The water powers I have named are but a small fraction of the whole
amount existing in the United States and the adjoining Dominion of
Canada. There is Niagara, with its two or three millions of horse power;
the St. Lawrence, with its succession of falls from Lake Ontario to
Montreal; the Falls of St. Antony, at Minneapolis; and many other falls,
with large volumes of water, on the upper Mississippi and its branches.
It would be a long story to name even the large water powers, and the
smaller ones are almost innumerable. In the State of Maine a survey of
the water power has recently been made, the result, as stated in the
official report, being "between one and two millions of horse power,"
part of which will probably not be available. There is an elevated
region in the northern part of the South Atlantic States, exceeding in
area one hundred thousand square miles, in which there is a vast amount
of water power, and being near the cotton fields, with a fine climate,
free from malaria, its only needs are railways, capital, and population,
to become a great manufacturing section.

The design and construction of the works for developing a large water
power, together with the necessary arrangements for utilizing it and
providing for its subdivision among the parties entitled to it according
to their respective rights, affords an extensive field for civil
engineers; and in view of the vast amount of it yet undeveloped, but
which, with the increase of population and the constantly increasing
demand for mechanical power as a substitute for hand labor, must come
into use, the field must continue to enlarge for a long time to come.

There are many cases in which the power of a waterfall can be made
available by means of compressed air more conveniently than by the
ordinary motors. The fall may be too small to be utilized by the
ordinary motors; the site where the power is wanted may be too distant