted with a service in which such
things were possible, Coulomb sent in his resignation. The Minister of
Marine realized that the acceptance of the proffered resignation would
surely expose the ministry at least to suspicion as to the reasons why
Coulomb's report was not accepted with good grace. Permission to retire
from the service was refused, as this would insure his silence. He was
ordered back to Brittany to continue his work there, possibly with the
idea that this unfavorable experience would be sufficient of itself to
make him understand what was expected of him and render him a little
more complacent to the wishes of those in authority. If any such ideas
were entertained, they were destined to grievous disappointment. Coulomb
was not of those who, seeing duty plainly, refuse to follow it because
some personal advantage or disadvantage intervenes. Selfish reasons did
not appeal to his character nor obscure the issues.
He went back to Brittany, ready to express his firm opinion in the
matter and with integrity of soul untouched. The consequence was that
the provincial authorities, recognizing their true interests,
acknowledged the error they had come near falling into, and now wished
to reward the engineer handsomely for his unswerving devotion to duty.
Coulomb as promptly refused a reward for doing his duty as he had
ignored even the appearance of a bribe to avoid it. Only after
considerable pressure was he prevailed upon to accept the best timepiece
they could procure, on which the arms of the province were engraved. It
had what was quite rare in those days, a second's hand, and he
constantly made use of this in all his experimental work thereafter. A
French biographer says that, never was a souvenir better chosen nor more
suitably employed. Coulomb's merits were recognized by the government
authorities not long after, and he was made superintendent of the
fountains of France. A few years later, he was promoted to the position
of Curator of Plans and Relief Maps of the Military Staff of France,
and was chosen as one of the commission of the French Academy of
Sciences who went to England in order to study hospital conditions
there. At this time, he was at the acme of his career. His grade was
that of Lieutenant Colonel of Engineers, a position much higher in the
foreign armies at that time than would be the post with the
corresponding title in our army. He had been made a Chevalier of St.
Louis, and it looked as though a brilliant future were opening out
before him. Each year, for a decade, had seen the publication of one or
more memoirs on important subjects, nearly every one of which contained
some original material of the highest value, destined not only to add to
Coulomb's reputation, but to furnish basic information for the further
development of science.
In 1789, however, the Revolution broke out, and there was an end to all
Coulomb's opportunities for work. He was utterly out of sympathy with
the movement, the worst consequences of which he foresaw from the
beginning, and he at once handed in his resignation of the various
positions that he occupied under the government. He went into almost
absolute retirement, devoting himself to the education of his children.
During this time, however, he did not cease to cultivate science,
inasmuch as he gave the finishing touch to various papers which he had
previously outlined. Unfortunately, however, his departure from Paris
made it impossible for him to continue his investigations in electricity
for want of apparatus, and so there is a ten years' interruption in his
life of scientific activity and of original work. Besides, it cannot be
surprising that he should not have had the heart to go on with his work
under the awful social conditions that prevailed. Many of his friends
lost their lives during the stormy period of the Revolution; most of
the others were banished or were in hiding. His beloved country had gone
into an unfortunate eclipse, as he could not help but consider it; most
of the nations of the earth were indeed in league against her, and the
end was not yet in sight. It would be too much to expect of human nature
that it should devote itself to abstruse problems in science at moments
of such disturbance as this, and so some of the possibilities of
Coulomb's original genius were lost to science during that calamitous
period.
Like many of the great discoveries of science, Coulomb's most important
work was done in the course of other investigations, and came by what
might be called a happy accident. He had been investigating the
qualities of wire of various kinds, especially with regard to their
elasticity, so as to be able to determine the limits of their use in
various engineering projects. When he discovered that the elasticity of
torsion of a wire was a constant property, he proceeded to utilize it in
the calculation of such delicate phenomena as those of electric and
magnetic forces. The first instrument for this purpose that he
constructed consisted simply of a long magnetized needle suspended
horizontally by a fine wire. Supposing this needle to be at rest, if one
moves it away from the magnetic meridian by a certain number of degrees,
the twisted wire will have a definite tendency to untwist and to bring
back the needle to its original position by a series of oscillations
whose frequency can be readily observed.
For such observations, it is possible to obtain the value of the force
acting on the needle and causing it to move to and fro at a given rate.
This was the underlying idea which received very simple expression in
the ingenious instrument which Coulomb devised and called a
torsion-balance. With it, he set about determining the law which governs
the mutual action of magnets and of electrified bodies with regard to
distance, and found it to be the same as that which Newton found to hold
for bodies distributed throughout the universe, that is, that attraction
and repulsion vary inversely as the square of the distance. He also
proved, with the aid of his torsion-balance, that the forces of
attraction and repulsion vary as the product of the strength of the
poles in one case and as the product of the electric charges in the
other. These were the important discoveries of Coulomb's life; they
served to earn for him the right to have his name given to the unit of
electrical quantity, the _coulomb_.
