sults and develop any possible weakness. So insistent was he on
this, that if any automobile should run several days without bursting a
tire or breaking some part of the machine, he would accuse the chauffeur
of picking out easy roads.

After these tests had been going on for some time, and some thousands
of cells had been sold and were giving satisfactory results to the
purchasers, the test sheets and experience gathered from various sources
pointed to the fact that occasionally a cell here and there would show
up as being short in capacity. Inasmuch as the factory processes were
very exact and carefully guarded, and every cell was made as uniform as
human skill and care could provide, there thus arose a serious problem.
Edison concentrated his powers on the investigation of this trouble, and
found that the chief cause lay in the graphite. Some other minor matters
also attracted his attention. What to do, was the important question
that confronted him. To shut down the factory meant great loss and
apparent failure. He realized this fully, but he also knew that to go
on would simply be to increase the number of defective batteries in
circulation, which would ultimately result in a permanent closure
and real failure. Hence he took the course which one would expect of
Edison's common sense and directness of action. He was not satisfied
that the battery was a complete success, so he shut down and went to
experimenting once more.

"And then," says one of the laboratory men, "we started on another
series of record-breaking experiments that lasted over five years.
I might almost say heart-breaking, too, for of all the elusive,
disappointing things one ever hunted for that was the worst. But secrets
have to be long-winded and roost high if they want to get away when the
'Old Man' goes hunting for them. He doesn't get mad when he misses them,
but just keeps on smiling and firing, and usually brings them into camp.
That's what he did on the battery, for after a whole lot of work he
perfected the nickel-flake idea and process, besides making the great
improvement of using tubes instead of flat pockets for the positive. He
also added a minor improvement here and there, and now we have a finer
battery than we ever expected."

In the interim, while the experimentation of these last five years was
in progress, many customers who had purchased batteries of the original
type came knocking at the door with orders in their hands for ad