Edison as I know him, by Henry Ford, in collaboration with Samuel Crowther.

EDISON As I KNOW HIM
"Again, could this filamentary conductor be
supported in a vacuum chamber so perfectly
formed and constructed that during all these
hours in which it would be subjected to various
temperatures, not a particle of air could 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 large quantity, and capable of long-distance
shipment without injury. These and a multitude
of minor considerations-minor, but none the
less important-combined to form a problem of
great magnitude.
"As already stated, I found that I could not
use carbon successfully in my earlier experiments,
because the rods or strips of carbon I then employed, although much larger than filaments,
would not stand, but were consumed in a few
minutes under the best conditions I then had at
my command. Now, however, that I had found
means of obtaining and maintaining high vacua,
I immediately went back to carbon, which from
the first I had conceived of as the ideal substance
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