the latter only stipulating that it was to be of the same power as the
engine already contracted for. As I was quite convinced that economy was
due to the system rather than to the higher pressure, it was decided not
to increase the boiler pressure more than was necessary to suit the
triple system. The other three ships already alluded to were being fitted
with engines having cylinders 25 inches and 50 inches diameter by 45
inches stroke, and supplied with steam of 90 lb. pressure from a double
ended boiler 13 feet 9 inches diameter by 15 feet long, having a total
heating surface of 2,310 feet, so that these engines have every
qualification for being economical so far as general proportions go, the
stroke being an abnormally long one and the boiler of ample size.
Experience has since shown that these engines are economical in coal,
and the wear and tear exceptionally small.

The new engines for the fourth boat were made with considerably shorter
stroke, and the cylinders proportioned so as to give equal power; they
are 21 inches, 32 inches, and 56 inches diameter by 36 inches stroke, the
high pressure cylinder being supported on columns immediately over the
medium cylinder, and in other respects these engines were made as near as
possible like the other ones above named. Steam at 110 lb. pressure is
supplied from a double ended boiler 12 feet 9 inches diameter and fifteen
feet long, having a total heating surface of 2,270 square feet, and
identical in design with the boiler supplied for the other engines. The
propellers were made exactly alike in all respects, and the ships being
likewise precisely alike, a comparison of the performances of the one
fitted with the triple engines could be made with as little grounds for
differences of opinion as is possible. One of the ships fitted with the
ordinary compound engines was named the Kovno, that with the triple
compound engines the Draco. Their dimensions are as follows: