In no other department of physical science have such remarkable
developments occurred during the past century as in electricity and
magnetism, for in no other department have the practical applications
of scientific discovery been so numerous and so far reaching in their
effect upon social conditions. In a brief review of the contributions
of the nineteenth century to the evolution of the telegraph, telephone,
trolley-car, electric lighting, and other means of utilizing
electricity, it will be possible to consider only a very few of the
fundamental discoveries upon which the enormous and rather complex
superstructure of to-day rests. Happily these are few in number, and
their presentation is all the more important because of the fact that
in the popular mind they are not accorded that significance to which
they are entitled, if, indeed, they are remembered at all.
The first great step in advance of the electricity of Franklin and his
contemporaries (and his predecessors for two thousand years) was taken
very near the end of the eighteenth century, but it must be regarded
as the beginning of nineteenth-century electricity. Two Italian
philosophers, Galvani and Volta, contributed to the invention of what
is known as the galvanic or voltaic battery, the output of which was
not at first distinctly recognized as the electricity of the older
schools. By this beautiful discovery electricity was for the first time
enslaved to man, who was now able to generate and control it at times
and in such quantities as he desired. Although the voltaic battery is
now nearly obsolete as a source of electricity, its invention must
always be regarded as one of the three epoch-making events in the
history of the science during the past one hundred and twenty years.
For three-quarters of a century it was practically the only source of
electricity, and during this time and by its use nearly all of the
most important discoveries were made. Even in the first decade of the
century many brilliant results were reached. Among the most notable
were the researches of Sir Humphry Davy, who, by the use of the most
powerful battery then constructed, resolved the hitherto unyielding
alkalies, discovering sodium and potassium, and at the same time
exhibited in his lectures in the Royal Institution in London the first
electric arc light, the ancestor of the millions that now turn night
into day.
The cost of generating electricity by means of a voltaic battery is
relatively very great, and this fact stood in the way of the early
development of its applications, although their feasibility was
perfectly well understood. Without any other important invention or
discovery than that of the voltaic battery much would have been
possible, including both electric lighting and the electric telegraph.
Indeed, electric telegraphy had long been a _possibility_, even before
the time of Galvani and Volta, but its actual construction and use was
almost necessarily postponed until a second capital discovery came to
remove most of the difficulties.
This was the discovery of a relation between electricity and magnetism,
the existence of which had long been suspected and earnestly sought.
A Danish professor, Hans Christian Oersted, was fortunate in hitting
upon an experiment which demonstrated this relation and opened up an
entirely new field of investigation and invention. What Oersted found
was that when a conductor, as a copper wire, carrying an electric
current, was brought near a freely suspended magnet, like a compass
needle, the latter would take up a definite position with reference
to the current. Thus an electric current moved a magnet, acted like a
magnet in producing a “magnetic field.” The subject was quickly taken
up by almost every physicist in Europe and America. Arago found that
iron filings would cling to a wire through which a current was passing,
and he was able to magnetize steel needles by means of the current.
Ampère, another French physicist, studied Oersted’s wonderful discovery
both experimentally and mathematically, and in an incredibly short time
so developed it as to deserve the title of creator of the science of
electro-dynamics.
The first to make what is known as an electro-magnet was an Englishman
named Sturgeon, who used a bar of soft iron bent in a horseshoe form
(as had long been common in making permanent steel magnets), and,
after varnishing the iron for insulation, a single coil of copper
wire was wrapped about it, through which the current from a battery
was passed. There were thus two ways of producing visible motion by
means of an electric current: that of Oersted’s simple experiment,
in which a suspended magnetic needle was deflected by a current, and
that made possible by the production, at will, of an electro-magnet.
The application of both of these ideas to the construction of an
electric telegraph was quickly attempted, and two different systems of
telegraphy grew out of them. One, depending on Oersted’s experiment,
was developed in England first and afterwards in Europe; the other,
that involving the use of signals produced by an electric magnet, was
developed in America, and was generally known as the American method.
It has long ago superseded the first method in actual practice. Its
possibility depended on perfecting the electro-magnet and especially
on an understanding of the principles on which that perfecting
depended. For the complete and satisfactory solution of this problem
we are indebted to the most famous student of electricity America has
produced during the century, Joseph Henry. In 1829, while a teacher in
the academy at Albany, New York, Henry exhibited an electro-magnet of
enormously greater power than any before made, involving all of the
essential features of the magnet of to-day. The wire was insulated
by silk wrapping, and many coils were placed upon the iron core, the
intensity of magnetization being thus multiplied. Henry studied, also,
the best form and arrangement of the battery under varying conditions
of the conductor. An electro-magnetic telegraph had been declared
impossible in 1825, by Barlow, an Englishman, who pointed out the
apparently fatal fact that the resistance offered to the current was
proportional to the length of the conducting wire and that the strength
of the current would be thus so much reduced for even short distances
as to become too feeble to be detected. Henry showed that what is known
as an “intensity battery” would overcome this difficulty, discovering
experimentally and independently the beautifully simple law showing
the relation of current to electro-motive force which Ohm had announced
in 1827. He also invented the principle of the relay, by which the
action of a very feeble current controls the operation of a more
powerful local system. It will thus be seen that the essential features
of the so-called American system of telegraphy are to be credited to
Henry, who had a working line in his laboratory as early as 1832.
Morse made use of the scientific discoveries and inventions of Henry,
and by his indefatigable labors and persistent faith the commercial
value of the enterprise was really established. In the mean time
considerable progress was made in Europe. Baron Schilling, a Russian
Councillor of State, devised and exhibited a needle telegraph. The
two illustrious German physicists, Gauss and Weber, established a
successfully working line two or three miles long in 1833, and this
system was commercially developed by Steinheil in 1837. In England, Sir
Charles Wheatstone made many important contributions, although using
the needle system, which was afterwards abandoned. Before the middle of
the century the commercial success of the electro-magnetic telegraph
was assured, and in the matter of the transmission of messages distance
was practically annihilated.
