n
praise of one description of turbine above another. But generally, it is of
no consequence whatever how a stream of water may be led through the
buckets of any form of turbine, so long as its velocity gradually becomes
reduced to the smallest amount that will carry it freely clear of the
machine.

The character of theoretical information imparted by some _Chicago Journal
of Commerce_, dated 20th February, 1884. There we are informed that "the
height of the fall is one of the most important considerations, as the same
stream of water will furnish five times the horse power at ten ft. that it
will at five ft. fall." By general consent twice two are four, but it has
been reserved for this imaginative writer to make the useful discovery that
sometimes twice two are ten. Not until after the translation of Captain
Morris' work on turbines by Mr. E. Morris in 1844, was attention in America
directed to the advantages which these motors possessed over the gravity
wheels then in use. A duty of 75 per cent. was then obtained, and a further
study of the subject by a most acute and practical engineer, Mr. Boyden,
led to various improvements upon Mr. Fauneyron's model, by which his
experiments indicated the high duty of 88 per cent. The most conspicuous
addition made by Mr. Boyden was the diffuser. The ingenious contrivance had
the effect of transforming part of whatever velocity remained in the stream
after passing out of a turbine into an atmospheric pressure, by which the
corresponding lost head became effective, and added about 3 per cent. to
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