born at Edinburgh on November 13, 1831, and before
he was fifteen was already famous as a writer of scientific papers.
In 1854 he graduated at Cambridge as second wrangler. Two years
later he became professor of natural philosophy at Marischal
College, Aberdeen. Vacating his chair in 1860 for one at King's
College, London, Maxwell contributed largely to scientific
literature. His great lifework, however, is his famous "Treatise on
Electricity and Magnetism," which was published in 1873, and is, in
the words of a critic, "one of the most splendid monuments ever
raised by the genius of a single individual." It was in this work
that he constructed his famous theory if electricity in which
"action at a distance" should be replaced by "action through a
medium," and first enunciated the principles of an electro-magnetic
theory of light which has formed the basis of nearly all modern
physical science. He died on November 5, 1879.

_I.--The Nature of Electricity_

Let a piece of glass and a piece of resin be rubbed together. They will
be found to attract each other. If a second piece of glass be rubbed
with a second piece of resin, it will be found that the two pieces of
glass repel each other and that the two pieces of resin are also
repelled from one another, while each piece of glass attracts each piece
of resin. These phenomena of attraction and repulsion are called
electrical phenomena, and the bodies which exhibit them are said to be
"electrified," or to be "charged with electricity."

Bodies may be electrified in many other ways, as well as by friction.
When bodies not previously electrified are observed to be acted on by an
electrified body, it is because they have become "electrified by
induction." If a metal vessel be electrified by induction, and a second
metallic body be suspended by silk threads near it, and a metal wire be
brought to touch simultaneously the electrified body and the second
body, this latter body will be found to be electrified. Electricity has
been transferred from one body to the other by means of the wire.

There are many other manifestations of electricity, all of which have
been more or less studied, and they lead to the formation of theories of
its nature, theories which fit in, to a greater or less extent, with the
observed facts. The electrification of a body is a physical quantity
capable of measurement, and two or