d revolutionized in
its interior illumination. It was a triumphant vindication of Edison's
reasoning powers, his clear perceptions, his insight into possibilities,
and his inventive faculty, all of which had already been productive of
so many startling, practical, and epoch-making inventions. And now he
had stepped over the threshold of a new art which has since become so
world-wide in its application as to be an integral part of modern human
experience. [9]

[Footnote 9: The following extract from Walker on Patents
(4th edition) will probably be of interest to the reader:

"Sec. 31a. A meritorious exception, to the rule of the last
section, is involved in the adjudicated validity of the
Edison incandescent-light patent. The carbon filament, which
constitutes the only new part of the combination of the
second claim of that patent, differs from the earlier carbon
burners of Sawyer and Man, only in having a diameter of one-
sixty-fourth of an inch or less, whereas the burners of
Sawyer and Man had a diameter of one-thirty-second of an
inch or more. But that reduction of one-half in diameter
increased the resistance of the burner FOURFOLD, and reduced
its radiating surface TWOFOLD, and thus increased eightfold,
its ratio of resistance to radiating surface. That eightfold
increase of proportion enabled the resistance of the
conductor of electricity from the generator to the burner to
be increased eightfold, without any increase of percentage
of loss of energy in that conductor, or decrease of
percentage of development of heat in the burner; and thus
enabled the area of the cross-section of that conductor to
be reduced eightfold, and thus to be made with one-eighth of
the amount of copper or other metal, which would be required
if the reduction of diameter of the burner from one-thirty-
second to one-sixty-fourth of an inch had not been made. And
that great reduction in the size and cost of conductors,
involved also a great difference in the composition of the
electric energy employed in the system; that difference
consisting in generating the necessary amount of electrical
energy with comparatively high electromotive force, and
comparatively low current, instead of contrariwise. For this
reason, the use of carbon filaments, one-sixty-fourth of an
inch in diamet