ng his usual custom, Edison would
indicate the lines of experiment to be followed, which were carried
out and recorded in the note-books. He himself, in January, 1879, made
personally a most minute and searching investigation into the properties
and behavior of plating-iridium, boron, rutile, zircon, chromium,
molybdenum, and nickel, under varying degrees of current strength, on
which there may be found in the notes about forty pages of detailed
experiments and deductions in his own handwriting, concluding with the
remark (about nickel): "This is a great discovery for electric light in
the way of economy."

This period of research on nickel, etc., was evidently a trying one, for
after nearly a month's close application he writes, on January 27, 1879:
"Owing to the enormous power of the light my eyes commenced to pain
after seven hours' work, and I had to quit." On the next day appears
the following entry: "Suffered the pains of hell with my eyes last night
from 10 P.M. till 4 A.M., when got to sleep with a big dose of morphine.
Eyes getting better, and do not pain much at 4 P.M.; but I lose to-day."

The "try everything" spirit of Edison's method is well illustrated in
this early period by a series of about sixteen hundred resistance tests
of various ores, minerals, earths, etc., occupying over fifty pages of
one of the note-books relating to the metallic filament for his lamps.

But, as the reader has already learned, the metallic filament was soon
laid aside in favor of carbon, and we find in the laboratory notes an
amazing record of research and experiment conducted in the minute
and searching manner peculiar to Edison's method. His inquiries were
directed along all the various roads leading to the desired goal,
for long before he had completed the invention of a practical lamp he
realized broadly the fundamental requirements of a successful system of
electrical distribution, and had given instructions for the making of
a great variety of calculations which, although far in advance of
the time, were clearly foreseen by him to be vitally important in the
ultimate solution of the complicated problem. Thus we find many hundreds
of pages of the note-books covered with computations and calculations
by Mr. Upton, not only on the numerous ramifications of the projected
system and comparisons with gas, but also on proposed forms of dynamos
and the proposed station in New York. A mere recital by titles of
the vast number of