containing rarefied gases for experimentation. He partially exhausted
his tubes of air, introduced into them permanent and sealed platinum
electrodes, and produced those wonderful effects by the discharge
obtained by connecting the electrodes with the terminals of an electric
machine or induction coil, which from their novelty and beauty became
known as Geissler effects, just as his tubes became known as Geissler
tubes. In the attenuated atmosphere of the Geissler tube, the current
does not pass directly from one platinum point or electrode to the
other, but, instead, illuminates the entire atmospheric space. When
other gases are introduced in rarefied form, they are similarly
illuminated, but in colors corresponding to their composition. In his
further experiments, Geissler noted that the gases in the tube behaved
differently at the anode, or positive terminal, and the cathode, or
negative terminal. A beautiful bluish light appeared at the cathode,
while the anode assumed the same color as the illuminated space in the
tube. It was also noted that after the electric discharge within the
tube, there remained upon the inner surface of the glass a fluorescent
or phosphorescent glow, which was attributed to the effect of the
cathode.
[Illustration: GEISSLER’S TUBES.]
This brought the study of the _cathode_ rays into prominence, and
through the investigations of Professor William Crookes, in 1879 and
afterwards, a conclusion was reached that a “Fourth State of Matter”
really existed. He perfected tubes of very high vacuum, by means of
which he showed that molecules of gas projected from the cathode moved
freely and with great velocity among one another, and so bombarded the
inner walls of the tube as to render it fluorescent.
Subsequently, Hertz showed that the cathodic rays would penetrate thin
sheets of metal placed within the tube or bulb; and soon after, Paul
Lenard (1894) demonstrated that the cathodic ray could be investigated
as well outside of the tube or bulb as within it. He set an aluminum
plate in the glass wall of the bulb opposite the cathode. Though
ordinary light could not penetrate the aluminum plate, it was readily
pierced by the cathodic rays, to a distance of three inches beyond its
outside surface. With these rays, thus freed from their inclosure, he
produced the same fluorescent effects as had been noted within the
bulb, and even secured some photographic effects. These cathodic rays
produced no effect on the eye, which proved their dissimilarity to
light. Lenard showed further that the cathodic rays outside of the tube
could be deflected from their straight course by a magnet, that they
might pass through substances opaque to light, and that in so passing
they might cast a shadow of objects less opaque, which shadow could be
photographed. Now Professor Roentgen came upon the scene. He had been
conducting his experiments in Germany, along the same lines as Lenard,
and had reached practically the same results as to the penetrative,
fluorescent, and photographic effects of the cathodic rays. But he
had gone still further, and, in 1896, fairly set the scientific world
aflame with the announcement that all the effects produced by Lenard
in the limited space of a few inches could also be produced at long
distances from the tube, and with sufficient intensity to depict solid
substances within or behind other substances sufficiently solid to
be impermeable by light. Professor Roentgen claims that his X ray is
different from the cathodic ray of Lenard and others, because it cannot
be deflected by a magnet. This claim has given rise to much controversy
respecting the real nature of the X ray, a controversy not likely to
end soon, yet one full of inspiration to further investigation.
[Illustration: SCIAGRAPH OR SHADOW PICTURE.
By X Ray process.]
The essential features of the best approved apparatus designed to
produce the X ray and to secure a photograph of an invisible object,
are: (1.) A battery or light dynamo as a generator of the electric
current, accompanied, of course, by the necessary induction coil,
which should be so wound as to give a spark of at least two inches in
length in the tube where a picture of a simple object, as a coin in
a purse, is desired; a spark of four inches in length where pictures
of the bones of the hands, feet, or arms are desired; and a spark of
from eight to ten inches in length where inside views of the chest,
thighs, or abdomen are desired. (2.) The second essential is the glass
tube. The one in common use is the Crookes tube, usually pear-shaped,
and resting upon a stand. Into it is inserted two aluminum electrodes
or disks, the one through the smaller end of the tube being used as
the cathode, and the one from below and near the large end being used
as the anode. (3.) A fluoroscope with which to observe the conditions
inside the tube necessary to the production of the X ray, to decide
upon its proper intensity, and to establish the proper degree of
fluorescence. The favorite fluoroscope for this purpose is the one
invented by Edison. It is in the form of a stereopticon, in which
is a dark chamber after the manner of a camera. In front are two
openings, admitting of a view within of both eyes. At the opposite,
and greatly enlarged, end is a screen which is rendered fluorescent
by means of a new substance (tungstate of calcium) discovered by Mr.
