force from the same amount of material, the advantage being chiefly
due to the large increase of magnetic intensity in the field magnets.
At this period lights of enormous power were produced with ease and by
the use of costly lamps. With complicated mechanism a new era in
artificial illumination seemed close at hand, but a grave difficulty
stood in the way--namely, the proper distribution or subdivision of
the light. It was quickly found that the electric difficulty of
subdividing the light, added to the great cost of the lamps then made,
was an apparently insurmountable obstacle to its general adoption, and
the electric light was gradually taking its place as a brilliant
scientific toy, when the world was startled by the introduction of the
Jablochkoff candle, which may fairly claim to have given a greater
impetus to the new light than any previous invention, a stimulus
without which it is even probable that electric lighting might have
slumbered for another decade.

The Jablochkoff candle embodies a very beautiful philosophical
principle, and though its promises have not been fulfilled in general
practice, we must not forget that we owe it much for arousing
scientific men from a dangerous lethargy.

Up to this time the light had always been produced by approximation of
carbon rods with their axes in the same plane; but the Jablochkoff
candle consisted of like rods arranged parallel to each other and
about one-eighth of an inch apart, the intervening space being filled
with plaster of Paris, and the interval at the top bridged by a
conducting medium. The object of the plaster, which is a fairly good
insulating material at ordinary temperatures, is to prevent the
passage of the current except at the top, where the conducting
material just referred to assisted the formation of the arc at that