pers" and the rise
and fall of countless fortunes. And although one cannot estimate in
definite figures the extent of Edison's influence in the enormous
increase of copper production, it is to be remembered that his basic
inventions constitute a most important factor in the demand for the
metal. Besides, one must also give him the credit, as already noted,
for having recognized the necessity for a pure quality of copper for
electric conductors, and for his persistence in having compelled the
manufacturers of that period to introduce new and additional methods
of refinement so as to bring about that result, which is now a sine qua
non.

Still considering his influence on other staples and collateral trades,
let us enumerate briefly and in a general manner some of the more
important and additional ones that have been not merely stimulated, but
in many cases the business and sales have been directly increased and
new arts established through the inventions of this one man--namely,
iron, steel, brass, zinc, nickel, platinum ($5 per ounce in 1878, now
$26 an ounce), rubber, oils, wax, bitumen, various chemical compounds,
belting, boilers, injectors, structural steel, iron tubing, glass,
silk, cotton, porcelain, fine woods, slate, marble, electrical measuring
instruments, miscellaneous machinery, coal, wire, paper, building
materials, sapphires, and many others.

The question before us is, To what extent has Edison added to the wealth
of the world by his inventions and his energy and perseverance? It will
be noted from the foregoing that no categorical answer can be offered
to such a question, but sufficient material can be gathered from a
statistical review of the commercial arts directly influenced to afford
an approximate idea of the increase in national wealth that has been
affected by or has come into being through the practical application of
his ideas.

First of all, as to inventions capable of fairly definite estimate, let
us mention the incandescent electric light and systems of distribution
of electric light, heat, and power, which may justly be considered as
the crowning inventions of Edison's life. Until October 21, 1879, there
was nothing in existence resembling our modern incandescent lamp.
On that date, as we have seen in a previous chapter, Edison's labors
culminated in his invention of a practical incandescent electric lamp
embodying absolutely all the essentials of the lamp of to-day, thus
opening to the