Edison after some eighteen hundred experiments. Such is the power of
this fluoroscope that it may be used as an independent instrument in
cases of minor surgery to locate bullets or other objects buried in the
flesh, even before a photograph has been taken. (4.) The photographic
plate, which is prepared with a sensitized film and mounted in a
frame as in ordinary photography. Upon this film the object to be
photographed is laid, say, for instance, the human hand, care being
taken to have the film or plate at a proper distance from the Crookes
tube. Current is now turned into the tube, the X ray is developed, the
film is exposed to its effects, and the result is a negative showing
the interior structure of the hand,—the bones or any foreign object
therein. This negative is developed as in ordinary photography.
The discovery and application of the X ray has proved of immense value
in medicine and surgery. By its means the physician is enabled to
carry on far-reaching diagnoses, and to ascertain with certainty the
whole internal structure of the human body. Fractures, dislocations,
deformities, and diseases of the bones may be located and their
character and treatment decided upon. In dentistry, the teeth may
be photographed by means of the X ray, even before they come to the
surface, and broken fangs and hidden fillings may be located. Foreign
objects in the body, as bullets, needles, calculi in the bladder,
etc., may be localized, and the surgery necessary for their safe
removal greatly simplified. The beating of the heart, movement of the
ribs in respiration, and outline of the liver may be exhibited to the
eye. It has been boldly suggested that in the X ray will be found an
agent capable of destroying the various bacilli which infest the human
system, and become germs of such destructive diseases as cholera,
yellow fever, typhoid fever, diphtheria, and consumption. Even if this
be speculative as yet, there is still room for marvel at the actual
results of the discovery of the X ray, and its future study opens a
field full of the grandest possibilities.
IX. OTHER ELECTRICAL WONDERS.
The novel idea of keeping time by means of electricity originated
quite early in the century, and culminated in two kinds of electric
clocks, one moved directly by the electric current, the other moved
by weights or springs, but regulated by electricity. The former have
the advantage of running a very long time without attention, but as
it is impossible to keep up an unvarying electric current, they are
not so accurate as the latter in keeping time. Though the latter are
popularly called electric clocks, they are really only clocks regulated
by electricity, and in such regulation the electric current comes to
be a most important agent, as is proved at all centres of astronomical
and other observations, as at Greenwich and Washington. At such centres
the astronomical time-keeper is set up so as to run as infallibly as
possible. This central time-keeper, say at Washington, is electrically
connected with other clocks, at observatories, signal-service stations,
railway stations, clock-stores, city halls, etc., throughout the
country. Should any of these clocks lose or gain the minutest fraction
of time as compared with that of the central time-keeper, the electric
current corrects such loss or gain, and so keeps all the clocks at a
time uniform with one another and with the central one. Electrical
devices are also often attached to individual clocks, as those upon
city hall towers and in exposed places, for the purpose of meeting
and correcting inequalities of time occasioned by weather exposure,
expansion and contraction by heat and cold, etc.
The fatherhood of the very useful and elegant arts of electrotyping
and electroplating is in dispute. Daniell, while perfecting his
battery, noticed that a current of electricity would cause a deposit
of copper. In 1831, Jacobi, of St. Petersburg, called attention to the
fact that the copper deposited on his plates of copper by galvanic
action could be removed in a perfect sheet, which presented in relief,
and most accurately, every accidental indentation on the original
plates. Following this up, he employed for his battery an engraved
copper plate, caused the deposit to be formed upon it, removed the
deposit, and found that the engraving was impressed on it in relief,
and with sufficient firmness and sharpness to enable him to print from
it. Jacobi called his discovery galvanoplasty in the publication of
his observations in 1839. It was but a step from this discovery to
the application of the electrotyping process to the art of printing.
A mould of wax, plaster, or other suitable substance is made of an
engraving or of a page of type. This mould is covered with powdered
graphite (black lead) so as to make it a conductor of electricity.
