namo. He was possessed of absolute
KNOWLEDGE far beyond that of his contemporaries. This he ad acquired by
the hardest kind of work and incessant experiment with magnets of all
kinds during several years preceding, particularly in connection
with his study of automatic telegraphy. His knowledge of magnets was
tremendous. He had studied and experimented with electromagnets in
enormous variety, and knew their peculiarities in charge and discharge,
lag, self-induction, static effects, condenser effects, and the various
other phenomena connected therewith. He had also made collateral studies
of iron, steel, and copper, insulation, winding, etc. Hence, by reason
of this extensive work and knowledge, Edison was naturally in a position
to realize the utter commercial impossibility of the then best dynamo
machine in existence, which had an efficiency of only about 40 per
cent., and was constructed on the "cut-and-try" principle.

He was also naturally in a position to assume the task he set out to
accomplish, of undertaking to plan and-build an improved type of machine
that should be commercial in having an efficiency of at least 90 per
cent. Truly a prodigious undertaking in those dark days, when from the
standpoint of Edison's large experience the most practical and correct
electrical treatise was contained in the Encyclopaedia Britannica, and
in a German publication which Mr. Upton had brought with him after he
had finished his studies with the illustrious Helmholtz. It was at this
period that Mr. Upton commenced his association with Edison, bringing
to the great work the very latest scientific views and the assistance
of the higher mathematics, to which he had devoted his attention for
several years previously.

As some account of Edison's investigations in this connection has
already been given in Chapter XII of the narrative, we shall not enlarge
upon them here, but quote from An Historical Review, by Charles L.
Clarke, Laboratory Assistant at Menlo Park, 1880-81; Chief Engineer of
the Edison Electric Light Company, 1881-84:

"In June, 1879, was published the account of the Edison dynamo-electric
machine that survived in the art. This machine went into extensive
commercial use, and was notable for its very massive and powerful
field-magnets and armature of extremely low resistance as compared with
the combined external resistance of the supply-mains and lamps. By means
of the large masses of iron in the field-magnets,