Oersted, Arago, Ampère, Sturgeon, and Henry had made it possible to
convert electricity into mechanical energy. Motors of various types
had been invented, and the possibility of using the new source of
power for running machinery, cars, boats, etc., was fully recognized.
Several attempts had been made to do these things, but the great
cost of producing the current by means of a battery stood in the way
of success. Another epoch-making discovery was necessary, namely, a
method of reversing the process and converting mechanical energy
into electricity. This was supplied by the genius of Michael Faraday,
who had succeeded Davy in the Royal Institution at London. In 1831
Faraday discovered _induction_, the key to the modern development of
electricity. He showed that while Oersted had proved that a current of
electricity would generate a magnetic field and set a magnet in motion,
this process was reversible. A magnet set in motion in a magnetic
field by a steam-engine or any other source of power would produce,
in a conductor properly arranged, a current of electricity, and thus
the dynamo came into existence. In this brilliant investigation he was
almost anticipated by Henry, who was working at Albany along the same
lines, but under much less favorable conditions. Indeed, in several of
the most important points, the American actually did anticipate the
Englishman. Nearly half a century elapsed before this most important
discovery was sufficiently developed to become commercially valuable,
and it is impossible in this place to trace the steps by which, during
the last quarter of a century, the production and utilization of
electricity as existing to-day was accomplished, as a result of which
the century closed, as one might say, in a blaze of light; and it is
unnecessary, because most people have witnessed the spread of the fire
which Faraday and Henry kindled.
Faraday’s discovery of induction furnished the basis of that marvellous
improvement upon the telegraph by which actual speech is transmitted
over hundreds and even thousands of miles. In connection with the
invention of the telephone the names of Philip Reiss, Graham Bell,
Elisha Gray, and Dolbear will always be mentioned, each of whom,
doubtless independently, hit upon a way of accomplishing the result
with more or less success. To Bell, however, belongs the honor of
having first practically solved the problem and of devising a system
which, with numerous modifications and improvements, has come into
extensive use in all parts of the world. No other application of
electricity has come into such universal use, and none has contributed
more to the comfort of life.
While it is doubtless true that since Faraday’s time no discovery
comparable with his in real importance has been made, the past
twenty-five years have not lacked in results of scientific research,
some of which may, in the not distant future, eclipse even that in the
value of their practical applications. Among these must be ranked Clerk
Maxwell’s theory of electric waves and its beautiful verification in
1888 by the young German physicist, Hertz. This brilliant student of
electricity succeeded in actually producing, detecting, and controlling
these waves, and out of this discovery has come the “wireless
telegraphy” which has been so rapidly developed within the last few
years. Many other discoveries in electricity of great scientific
interest and practical promise have been recorded in the closing years
of the century, but the necessary limits of this article forbid their
consideration.
No account of the progress of physical science during the nineteenth
century would be even approximately complete without mention of other
investigations of profound significance. For instance, the study of
the phenomena of sound has yielded results of great scientific and
some practical value. The application of the theory of interference
by Thomas Young; the publication of Helmholtz’s great work, the
_Tonempfindungen_, in which his theory of harmony was first fully
presented; the publication of Lord Rayleigh’s treatise; the invention
and construction by König of acoustic apparatus, the best example
yet furnished of scientific handicraft; all of these mark important
advances, not only in acoustics but in general physics as well. The
phonautograph of Scott and König, by which a graphic record of the
vibrations of the vocal chords was made possible, was ingeniously
converted by Edison into a speech recording and reproducing machine,
the phonograph, by which the most marvellous results are accomplished
in the simplest possible manner.
The century is also to be credited with the discovery and development
of the art of photography, which, although not of the first importance,
has contributed much to the pleasure of life, and as an aid to
scientific investigation has become quite indispensable.
The wonderfully beautiful experiments of Sir William Crookes, on the
passage of an electric discharge through a high vacuum, and other
phenomena connected with what has been called “radiant matter,” begun
about a quarter of a century ago and continued by him and others up to
the present time, laid the foundation for the brilliant work of Röntgen
in the discovery and study of the so-called “X”-rays, the real nature
of which is not yet understood. Their further investigation by J. J.
Thomson, Becquerel, and others, seems to have revealed new forms and
phases of radiation, a fuller knowledge of which is likely to throw
much light on obscure problems relating to the nature of matter.
Concerning the “Nature of Matter,” the ablest physicists of the century
have thought and written much, and doubtless our present knowledge
of the subject is much more nearly the truth than that of a hundred
years ago. The molecular theory of gases has met with such complete
experimental verification, and is so in accord with all observed
phenomena, that it must be accepted as essentially correct. As to
the ultimate nature of what is called matter, as distinguished from
the ethereal medium, what is known as the “vortex theory of atoms”
has received the most consideration. This theory was developed by
Lord Kelvin out of Helmholtz’s mathematical demonstration of the
indestructibility of a vortex ring when once formed in a medium
possessing the properties which are generally attributed to the ether.
Perhaps the most remarkable as well as the most promising fact relating
to physical science at the close of the nineteenth century is the
great and rapidly increasing number of well-organized and splendidly
equipped laboratories in which original research is systematically
planned and carried out. When one reflects that for the most part
during the century just ended the advance of science was more or less
of the nature of a guerrilla warfare against ignorance, it seems safe
to predict for that just beginning victories more glorious than any yet
won.