It is then inserted in a bath containing a solution of sulphate of
copper. An electric current is passed through the bath, and the copper
is deposited on the mould in sufficient quantity to give it a hard
surface capable of offering greater resistance in printing than the
types themselves, and also of producing a clearer impression. In
electroplating, practically the same principle is employed. The bath is
made to contain a solution of water, cyanide of potassium, and whatever
metal—gold, silver, platinum, etc.—it is designed to precipitate on
the article to be electroplated. The current is then passed through the
bath, and the article—spoon, knife, fork, etc.—to be electroplated
receives its coating of gold, silver, German silver, platinum, or
whatever has been made the third agent in the bath.
The various modern submarine devices for the destruction of ships,
known as torpedoes, submarine mines, etc., depend upon electricity for
their efficiency. It is the lighting or firing agent, and is carried to
the torpedo or mine by means of stout wires or cables from some safe
shore-point of observation.
In railroading, electricity has become an indispensable agent for
the operation of signal systems, opening and closing of switches,
and limitation of safety sections. It moves the drill in the mine,
sets off the blast, and supplies the light. It enables the dentist
to manipulate his most delicate tools and do his cleanest and least
painful work. In medicine it is a healing, soothing agent, boundless
in variety of application and wondrous in results. It is a stimulus
to the growth of certain plants, and has given rise to a new science
called Electro-horticulture. It may be made a prolific source of heat
for warming cars, and even for the welding of iron and steel. The
electric fan cools our parlors and offices in summer, and the electric
bell simplifies household service. In fact, it would appear that, in
contrasting the electrical beginnings with the electrical endings of
the nineteenth century, the space of a thousand rather than a hundred
years had intervened, and that in measuring the agents which conduce to
human comfort and convenience, electricity is easily the most potential.
X. ELECTRICAL LANGUAGE.
Out of the various discoveries and applications of electricity almost
a new language has sprung. This is especially so of terms expressive
of the measurements of electric energy, and of the laws governing the
application of electric power. For a time, various nations measured and
applied by means of terms chosen by themselves. This led to a jargon
very confusing to writers and investigators. It became needful to have
a language more in common, as in pharmacy, so that all nations could
understand one another, could compute alike, and especially impart
their meaning to those whose duty it became to apply discovered laws
and actual calculations to practical electric operations. This was a
difficult undertaking, owing to the tenacity with which nations clung
to their own nomenclatures and terminologies. But the drift, though
slow, finally ended at the Electrical Congress in Paris in 1881, in the
adoption of a uniform system of measurements of electric force, and an
agreement upon terms for laws and their application, which all could
understand.
Three fundamental units of measurement were first agreed upon,—the
_Centimetre_ (.394 in.) as a unit of length; the _Gramme_ (15.43
troy grains) as a unit of mass; the _Second_ (1/60 of a minute) as a
unit of time. These three units became, when referred to together
by their initial letters, the basis of the C. G. S. system of units.
Now by these units of measurement something must be measured, as, for
instance, the electric force; and when so measured, an absolute unit of
force must be the result.
DYNE:—This is but a contraction of _dynam_, force. It was adopted
as the name of the “Absolute Unit of Force,” or the C. G. S. unit of
force, and is that force which, if it act for a second on one gramme of
matter, gives to it a velocity of one centimetre per second.
AMPERE:—Electrical force produces electrical current. Current must
be measured and an absolute unit of current strength agreed upon. The
“Absolute Unit of Current” was settled as one of such strength as that
when one centimetre length of its circuit is bent into an arc of one
centimetre radius, the current in it exerts a force of one dyne on a
unit magnet-pole placed at the centre. But the absolute unit of current
as thus obtained was decided to be ten times too great for practical
purposes. So a practical unit of current was fixed upon, which is just
one tenth part of the above absolute unit of current. This practical
unit of current was called the ampere, in honor of the celebrated
French electrician, Ampère. It may be ascertained in other ways,
as when a current is of sufficient strength to deposit in a copper
electrolytic cell 1.174 grammes (18.116 grains) of copper in an hour,
such current is said to be of one ampere strength; or a current of one
ampere strength is such a one as would be given by an electro-motive
force of one volt through a wire offering one ohm of resistance.
