the duty obtained. It may be worth noticing that, by an accidental
application of these principles to some inward flow turbines, there is
obtained most, if not all, of whatever advantage they are supposed to
possess, but oddly enough this genuine advantage is never mentioned by any
of the writers who are interested in their introduction or sale. The
well-known experiments of Mr. James B. Francis in 1857, and his elaborate
report, gave to hydraulic engineers a vast store of useful data, and since
that period much progress has been made in the construction of turbines,
and literature on the subject has become very complete.

In the limits of a short paper it is impossible to do justice to more than
one aspect of the considerations relating to turbines, and it is now
proposed to bring before the Mechanical Section of the British Association
some conclusions drawn from the behavior of jets of water discharged under
pressure, more particularly in the hope that, as water power is extremely
abundant in Canada, any remarks relating to the subject may not fail to
prove interesting.

Between the action of turbines and that of screw propellers exists an exact
parallelism, although in one case water imparts motion to the buckets of a
turbine, while in the other case blades of a screw give spiral movement to
a column of water driven aft from the vessel it propels forward. Turbines
have been driven sometimes by impact alone, sometimes by reaction above,
though generally by a combination of impact and reaction, and it is by the
last named system that the best results are now known to be obtained.

The ordinary paddles of a steamer impel a mass of water horizontally
backward by impact alone, but screw propellers use reaction somewhat
disguised, and only to a limited extent. The full use and advantages of
reaction for screw propellers were not generally known until after the