ing changes and improvements in the mechanism of telegraphy.

His first great success came with the sale of an improvement in the
instruments used to record stock quotations, which enabled these
"tickers" to print the quotations legibly on paper tape, and this
success enabled him to get some capitalists to finance his experiments
with the electric light. The arrangement was that they were to pay the
expense of the experiments and to share in such inventions as resulted.
For the sake of quiet, he moved out to a little place in New Jersey
called Menlo Park, and built himself a shop. Then began that remarkable
series of experiments--one of the most remarkable in history--which
resulted in the perfection of the incandescent lamp.

The problem was to find a material for the filament which would give a
bright light and which, would, at the same time, be durable, and with
this end in view, hundreds and hundreds of different filaments were
tried. The difficulties in the way of this experimenting were enormous,
since the light only burns when in a vacuum, and the instant the vacuum
is impaired, out it goes. At one time, all the lamps he had burning at
Menlo Park, about eighty in all, went out, one after another, without
apparent cause. The lamps had been equipped with filaments of carbon and
had burned for a month. There seemed to be no reason why they should not
burn for a year, and Edison was stunned by the catastrophe. He began at
once the most exhaustive series of experiments ever undertaken by an
American physicist, remaining in his laboratory for five days and
nights, dining at his work bench on bread and cheese, and snatching a
little sleep occasionally, when one of his assistants was on duty. It
was finally discovered that the air had not been sufficiently exhausted
from the lamps.

Again success seemed in sight, but soon the lamps began acting queerly
again. Worn out with fatigue and disappointment, Edison took to his bed.
Ultimate failure was freely predicted, and the price of gas stock rose
again. In five months, the inventor had aged five years, but he was not
yet ready to give up the fight. And at last it was won, and the
incandescent lamp placed on the market. It has not displaced gas, as
some people thought it would, but it is the basis of a business which
made the inventor sufficiently rich to realize his great ambition of
building himself the finest laboratory in the world; where the most
expert iron-workers,