Coulomb did not stop here, however, but proceeded to apply his laws to
various other phenomena. He proved that electricity distributes itself
entirely over the surface of a body without penetrating the mass of the
conductor, and he showed by calculation that this result was a necessary
consequence of the law of repulsion.
A list of the papers which he published on electricity and magnetism,
the titles of which, with French accuracy of expression, furnish an
excellent idea of their contents, shows the thoroughly progressive and
scientific spirit of the man, and how well he proceeded from the known
to the less known, always widening the bounds of knowledge. Suffice it
to say here that the observations of Coulomb were not only original, but
that they concerned some of the most difficult questions in
electricity, and that he was clearing the ground for others in such a
way as to make future work and quantitative measurements in electricity
reliable and comparatively easy. It is because of this pioneer work that
Coulomb deserves so much praise. It was not long before Coulomb's
observations were confirmed by others, and then the beginnings of the
modern development of electricity became manifest, owing not a little to
the researches and inventions, the genius and ingenuity of this French
military engineer.
Some phases of electrical development attributed to others really belong
to Coulomb. A typical example of this detraction from his merit is the
attribution to Biot of the solution of the problem of the complete
discharge of an electrified sphere by means of two hollow hemispheres.
This experiment is fully described by Coulomb, and he even emphasizes
the fact that the external discharging bodies need not necessarily be of
the same shape as the charged sphere. Some of what Coulomb accepted as
principles in electricity have proved in the course of time, not to be
the realities that he thought them; but the progress that has led to
such contradictions of his opinions has been mainly rendered possible by
his own discoveries. The fable of the eagle stricken by the arrow
containing some of its own feathers, is so old that one might think
that, when the progress of a science due to a scientist brings men
beyond the position he occupied, they would not blame him for
backwardness. This is, however, one of the curious critical methods in
the history of science that has most frequently to be deprecated by the
historian who is tracing origins and developments.
Coulomb's papers, with the exception of his memoir on "Problems in
Statics Applied to Architecture," his "Researches on the Methods of
executing Works under Water without the Necessity of Pumping," his
"Theory of Simple Machines," and his researches "On Windmills," which
form separate monographs, were all published together in a single volume
by the French Physical Society in 1884.[22]
This volume contains, besides his investigations on the best way of
making magnetic needles, his theoretic and experimental investigations
on the force of torsion and on the elasticity of metallic threads, which
were undertaken in order to enable him to make his electric
torsion-balance something more than mere guess-work. All the other
papers are concerned directly with electricity or magnetism, and show
how actively, nearly a hundred and twenty-five years ago, a great mind
was engaged with problems in electricity which we are apt to consider as
belonging more properly to our own time. The list of papers published in
these memoirs, arranged in chronological order, gives a good idea of the
development of electrical science in Coulomb's own mind. There is a
logical as well as a chronological order to be observed in them.
In 1785, when he was just approaching his fiftieth year, there were
three subjects with regard to which Coulomb's experimental observations
enabled him to set down some definite principles. The first of these was
the construction and use of an electric balance, founded on the
property which wires have of exhibiting a torque proportional to the
angle of torsion. The second was the determination of the laws,
according to which the magnetic and electric "fluids," as Coulomb and
investigators in electricity called them at that time, act both as
regards repulsion and attraction. The third was the determination of the
quantity of electricity which an insulated body loses in a given time
from contact with air more or less moist.
In 1786, he published a paper in which he demonstrated what he
considered the principal properties of the electric fluid. These are,
that this fluid does not spread itself on a substance by any chemical
affinity or any elective attraction, but that it distributes itself over
various bodies that are placed in contact, entirely in accordance with
their shape; and also that in electrical conductors, the charge is
limited to the surface of the conductor and does not penetrate to any
appreciable depth.
In 1787, his only paper was on the manner in which the electrical fluid
divides itself between two conducting bodies placed in contact, and on
the distribution of this fluid over the different parts of the surface
of these bodies. He continued his investigations into this subject in
1788, and also succeeded in determining the density of the electricity
at different points on the surface of conducting bodies.
In 1789, he began to work more particularly on magnetism. His first
paper on the subject was published that year. Unfortunately, as we have
said, the Revolution interrupted his scientific investigations at this
point, and for the next eleven years we have nothing from his pen. As a
nobleman, he was compelled to leave Paris, and this not only put him out
of touch with scientific work generally, but deprived him of the
opportunities of using such apparatus as was necessary to carry on his
experiments. That he acted prudently in leaving Paris, the careers of
other scientists amply prove. Lavoisier continued to carry on his
chemical investigations during the stormy times of the Revolution, but
his stay in the capital eventually cost him his life. Abbé Haüy, the
father of crystallography,[21] who, because of his contributions to the
science of pyro-electricity, is of special interest to us, continued to
work at his crystals throughout even the Reign of Terror. When thrown
into prison, he asked and obtained permission to have his crystals with
him. His friends saved him from Lavoisier's fate, but not without an
effort, as his life was seriously endangered.
