thout some mention of the general outline of his work, and reference
may be made briefly to a few of the chief items. And lest the reader
think that the word "innumerable" may have been carelessly or hastily
used above, we would quote the reply of one of the laboratory assistants
when asked how many experiments had been made on the Edison storage
battery since the year 1900: "Goodness only knows! We used to number our
experiments consecutively from 1 to 10,000, and when we got up to
10,000 we turned back to 1 and ran up to 10,000 again, and so on. We ran
through several series--I don't know how many, and have lost track of
them now, but it was not far from fifty thousand."

From the very first, Edison's broad idea of his storage battery was to
make perforated metallic containers having the active materials packed
therein; nickel hydrate for the positive and iron oxide for the negative
plate. This plan has been adhered to throughout, and has found its
consummation in the present form of the completed commercial cell, but
in the middle ground which stands between the early crude beginnings
and the perfected type of to-day there lies a world of original thought,
patient plodding, and achievement.

The first necessity was naturally to obtain the best and purest
compounds for active materials. Edison found that comparatively little
was known by manufacturing chemists about nickel and iron oxides of the
high grade and purity he required. Hence it became necessary for him to
establish his own chemical works and put them in charge of men specially
trained by himself, with whom he worked. This was the plant at Silver
Lake, above referred to. Here, for several years, there was ceaseless
activity in the preparation of these chemical compounds by every
imaginable process and subsequent testing. Edison's chief chemist says:
"We left no stone unturned to find a way of making those chemicals so
that they would give the highest results. We carried on the experiments
with the two chemicals together. Sometimes the nickel would be ahead
in the tests, and then again it would fall behind. To stimulate us to
greater improvement, Edison hung up a card which showed the results
of tests in milliampere-hours given by the experimental elements as we
tried them with the various grades of nickel and iron we had made. This
stirred up a great deal of ambition among the boys to push the figures
up. Some of our earliest tests showed around 300, but as