VOLT:—This was named from Volta, the celebrated Italian electrician,
and was agreed upon as the unit of electro-motive force. It is that
electro-motive force which would be generated by a conductor cutting
across 100,000,000 C. G. S. lines in a field of force per second; or it
is that electro-motive force which would carry one ampere of current
against one ohm of resistance.
OHM:—So called from Ohm, a German electrician. It is the unit of
resistance offered by a conductor to the passage of an electrical
current. As an absolute unit of resistance, it is equal to
1,000,000,000 C. G. S. units of resistance. As a practical unit, and
as agreed upon at the International Congress of Electricians (Chicago,
1893), it represents the resistance offered to an electric current at
the temperature of melting ice by a column of mercury 14.451 grammes
in mass, of a constant cross-sectional area, and 106.3 centimetres in
length. This is called the international ohm. The resistance offered by
400 feet of ordinary telegraph wire is about an ohm.
These three units—ampere, volt, and ohm—are the factors in
Ohm’s famous law that the current is directly proportional to the
electro-motive force exerted in a circuit, and inversely proportional
to the resistance of the circuit; that is,—
Current = Electro-motive force / Resistance
or,
Electro-motive force = Current × Resistance
or
Resistance = Electro-motive force / Current.
ERG:—From the Greek _ergon_, work, is the unit of work required to
move a force of one dyne one centimetre. One foot-pound equals 13,560
ergs.
CALORIE:—Latin _calor_, heat, is the unit of heat; being the amount
of heat required to raise the temperature of one kilogram of water one
degree centigrade.
COULOMB:—In honor of C. A. de Coulomb, of France. It is the practical
unit of quantity in measuring electricity, and is the amount conveyed
by one ampere in one second.
FARAD:—From FARADAY, the physicist. It is the unit of electric
capacity, and is the capacity of a condenser that retains one coulomb
of charge with one volt difference of potential.
GAUSS:—From Carl F. Gauss (1785–1855). The C. G. S. unit of
flux-density, or the unit by which the intensity of magnetic fields are
measured. It equals one weber per normal square centimetre.
GILBERT:—The unit for measuring magneto-motive force, being produced
by .7958 ampere-turn approximately.
HENRY:—From Joseph Henry, of the Smithsonian Institution, Washington,
D. C. The practical unit for measuring the induction in a circuit when
the electro-motive force induced is one international volt, while the
inducing current varies at the rate of one ampere per second.
JOULE:—The C. G. S. unit of practical energy, being equivalent to the
work done in keeping up for one second a current of one ampere against
a resistance of one ohm. Named from J. P. Joule, of England.
OERSTED:—From Oersted, the electrician. It is the practical unit for
measuring electrical reluctance.
WATT:—The practical electrical unit of the rate of working in a
circuit, when the electro-motive force is one volt, and the intensity
of current is one ampere. It is equal to 107 ergs per second, or .00134
horse-power per second. Named from James Watt, of Scotland.
WEBER:—The practical unit for measuring magnetic flux. Named from W.
Weber, of Germany.
THE CENTURY’S NAVAL PROGRESS
BY REAR ADMIRAL GEORGE WALLACE MELVILLE, U. S. N.
I. INFLUENCE OF SEA POWER.
The share of navies in the great movements which have moulded human
destiny and shaped the world’s progress, although long obscure and
undervalued, has met in our time full recognition. Within a decade the
influence of sea power upon history has become the frequent theme of
historians and essayists who, in clear and striking form, have shown
the cardinal importance, both in war and commerce, of the fleet—the
nation’s right arm on the sea. It is fitting, therefore, that in the
retrospect of a hundred years navies should have their place; that, in
looking backward with history’s unclouded vision, we should mark, not
only their growth and change, but, as well, their achievement in some
of the most memorable conflicts of our race.
The century had but begun when, at Copenhagen, Nelson, with one titanic
blow, shattered the naval strength of Denmark and the coalition of the
Northern powers. His signal there, ever for “closer battle,” told in
few words the life story of the Great Admiral, and foreshadowed his
end. Four years later, at Trafalgar, the desire of his eager heart
was satisfied, when he met in frank fight the fleets of France and
Spain. Amid the thundering cannonade of that last victory his life-tide
ebbed, bearing with it the power of France upon the seas and the broken
fortunes of Napoleon. In the war of 1812, our disasters upon the land
met compensation in victory afloat. The United States was then among
the feeblest of maritime powers; and yet Macdonough and Perry on the
lakes and our few frigates on the ocean opposed, with success, the
swarming squadrons of a nation whose naval glory, as Hallam says, can
be traced onward “in a continuous track of light” from the days of the
Commonwealth. The oppression of the Sultan was ended for a time when,
in 1827, the Turkish and Egyptian fleets were annihilated, in sudden
fury, by the allied squadrons in that brief engagement which Wellington
termed the “untoward event” of Navarino.
