meet very heavy demands made upon it for a short time. I think I am
right in saying that, at the ordinary pressure which Sir William
Armstrong uses in practice, viz., 700 lb. to the square inch, one foot
a second of motion along an inch pipe would deliver at the rate to
produce one-horse power. Therefore, a ten-inch pipe, with the water
traveling at no greater pace than three feet in a second, would
deliver 300 horse-power. This 300 horse-power would no doubt be
somewhat reduced by the loss in the hydraulic engine, which would
utilize the water. But the total energy received would be equivalent
to producing 300 horse-power. Such a transmission would be effected
with an exceedingly small loss infliction in transit. I believe I am
right in saying that a 10 inch pipe a mile long would not involve much
more than about 14 or 15 lb. differential pressure to propel the
water through it at the rate of three feet in a second. If that be so,
then, with 700 lb. to the inch, the loss under such circumstances
would be only two per cent. in transmission. There is no doubt that
this transmission of power hydraulically has been of the greatest
possible use. It has enabled work to be done which could not be done
before. Enormous weights are raised with facility wherever required,
as by the aid of power hydraulically transmitted, it is perfectly easy
for one man to manage the heaviest cranes. Moreover, as I have said in
other places, the system which we owe to Sir William Armstrong has
gone far to elevate the human race, and it has done so in this manner.
So long as it is competent for a man to earn a living by mere
unintelligent exercise of his muscles, he is very likely to do it. You
may see in the old London docks the crane-heads covered by structures
that look like paddle-boxes. If you go to them, there is, I am glad to
say, nothing now to fill them up; but when the British Association
first met, these paddle-boxes covered large tread-wheels, in which men
trod, so as to raise a weight. Now, although I know that in fact there
is nothing more objectionable in a man turning a wheel by treading
inside of it than there is if he turn it round by a winch-handle, yet
somehow it strikes one more as being merely the work of an animal, a
turnspit, or a squirrel, or, indeed, as the task imposed on the
criminal. But, nevertheless, in this way there were a large number of
persons getting their living by the mere exercise of their muscles,
but, as