bersome. Faure improved it somewhat
by coating the lead plates with red-lead, thus increasing the capacity
of the cell. Faure's invention gave a fresh impetus to inventors, and
shortly after the market was filled with storage batteries of various
kinds, most of them modifications of Planche's or Faure's. The ardor
of enthusiastic inventors soon flagged, however, for all these storage
batteries proved of little practical account in the end, as compared
with other known methods of generating power.

Three methods of generating electricity are in general use: static or
frictional electricity is generated by "plate" or "static" machines;
galvanic, generated by batteries based on Volta's discovery; and
induced, or faradic, generated either by chemical or mechanical action.
There is still another kind, thermo-electricity, that may be generated
in a most simple manner. In 1821 Seebecle, of Berlin, discovered that
when a circuit was formed of two wires of different metals, if there
be a difference in temperature at the juncture of these two metals
an electrical current will be established. In this way heat may
be transmitted directly into the energy of the current without the
interposition of the steam-engine. Batteries constructed in this way
are of low resistance, however, although by arranging several of them
in "series," currents of considerable strength can be generated. As yet,
however, they are of little practical importance.

About the middle of the century Clerk-Maxwell advanced the idea that
light waves were really electro-magnetic waves. If this were true and
light proved to be simply one form of electrical energy, then the same
would be true of radiant heat. Maxwell advanced this theory, but failed
to substantiate it by experimental confirmation. But Dr. Heinrich
Hertz, a few years later, by a series of experiments, demonstrated the
correctness of Maxwell's surmises. What are now called "Hertzian waves"
are waves apparently identical with light waves, but of much lower
pitch or period. In his experiments Hertz showed that, under proper
conditions, electric sparks between polished balls were attended by
ether waves of the same nature as those of light, but of a pitch of
several millions of vibrations per second. These waves could be dealt
with as if they were light waves--reflected, refracted, and polarized.
These are the waves that are utilized in wireless telegraphy.

ROENTGEN RAYS, OR X-RAYS

In December of