This proved to be a most knotty and intricate puzzle--tricky and
evasive--always leading on and promising something, and at the last
slipping away leaving the work undone. Edison's remarkable patience and
persistence in dealing with this trying problem and in finally solving
it successfully won for him more than ordinary admiration from his
associates. One of them, in speaking of the seemingly interminable
experiments to overcome this trouble, said: "I guess that question of
conductivity of the positive pocket brought lots of gray hairs to his
head. I never dreamed a man could have such patience and perseverance.
Any other man than Edison would have given the whole thing up a thousand
times, but not he! Things looked awfully blue to the whole bunch of
us many a time, but he was always hopeful. I remember one time things
looked so dark to me that I had just about made up my mind to throw up
my job, but some good turn came just then and I didn't. Now I'm glad I
held on, for we've got a great future."

The difficulty of obtaining good electrical contact in the positive
element was indeed Edison's chief trouble for many years. After a great
amount of work and experimentation he decided upon a certain form
of graphite, which seemed to be suitable for the purpose, and then
proceeded to the commercial manufacture of the battery at a special
factory in Glen Ridge, New Jersey, installed for the purpose. There was
no lack of buyers, but, on the contrary, the factory was unable to turn
out batteries enough. The newspapers had previously published articles
showing the unusual capacity and performance of the battery, and public
interest had thus been greatly awakened.

Notwithstanding the establishment of a regular routine of manufacture
and sale, Edison did not cease to experiment for improvement. Although
the graphite apparently did the work desired of it, he was not
altogether satisfied with its performance and made extended trials
of other substances, but at that time found nothing that on the whole
served the purpose better. Continuous tests of the commercial cells were
carried on at the laboratory, as well as more practical and heavy tests
in automobiles, which were constantly kept running around the adjoining
country over all kinds of roads. All these tests were very closely
watched by Edison, who demanded rigorously that the various trials of
the battery should be carried on with all strenuousness so as to get the
utmost re