ELECTRICITY AND RADIOACTIVITIES
Among the most marvelous scientific developments of the nineteenth
century those in the electrical field claim universal attention. It was
only as recently as 1844 that Morse introduced electric telegraphy. The
telephone was introduced by Alexander Graham Bell in 1876 and Edison
built one of his early dynamos in 1878 and in 1879 made his first high
resistance incandescent lamp for parallel operation. The first Edison
power and lighting station was opened at 257 Pearl Street, New York
City, in 1882.
Although electrical phenomena were understood in a general way
thousands of years ago, they were not studied and applied to practical
purposes until the sixteenth century when William Gilbert carried out
his classical experiments in the reign of Queen Elizabeth. The Leyden
jar was discovered in the early half of the eighteenth century. From
experiments carried out with these jars a great number of important
inventions were derived and our knowledge of electricity was for many
years dependent upon researches of this kind. Benjamin Franklin in
experimenting with the Leyden jar found that its electrical discharges
were similar to those of lightning and he subsequently discovered that
the inner part of the jar, when charged with a frictional current, was
positively electrical while the outer portion was negative.
The voltaic pile was invented in 1796 as a result of Galvani's
experiments in physiological electricity and Sir Humphry Davy exhibited
the first practical electrical lamp before the Royal Society in 1809.
The dynamo was, in substance, invented by Faraday, and described by
him before the Royal Society in 1831. This was, perhaps, the greatest
of all electrical triumphs because it gave engineers a practical means
of generating and using electrical currents of any desired dimensions.
Bunsen in 1840 devised a means for making carbon rods for arc lamps,
and Edison made practical carbon incandescent lamp filaments in 1879.
Faraday's invention promoted all of these lighting discoveries.
The engine-driven electric dynamo was made a practical machine in 1870
and thenceforward became the source of power of a great multitude of
secondary machines, such as electric street cars, marine engines, power
plants, and forging hammers.
A new and profitable field was opened for the use of electricity by
the invention of the electric furnace. Sir Humphry Davy produced
his electric arc in 1808 and was greatly impressed with its fusing
properties. He melted many metals with the arc and found that it fused
platinum just as easily as an ordinary tallow candle melts beeswax.
The electric furnace, which is now extensively used in chemical and
metallurgical works, is simply a large electric arc provided with means
for containing the heat. Furnaces lined with carbon are now heated to
over 4,000 degrees centigrade.
When the electrical manufacture of aluminum on a large scale was
started at Niagara, Dr. Edward Acheson, who was impressed by the
industrial needs of cheap abrasives, accidentally discovered that by
heating a piece of porcelain to a high temperature in an electric
furnace and bringing it in contact with pure carbon, the carbon was
rendered very hard. In 1891 he carried on experiments with high
currents and a mixture of ground coke and sand. He found a method of
fusing these so that the oxygen of the sand passed off with carbon
in the form of carbonic acid gas, and the reduced metallic silicon
combined with an equal atomic weight of carbon and produced a new body
which he named carborundum. The success met with in making carborundum
led to the devising of a method of manufacturing artificial graphite in
the electric furnace. A soft, non-coalescing graphite was made in 1906.
This is extensively used in lubricating heavy machinery.
Dr. Acheson produced the first chemically pure artificial carbon in his
electric furnace in 1911. By using pressure during consolidation this
carbon may eventually be converted into diamonds.
Another valuable product of the electric furnace, acetylene gas, was
discovered in Dublin by Edmund Davy in 1836. Subsequently numerous
chemists discovered means for making carbides. T. Sterry Hunt, an
American chemist, observed in 1886 that oxides of the alkaline metals
and of calcium, magnesium, aluminum, silicon, and boron could be
reduced in the electric furnace in the presence of carbon and could be
alloyed with other metals. He also found that silicon and acetylene
could be made that way.
T. L. Wilson, a Canadian engineer, in attempting to make aluminum
bronze in an electric furnace, devised an experiment for reducing lime
with carbon. He found that this produced calcium carbide and secured a
patent for the invention in 1892. Variations of this process are now
used for manufacturing nitrogen and nitrates from atmospheric nitrogen.
Wireless developments have resulted from the work of many separate
investigators. K. A. Steenheil in 1838 used the earth return in live
telegraphy and suggested the possibility of wireless telegraphy.
Joseph Henry produced the first high-frequency oscillations in America
in 1840. Lord Kelvin in 1853 enunciated the mathematical principles
governing uncoupled electrical oscillatory circuits. Joseph Heyworth
patented a wireless telegraphic process in 1862. Clark Maxwell in 1867
predicted the existence of electromagnetic radiations and these were
demonstrated by Hertz in 1887. Hughes discovered the phenomena of the
coherer and Branby used Hughes's coherer for wireless wave detection
in 1892. A. E. Dolbear secured United States patents for a system of
wireless telegraphy using aerials in 1886. Sir Oliver Lodge described
his wireless system before the Royal Society in 1894 and in the same
year Popoff issued descriptions of his wireless system.