It is easy to understand, however, that a member of the nobility like
Coulomb, whose life had been spent in military affairs, should not be
able to devote himself seriously to scientific matters while his country
was in such a turmoil.
In 1801, he resumed his investigations once more, but now they are
concerned more particularly with magnetism. The first was a theoretical
and practical determination of the forces which hold different magnetic
needles, magnetized to saturation, in the magnetic meridian. This was
followed, in the same year, by a paper which, like its predecessor, was
published among the memoirs of the Institute of France, which had
replaced the Royal Academy of Sciences, to which body many of Coulomb's
papers of the former time had been presented, and in whose publications
they originally appeared. This second paper detailed his experiments on
the determination of the force of cohesion of fluids and the law of
resistance in them, when the movements were very slow.
When the French Institute was organized under Napoleon in 1801, Coulomb
was named among its first members. It is believed that he was even
chosen to occupy a place in the first government of the state, but a man
more interested in politics obtained the place, a fortunate circumstance
for science. Coulomb was named, however, one of the inspectors of public
instruction, then the highest place in the education department, and he
did much to restore to France the educational system that had been
destroyed during the Revolution. In this rather trying work he was noted
for the kindliness yet firmness of his character, while his absolute
fairness and sense of justice were recognized on all sides.
Unfortunately Coulomb was not long spared to continue his work. He took
up his experimental and mathematical investigations, on his return to
the capital, with great enthusiasm, but his health had been undermined
and his work had been rudely interrupted. After 1801, no further paper
by him appears to have been published until 1806. This gave the result
of different methods employed in order to produce in blades and bars of
steel the greatest degree of magnetism. For some time preceding this, in
spite of increasing ill-health, he had continued his experiments on the
influence of temperature on the magnetism of steel. His work on this
subject was not destined to be completed, for not long after passing his
seventieth year, in June of this year, his health gave way completely,
and he died August 23d, 1806. His final observations were gathered by
Biot, carefully preserved, and assigned a place in the volume of
Coulomb's Memoirs, issued by the French Physical Society.
Personally, Coulomb was noted for great seriousness of character, though
with this was mingled a gentleness of disposition that made for him some
cordial friendships among his scientific contemporaries. He had but few
friends, but those who were admitted to his intimacy made up by the
depth of their affection for the smallness of their number. Even those
who had occasion to meet him but once or twice, carried away from their
meeting an affectionate remembrance of his kindliness and courtesy and
readiness to help wherever he could be of service. He was extremely
happy in his family relations, and this proved to be a great source of
consolation to him during the years when the progress of the French
Revolution took him away from science and made him almost despair of his
country.
It is not surprising that Biot, the great French physicist, in writing
of Coulomb in his Mélanges Scientifiques et Littéraires, Vol. III.
(Paris, 1858), should have held Coulomb up as a model of the simple,
earnest, helpful life and as a man of the most exemplary character. He
says: "Coulomb lived among the men of his time in patience and charity.
He was distinguished among them mainly by his separation from their
passions and their errors, and he always maintained himself calm, firm
and dignified _in se totus teres atque rotundus_, as Horace says, a
complete, perfect and well-rounded character." Few men have deserved so
noble a eulogy as this, written nearly fifty years after his death, by
one who had known Coulomb himself and his contemporaries well; it has
none of the exaggeration of a funeral panegyric, and is evidently
founded on details of knowledge with regard to the great electrician
which had become a tradition among French scientists, and which Biot
has forever crystallized into the history of science by his emphatic
expression.
One could scarcely wish for a better epitaph than Biot's summing up of
Coulomb's personal character: "All those who knew Coulomb know how the
gravity of his character was tempered by the sweetness of his
disposition, and those who had the happiness to meet him at their
entrance into a scientific career have kept the most tender remembrance
of his gentle good-heartedness."
[Illustration: HANS CHRISTIAN OERSTED]
FOOTNOTES:
[21] Collection de Memoires relatifs à La Physique Publiés Par
la Société Française de Physique. Tome I., Mémoires de Coulomb. Paris.
Gauthier-Villars, Imprimeur-Libraire Du Bureau des Longitudes, de
L'École Polytechnique, Quai des Augustins, 55, 1884.
[22] Catholic Churchmen in Science, the Dolphin Press,
Philadelphia, 1906.