son's invention incandescent lamps had been suggested as
a possibility, but they were provided with carbon rods or strips of
relatively low resistance, and to bring these to incandescence required
a current of low pressure, because a current of high voltage would pass
through them so readily as not to generate heat; and to carry a current
of low pressure through wires without loss would require wires of
enormous size. [8] Having a current of relatively high pressure to
contend with, it was necessary to provide a carbon burner which, as
compared with what had previously been suggested, should have a very
great resistance. Carbon as a material, determined after patient search,
apparently offered the greatest hope, but even with this substance the
necessary high resistance could be obtained only by making the burner
of extremely small cross-section, thereby also reducing its radiating
surface. Therefore, the crucial point was the production of a hair-like
carbon filament, with a relatively great resistance and small radiating
surface, capable of withstanding mechanical shock, and susceptible of
being maintained at a temperature of over two thousand degrees for a
thousand hours or more before breaking. And this filamentary conductor
required to be supported in a vacuum chamber so perfectly formed and
constructed that during all those hours, and subjected as it is to
varying temperatures, not a particle of air should enter to disintegrate
the filament. And not only so, but the lamp after its design must not
be a mere laboratory possibility, but a practical commercial article
capable of being manufactured at low cost and in large quantities. A
statement of what had to be done in those days of actual as well as
scientific electrical darkness is quite sufficient to explain Tyndall's
attitude of mind in preferring that the problem should be in Edison's
hands rather than in his own. To say that the solution of the problem
lay merely in reducing the size of the carbon burner to a mere hair, is
to state a half-truth only; but who, we ask, would have had the temerity
even to suggest that such an attenuated body could be maintained at a
white heat, without disintegration, for a thousand hours? The solution
consisted not only in that, but in the enormous mass of patiently
worked-out details--the manufacture of the filaments, their uniform
carbonization, making the globes, producing a perfect vacuum, and
countless other factors, the omis