The Sun.
London, England, 1861-10-07 00:00:00

THE SPEED OF STEAMBOATS.

(From the Steam aiming Chronicle.)
In no country, either on this or the other side of the At-
lantic, has so much progress been made in the construction
of steam-boats and their machinery as in England. The
enginemakers of France, Belgium, and Switzerland turn
out some very respectable specimenS of workmanship, but
in many cases this is done by the agency of English work-
men, and almost invariably under English superintendence.
Though the rate of wages is much lower for native than for
English workmen on the continent, yet it is often found
more economic to employ the latter, and it would be very
difficult to go into a foreign factory the superintendent of
which is not a native of these islands. And, notwithstand-
ing the boasts of Brother Jonathan, and his exaggerated
statements as to the performance of his craft he has never yet
produced a steamer which for safety solidity, and speed,
can compete with those turned out of our own workshops.
We look upon the record of the performances of some of
the American river boats as mere "bunkum," and when we
hear of a fabulous number of knots run within the hour, we
regard the statement as we should do one of Colonel Croc-

ket's stories of the number of bears he slaughtered, and as
worthy of as much credit as Barnum's guarantee for his
mermaids. By dint of employing high-pressure engines,
loaded to an absolutely dangerous pressure, and taking cre-
dit for the spepd induced by running down a rapid current,
we believe that high velocities are sometimes obtained on
American tvea-Illit %.ITaiiil RlP.llllAnntAtte,TAVVilial
matt-paexce
„,. 4, Yankees can produce, even though the
.safety-
valve should be loaded to the bursting point. They once
had a fair trial with us in the Atlantic passage, when Col-
lins's boats were built to compete with the Cunard liners,
and they were at last reluctantly compelled to admit their
inferiority.

As far as we have yet progressed in our experience of the
construction of hulls and the application of steam power,
although there is evidently a limitation to the speed that
can be realised in navigation, we have not yet attained
nearly to that limit. At present this limit may be fixed at
something near 30 miles an hour, beyond whieh rate of
speed it would hardly seem possible to propel any vessel.
We are still about 30 per cent. below this standard, nor
does there for all the practical purposes of business appear
any immediate probability of our advancing further. Our
swiftest mail packets do not exceed 1S knots, or a trifle less
than 21 miles an hour through the water, and very few
vessels indeed realise this speed. As a rule, our fast river
packets do not exceed 14 knots, and this seems to be the
standard of general usefulness, as whilst this can be secured
without any sacrifice of economy, all above this rate entails
great expense.

The first and most essential requisite to secure speed in
the construction of a steam-vessel is the form of the hull.
Mere power—although the vessel
,is useless without it in
some form—is quite secondary to the correctness of the
vessel's lines. More steam-vessels are overpowered than un-
derpowered, and it has been frequently found that when
engines of superior horse-power have been taken out of a
vessel, and others of inferior size put into her, her speed has
been most materially increased. And in connection with
steam-boats another fact is evident, that it is not so much a
question of the fineness of the lines fore and aft as it is of the
shape of the vessel amidships, so that full and hollow water-
lines, wave-shape curves, and all the other knick-knackeries
of shipbuilding, are considerations of quitela subordinate
character. It is astonishing what a long time it took to
beat this obvious truth into the heads of our naval archi-
tects. Very many years ago experiments were made with
bluff-headed vessels like barges, in opposition to others
with fine entrances and deliveries, and the difference in
speed was found to be quite unimportant. The result pro-
duced a large amount of surprise, but did not lead to a dis-
covery of the true theory of resistance.
Again, when it was found that by what is termed length-
ening the floor of a vessel, or, in other words, cutting her
in halves and adding to her length amidships, the speed of
the vessel was greatly increased, even when she was of
larger tonnage, and possessed only the same engine-power
as formerly, the discovery again failed to convey a true
perception of the correct theory upon which speed is based.
That theory, it is unneces:ary perhaps to say, is now well
understood, and lies entirely in the size of the midship
section, the immersed area of which forms the only true
point of resistance as the vessel passes through the water.
For this reason large vessels will always haVe the advan-
tage over those of a smaller size, since the width of a small
vessel cannot be reduced consistently with the strength and
stability of the ship. The question as to whether a steamer
is 200 feet or 2,000 yards long is quite unimportant, since
except in encountering currents very little more force would
be necessary to propel the one than the other, provided their
midship sections were uniform in area and displacement.
The great drawback to realising high rates of speed is the
enormous sacrifice of fuel which must be expended where
thie result is to be attained. The resistance in high veloci-
ties increases immensely, and it is very questionable who •
ther in ordinary cases the advantages secured compensate
for the great additional outlay of money. To secure an ad-
ditional mile of speed by mere engine-power, provided all
the other conditions remain the same, is somewhat alarming
in a pecuniary point of view. To keep engines up to their
maximum number of revolutions implies incessant work
at the stoke-holes, and a full consumption of fuel,
whereas the same vessel, with fires partially banked
up, will attain more than two-thirds of her
full speed with a consumption of less than one-half the
amount of coals. A rough gauge of the power of an engne
is furnished by the diameter of her funnel, and the larger the
funnel the greater the draught and the larger the con-
sumption of fuel. There would be no difficulty whatever in
building a steamboat to run at the rate of 25 miles an hour,
but it would cost a little fortune to pay for her weekly sup-
ply of coals. Practically, and for all really economic pur-
poses, 14 or 15 knots an hour is all wo can expect to realise
—all beyond this must be purchased at a cost which is irre-
concilable with the ordinary demands of commerce, and the
pecuniary nature of steamboat speculations.
The most econsmical method of realising high rates of
speed is by the adoption of high-pressure and non-condens-
ing engines. The very words " high-pressure" have a grat-
ing sound upon the ear of steamboat passengers in this
W WII) and are ao§iniMed with the egame,ltlea which occur