publication of papers by the present writer in the "Proceedings" of the
Institution of Naval Architects for 1867 and 1868, and more fully in the
"Transactions" of the Society of Engineers for 1868. Since that time, by
the author of these investigations then described, by the English
Admiralty, and by private firms, further experiments have been carried out,
some on a considerable scale, and all corroborative of the results
published in 1868. But nothing further has been done in utilizing these
discoveries until the recent exigencies of modern naval warfare have led
foreign nations to place a high value upon speed. Some makers of torpedo
boats have thus been induced to slacken the trammels of an older theory and
to apply a somewhat incomplete form of the author's reaction propeller for
gaining some portion of the notable performance of these hornets of the
deep. Just as in turbines a combination of impact and reaction produces the
maximum practical result, so in screw propellers does a corresponding gain
accompany the same construction.

[Illustration: FIG. 1.]

[Illustration: FIG. 2.]

_Turbines_.--While studying those effects produced by jets of water
impinging upon plain or concave surfaces corresponding to buckets of
turbines, it simplifies matters to separate these results due to impact
from others due to reaction. And it will be well at the outset to draw a
distinction between the nature of these two pressures, and to remind
ourselves of the laws which lie at the root and govern the whole question
under present consideration. Water obeys the laws of gravity, exactly like
every other body; and the velocity with which any quantity may be falling
is an expression of the full amount of work it contains. By a sufficiently
accurate practical rule this velocity is eight times the square root of the