THE PERKINS SYSTEM.

The second marine engine to which I wish to call your attention is one
that has been made with a view to great economy. The principles
followed in its construction are among those suggested by the
President (Sir W.G. Armstrong) in his address. He (you will remember)
pointed out that the direction in which economy in the steam engine
was to be looked for was that of increasing the initial pressure;
although at the same time he said that there were drawbacks in the
shape of greater loss, by radiation, and by the higher temperature at
which the products of combustion will escape. We must admit the fact
of the latter source of loss, when using very high steam, it being
inevitable that temperature of the products of combustion escaping
from a boiler under these conditions must be higher than those which
need be allowed to escape when lower steam is employed; although I
regret to say that in practice in marine boilers working at
comparatively low pressures the products are ordinarily suffered to
pass into the funnel at above the temperature of melted lead. But with
respect to the loss by radiation in the particular engine I am about
to mention--that of Perkins--there is not as much loss as that which
prevails in the ordinary marine boilers, because the Perkins boiler is
completely inclosed, with the result that while there is within the
case a boiler containing steam of 400 lb. on the square inch, and the
fire to generate that steam, the hand may be applied to the casting
itself, which contains the whole of the boiler, without receiving any
unpleasant sensation of warmth. By Mr. Perkins's arrangement, using
steam of 400 lb. in the boiler, it was found, as the result of very
severe trials, conducted by Mr. Rich, of Messrs. Easton and Anderson's