A generation later, the command of the sea enabled England and France
to despatch, in unarmed transports, 63,000 men and 128 guns to the
Crimea, and to land them, without opposition, for the red carnage of
the Alma, Balaklava, Inkerman, and Sebastopol. Following closely upon
the disease and death, the fatuity and the glory, of the Crimea, came
the great war of modern times, in which the gun afloat played such a
gallant part, as the blockade, with its constricting coils, slowly
starved and strangled the Confederacy to death, and Farragut, on inland
waters, split it in twain. Passing over the sea-fights of Lissa,—in
which imperial Venice was the stake,—of South America and the Yalu, we
note, lastly, the swift and fateful actions off Santiago and in Manila
Bay, which destroyed once again the sea power of Spain, won distant
territory for the United States, and opened up for us a noble pathway
of commercial expansion to the uttermost island of the broad Pacific
and the vast Asian littoral beyond. Who will say, in the retrospect of
the century, that the fleets of the world have not had their full share
in the making of its history?
II. THE CENTURY’S GROWTH IN NAVAL STRENGTH.
The United States fleet, in the year 1800, comprised 35 vessels, 10 of
which were frigates mounting 32 guns or more. In 1812, America entered
the lists against a navy of a thousand sail, with a fleet of but 20
ships, the largest of which was a 44-gun frigate. The operations of
the Civil War were begun with but 82 vessels, 48 of which were sailing
craft. Before the close of that gigantic struggle there were added,
by construction or purchase, 674 steamers. In 1898, during the war
with Spain, there were borne on the Naval Register, as building or
in service, 13 battleships and 176 other vessels, including torpedo
craft, with 123 converted merchantmen. The total naval force during
hostilities was 22,832 men and 2382 officers, excluding the Marine
Corps.
[Illustration: AN AUGUST MORNING WITH FARRAGUT.
(Battle of Mobile Bay.)]
At London, in 1653, there was printed “A List of the Commonwealth
of England’s Navy at Sea, in their expedition in May, 1653, under
the command of the Right Honorable Colonel Richard Deane and Colonel
George Monk, Esquires, Generals, and Admirals.” This quaint record of
that early time gives the force afloat as 105 ships, 3840 guns, and
16,269 men. In Britain’s strife for that ocean empire, which is world
empire, that fleet had grown, by the year 1800, to 757 vessels, built
or building, with an aggregate tonnage of 629,211, and carrying 26,552
guns, 3653 officers, and 110,000 men. The stately three-decker, with
its snowy canvas and maze of rigging, has vanished with the past; but,
despite time and change, that mighty fleet still dominates the seas.
Its strength, on February 1, 1898, was 615 vessels—61 of which were
battleships,—carrying a total force of 110,050 officers and men.
[Illustration: BRITISH BATTLESHIP MAJESTIC.]
[Illustration: FRENCH BATTLESHIP MAGENTA.]
Colbert, when the Grand Monarch was at the zenith of his power, found
France with a few old and rotten vessels, and left her with a noble
fleet of 40 ships of the line and 60 frigates, which, under D’Estrée,
Jean Bart, Tourville, and Duquesne, carried her flag to every sea.
A state paper of the time gives the force at the beginning of this
century as 61 ships of the line, 42 corvettes, and a numerous, although
unimportant, flotilla of small craft. With Aboukir and Trafalgar, the
maritime power of France wasted away; and, by the year 1839, there
were afloat but three effective sail of the line. In 1840, however,
the revival began, and during the modern era the French fleet has,
at times, been a formidable rival of that of England. It comprised,
in 1898, 446 vessels, including torpedo craft, 26 of the total being
battleships. The force afloat numbered 70,925, of all ranks and ratings.
[Illustration: GERMAN BATTLESHIP WOERTH.]