keen reasoning powers, his tenacious memory, his fertility of resource;
follows him through a series of innumerable experiments, conducted
methodically, reaching out like rays of search-light into all the
regions of science and nature, and finally exhibits him emerging
triumphantly from countless difficulties bearing with him in new arts
the fruits of victorious struggle.

These volumes aim to be a biography rather than a history of
electricity, but they have had to cover so much general ground in
defining the relations and contributions of Edison to the electrical
arts, that they serve to present a picture of the whole development
effected in the last fifty years, the most fruitful that electricity has
known. The effort has been made to avoid technique and abstruse phrases,
but some degree of explanation has been absolutely necessary in regard
to each group of inventions. The task of the authors has consisted
largely in summarizing fairly the methods and processes employed by
Edison; and some idea of the difficulties encountered by them in
so doing may be realized from the fact that one brief chapter, for
example,--that on ore milling--covers nine years of most intense
application and activity on the part of the inventor. It is something
like exhibiting the geological eras of the earth in an outline lantern
slide, to reduce an elaborate series of strenuous experiments and a vast
variety of ingenious apparatus to the space of a few hundred words.

A great deal of this narrative is given in Mr. Edison's own language,
from oral or written statements made in reply to questions addressed to
him with the object of securing accuracy. A further large part is based
upon the personal contributions of many loyal associates; and it is
desired here to make grateful acknowledgment to such collaborators as
Messrs. Samuel Insull, E. H. Johnson, F. R. Upton, R. N Dyer, S. B.