Wireless telegraphy became commercially practicable in 1897 when G.
Marconi secured the promotion of the Wireless Telegraph and Signal
Company in England. Marconi succeeded in turning to commercial account
a long series of brilliant discoveries in electricity, and this success
has led to numerous kindred discoveries. De Forest's three-electrode
thermionic detector, known as an Audion, invented in 1907 and improved
in 1911 by Lieben and Reiss, in 1913 by Meisser and in 1914 by
Langmuir, opened up great possibilities for sound transmission by
wireless telephony.
The electric deposition and refining of metals have been referred to
in previous chapters. Many industries are based upon these. Niepce
produced commercially successful photographs in 1838. Earlier, in
1824, he had etched plates for printing and in that year published his
photo-engraving of Cardinal d'Amboise. Fox Talbot patented a mixture
of gelatine and bichromate of potash to take the place of the bitumen
used by Niepce as a plate coating. Gillot found in 1872 that Fox
Talbot's method of making intaglio plates could also be used for making
relief blocks. In 1885-1886, F. E. Ives sealed two single-line screws
together and made a new fine cross-line screen, which resulted in the
development of the half-tone process. Ives at this time also developed
the three-color photo-engraving process.
Photography and photo-engraving are so widely used and are so
intimately connected with our civilization that few people now realize
that the great industries based upon them are the results of a few
scientific discoveries of a couple of American and European scientists
made only a generation or two ago.
[Illustration: GIFTS FOR TUTANKHAMEN BROUGHT BY HUY, VICEROY OF
ETHIOPIA. THE MAN IN THE GAY COSTUME, AT THE RIGHT, MAY BE A PHŒNICIAN.
(EGYPTIAN PAINTING)]
[Illustration: TUTANKHAMEN'S TOMB--BRINGING UP THE HATHOR COUCH. THE
COW WAS SACRED TO ISIS OR HATHOR OF WHOM THE HORNS WITH THE MOON DISK
WERE EMBLEMS]
[Illustration: QUEEN NEFERTITI, MOTHER-IN-LAW OF TUTANKHAMEN
This wonderful work of an unknown Egyptian sculptor represents the
wife of Ahknaton, the "heretic" king of Egypt (originally Amenhotep or
Amenophis IV). The original is now in the Berlin Museum.]
Chemists had long recognized the fact that certain chemicals like
preparations of zinc, fluorine, and phosphorus were phosphorescent. It
was found early in the eighties that Welsbach gas mantles, when placed
on a photographic plate and exposed in a dark room for two weeks,
made a fine picture. Invisible rays in the mantle imprint its image.
Röntgen, in 1895, discovered what are now known as the X-rays. This
discovery was the result of experiments begun in 1859 by Plucker to
ascertain the cause of fluorescence in light glass, and Sir William
Crookes, between 1879 and 1885, carried out beautiful experiments on
fluorescence. These were the immediate pioneers of the discovery of the
cathode rays and the other great radio discoveries of recent years.
Crookes, remembering Faraday's suggestions concerning a fourth state of
matter, expressed the opinion, in 1885, that the matter constituting
cathode rays is neither solid, gaseous, or liquid, but in a fourth
state which transcends the gaseous condition. Perren found in 1895 that
the rays carried electrically negative charges and Sir J. J. Thomson
noticed that their velocities are appreciably less than the speed of
light. Owing, however, to their great momentum, hardly anything can
long endure their impacts. They fuse platinum and make diamonds buckle
up into coke.
Electrons, which constitute the cathode rays, were originally studied
in Crookes vacuum tubes, though they are now found to pervade the
universe.
Larmor in 1897 proposed an electronic theory of magnetism.
Henri Becquerel was the first to discover radioactivity. He made
radiographs from uranium salts in 1896. M. and Madame Curie undertook
the investigation of uranium and found that among the minerals
occurring in pitchblende, or uranium ore, bismuth and barium showed
radioactive properties, whereas when these metals are found in their
ordinary ores they are not radioactive. This discovery led to the
finding of two new metals, polonium and radium. Radium is now obtained
by fractional distillation of solutions obtained from American and
Australian pitchblende.
Helium, one of the lightest substances known, was discovered in 1895
by Sir William Ramsay, and liquefied, at a temperature 3 degrees above
absolute zero, or -270 degrees centigrade, by Onnes in 1908. Helium
appears to be one of the ultimate products of the disintegration of all
radioactive elements.
Some of the most interesting discoveries about radioactivity are very
recent. Radium prepared from uranium in 1915 was found in 1919 to have
increased proportionately to the square of the time interval. The
amount of radium in some preparations was found to have increased ten
times in four years. The old idea of the constant fluxation of matter
was thus shown to have been based upon a scientific truth.