described by Mr. Jehl: "I was once with Mr. Upton calculating
some tables which he had put me on, when Mr. Edison appeared with a
glass bulb having a pear-shaped appearance in his hand. It was the kind
that we were going to use for our lamp experiments; and Mr. Edison asked
Mr. Upton to please calculate for him its cubic contents in centimetres.
Now Mr. Upton was a very able mathematician, who, after he finished his
studies at Princeton, went to Germany and got his final gloss under that
great master, Helmholtz. Whatever he did and worked on was executed in
a pure mathematical manner, and any wrangler at Oxford would have been
delighted to see him juggle with integral and differential equations,
with a dexterity that was surprising. He drew the shape of the bulb
exactly on paper, and got the equation of its lines with which he was
going to calculate its contents, when Mr. Edison again appeared and
asked him what it was. He showed Edison the work he had already done on
the subject, and told him that he would very soon finish calculating
it. 'Why,' said Edison, 'I would simply take that bulb and fill it
with mercury and weigh it; and from the weight of the mercury and its
specific gravity I'll get it in five minutes, and use less mental energy
than is necessary in such a fatiguing operation.'"

Menlo Park became ultimately the centre of Edison's business life as
it was of his inventing. After the short distasteful period during the
introduction of his lighting system, when he spent a large part of his
time at the offices at 65 Fifth Avenue, New York, or on the actual work
connected with the New York Edison installation, he settled back again
in Menlo Park altogether. Mr. Samuel Insull describes the business
methods which prevailed throughout the earlier Menlo Park days of "storm
and stress," and the curious conditions with which he had to deal as
private secretary: "I never attempted to systematize Edison's business
life. Edison's whole method of work would upset the system of any
office. He was just as likely to be at work in his laboratory at
midnight as midday. He cared not for the hours of the day or the days
of the week. If he was exhausted he might more likely be asleep in the
middle of the day than in the middle of the night, as most of his work
in the way of inventions was done at night. I used to run his office on
as close business methods as my experience admitted; and I would get at
him whenever it suited his c