we improved
the material, they gradually crept up to over 500. Just about that time
Edison made a trip to Canada, and when he came back we had made such
good progress that the figures had crept up to about 1000. I well
remember how greatly he was pleased."

In speaking of the development of the negative element of the battery,
Mr. Aylsworth said: "In like manner the iron element had to be developed
and improved; and finally the iron, which had generally enjoyed
superiority in capacity over its companion, the nickel element, had to
go in training in order to retain its lead, which was imperative, in
order to produce a uniform and constant voltage curve. In talking
with me one day about the difficulties under which we were working and
contrasting them with the phonograph experimentation, Edison said: 'In
phonographic work we can use our ears and our eyes, aided with powerful
microscopes; but in the battery our difficulties cannot be seen or
heard, but must be observed by our mind's eye!' And by reason of the
employment of such vision in the past, Edison is now able to see quite
clearly through the forest of difficulties after eliminating them one by
one."

The size and shape of the containing pockets in the battery plates or
elements and the degree of their perforation were matters that received
many years of close study and experiment; indeed, there is still to-day
constant work expended on their perfection, although their present
general form was decided upon several years ago. The mechanical
construction of the battery, as a whole, in its present form, compels
instant admiration on account of its beauty and completeness. Mr. Edison
has spared neither thought, ingenuity, labor, nor money in the effort to
make it the most complete and efficient storage cell obtainable, and the
results show that his skill, judgment, and foresight have lost nothing
of the power that laid the foundation of, and built up, other great arts
at each earlier stage of his career.

Among the complex and numerous problems that presented themselves in
the evolution of the battery was the one concerning the internal
conductivity of the positive unit. The nickel hydrate was a poor
electrical conductor, and although a metallic nickel pocket might be
filled with it, there would not be the desired electrical action unless
a conducting substance were mixed with it, and so incorporated and
packed that there would be good electrical contact throughout.