These enormous vessels being out of the
question, the designer must reduce the size. But now the City of Paris
will no longer serve as a model, he must look elsewhere for a vessel
of high speed, and smaller scale, and naturally he picks out a torpedo
boat at the other end of the scale. A speed of 24 knots--and it is
claimed even of 25, 26, and 27 knots--has been attained on the mile by
a torpedo boat. But such a performance is useless for our mode of
comparison, as sufficient fuel at this high speed for ten or twelve
hours only at most can be carried--a voyage of, say, 500 miles; while
our steamer is required to carry coal for 3,000 miles. The Russian
torpedo boat Wiborg, for instance, is designed to carry coal for 1,200
miles at 10 knot speed; but at 20 knots this fuel would last only
twenty-seven hours, carrying the vessel 540 miles. It will now be
found that with this limited coal capacity the speed of the ordinary
torpedo boat must be reduced considerably below 10 knots for it to be
able to cross the Atlantic, 3,000 miles under steam. So that, even at
a possible speed of 10 knots for the voyage, the full sized 24 knot
five-day vessel, of which the best torpedo boat is the model, must
have (2.4)^{6}, say 200 times the tonnage, and (2.4)^{7}, or 460 times
the horse power. The enlarged Wiborg would thus not differ much from
the enlarged City of Paris. A better model to select would be one of
the recent dispatch boats, commerce destroyers, or torpedo catchers,
recently designed by Mr. W.H. White, for our navy--the Intrepid or
Endymion, for instance. The Intrepid is 300 ft. by 44 ft., 3,600 tons,
and 9,000 horse power for 20 knot speed, with 800 hours' coal capacity
for 8,000 miles at 10 knot speed; which will reduce to 3,000 miles at
16 knots, and 2,000 miles at 20 knots.

The Endymion is 360 ft. by 60 ft., with coal capacity for 2,800 miles
at 18 knot speed, or for about 144 hours or six days. The enlarged
Endymion for the same voyage of 2,800 miles in five days, or at 211/2
knot speed, would be 44 per cent larger and broader, that is 520 ft.
by 86 ft., and of threefold tonnage, and three and a half times, or
about 30,000 horse power--about the dimensions of the Furst Bismarck,
but much more powerfully engined. This agrees fairly with the estimate
in the SCIENTIFIC AMERICAN of 19th Sept, 1891., where it is stated
that twenty-two boilers, at a working pressure of 180 lb. on the
square inch, would be required, allowing 1