the world how to obtain.

Faraday lived to see his infant dynamo, the first of its kind, developed
into a machine not only sufficiently powerful to maintain electric arc
lights, but also into a form sufficiently practicable to be continuously
engaged in producing such light, in one of the lighthouses on the
English coast. Holmes produced such a machine in 1862, or some years
before Faraday's death. It was installed under the care of the Trinity
House, at the Dungeness Lighthouse, in June, 1862, and continued in use
for about ten years. When this machine was shown to Faraday by its
inventor, the veteran philosopher remarked, "I gave you a baby, and you
bring me a giant."

The alternating-current transformer is another gift of Faraday to the
commercial world. As is well known, this instrument is a device for
raising or lowering electric pressure. The name is derived from the fact
that the instrument is capable of taking in at one pressure the electric
energy supplied to it, and giving it out at another pressure, thus
transforming it. Faraday produced the first transformer during his
investigations on voltaic-current induction. The modern
alternating-current transformer, though differing markedly in minor
details from Faraday's primitive instrument, yet in general details is
essentially identical with it. The enormous use of both step-up and
step-down transformers--transformers which respectively induce currents
of higher and of lower electromotive forces in their secondary coils
than are passed through their primaries--shows the great practical value
of this invention. The wonderful growth of the commercial applications
of alternating currents during the past few decades would have been
impossible without the use of the alternating-current transformer.

It is an interesting fact that it was not in the form of the step-down
alternating-current transformer that Faraday's discovery of
voltaic-current induction was first utilized, but in the form of a
step-up transformer, or what was then ordinarily called an induction
coil. As early as 1842, Masson and Breguet constructed an induction
coil by means of which minute sparks could be obtained from the
secondary, in vacuo. In 1851, Ruhmkorff constructed an induction coil so
greatly improved, by the careful insulation of its secondary circuit,
that he could obtain from it torrents of long sparks in ordinary air.
The Ruhmkorff induction coil has in late years been greatly improv