e radiation has
been reduced to three-quarters, or 75 units; hence, the effect of the
lessening of the radiation is to raise the temperature of each remaining
inch not radiating to 125 degrees. If the radiating surface should be
reduced to three-thirty-seconds of an inch, the temperature would reach
6400 degrees Fahr. To carry out this law to the best advantage in regard
to platina, etc., then with a given length of wire to quadruple the heat
we must lessen the radiating surface to one-quarter, and to do this in a
spiral, three-quarters must be within the spiral and one-quarter outside
for radiating; hence, a square wire or other means, such as a spiral
within a spiral, must be used. These results account for the enormous
temperature of the Electric Arc with one horse-power; as, for instance,
if one horse-power will heat twelve inches of wire to 1000 degrees
Fahr., and this is concentrated to have one-quarter of the radiating
surface, it would reach a temperature of 4000 degrees or sufficient
to melt it; but, supposing it infusible, the further concentration to
one-eighth its surface, it would reach a temperature of 16,000 degrees,
and to one-thirty-second its surface, which would be about the radiating
surface of the Electric Arc, it would reach 64,000 degrees Fahr. Of
course, when Light is radiated in great quantities not quite these
temperatures would be reached.

"Another curious law is this: It will require a greater initial battery
to bring an iron wire of the same size and resistance to a given
temperature than it will a platina wire in proportion to their specific
heats, and in the case of Carbon, a piece of Carbon three inches long
and one-eighth diameter, with a resistance of 1 ohm, will require a
greater battery power to bring it to a given temperature than a cylinder
of thin platina foil of the same length, diameter, and resistance,
because the specific heat of Carbon is many times greater; besides, if
I am not mistaken, the radiation of a roughened body for heat is greater
than a polished one like platina."

Proceeding logically upon these lines of thought and following them
out through many ramifications, we have seen how he at length made a
filament of carbon of high resistance and small radiating surface, and
through a concurrent investigation of the phenomena of high vacua and
occluded gases was able to produce a true incandescent lamp. Not only
was it a lamp as a mere article--a device to give light--