PREFACE. WATER-POw Which, a s formerly the chief reliance of
mankind in industry, has been greatly overshadowed in recent times
by the cheapness of coal and the development of the steam-engine.
This condition, while permanent to all immediate practical intents,
is nevertheless, upon a broad view of the subject, merely
temporary. Two hundred and fifty years ago, when unbroken forests
stretched from the Penobscot to the Wabash, the idea of a scarcity
of wood and timber appeared grotesque. At the present day, the idea
of the exhaustion of existing deposits of coal appears equally so.
Nevertheless that time will certainly come. Our depos-its of coal
are finite every ton taken from the miner leaves a t n less to be
mined. Coal does not have the power of reproduction even to the
extent that wood and timber have. It does not, like water, have the
power of rising in the form of vapor after having developed energy
by descending. Coal deposits are simply an enormous store of fuel
in rapid process of destruction by fire. Water, on the other hand,
will continue to stand mankind in good stead long after the
reluctant earth has yielded up its last ton of coal at least, long
after coal has become too inaccessible and consequently too
expensive to be used for power. Recent remarkable developments in
electricity and other . modes of transmitting mechanical energy
have recalled waterpower to something like its former position in
industrial economy. Whereas formerly it was necessary that the
inudustry should be located at the waterfall, it is now possible to
make large use of water-power for industries located many miles
distant. These changed conditions have given a new interest to
water-power anddirected the, attention of investors to sources
which formerly appeared entirely outside the range of practical
consideration. They have also led to some noteworthy improvements
in utilization, development, and transmission of power. These
improvements are embodied in records of engineering societies, in
the pages of engineering journals, in the plans of skillful
engineers, in catalogues and advertisements of machinists. It has
appeared to the writer no unworthy task to review these sources of
information, to select what appears worthy of preservation, or
necessary for the illustration of the subject and put it in an
accessible and preservable form. In other words, to bring the
entire subject of water-power up to date. This is in no sense an
elementary work. It does not deal in axioms, definitions, or the
elements of science. It assumes the reader to be possessed of
elementary notions of mechanics and mathematics. It discusses some
subjects which cannot be made clear without recourse to the higher
mathematics, and in these cases the writer does not hesitate to
plunge boldly into . these branches of analysis. He does not
conceive it necessary to offer any apology for this proceeding. It
is true that there are successful engineers-successful at least in
the sense of obtaining and retaining lucrative employments-who
affect to despise mathematical knowledge, and make a boast of their
ignorance of these branches. As well might the lawyer boast his
ignorance of the common law. Mathematics is the common law of
engineering. It is to engineering what the common law is to the
legal profession...
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