The steam engine familiarly explained and illustrated; with an historical sketch of its invention and progressive improvement; its applications to navigation and railways; with plain maxims for railway speculators. By the Rev. Dionysius Lardner ... With additions and notes by James Renwick ...

STEAM NAVIGATION. 265
and measured 500 tons; the COLUMBIA had 120 horses, and
measured 360 tons.
In general, it may be assumed that for the shortest class
of trips, such as those of the Margate steamers, and the
packets between Liverpool or Holyhead and Dublin, the
proportion of the power to the tonnage should be that of 1
horse-power to every 2 tons by measure; while for the
longest voyages the proportion would be reduced to 1 horse
to 4 tons, voyages of intermediate lengths having every
variety of intermediate proportion.
Steamers thus proportioned in their power and tonnage
may then, on an average of weathers, be expected to make
7, miles an hour while steaming, which is equivalent to 174
miles per day of twenty-four hours. But, in very long
voyages, it rarely happens that a steamer can worlk constantly without interruption. Besides stress of weather, in
which she must sometimes lie-to, she is liable to occasional
derangements of her machinery, and more especially of her
paddles. In almost every long voyage hitherto attempted,
some time has been lost in occasional repairs of this nature
while at sea. We shall perhaps, therefore, for long voyages,
arrive at a more correct estimate of the daily run of a steamer
by taking it at 160 miles.*
By a series of carefully conducted experiments on the
consumption of coals, under marine boilers and common
land boilers, which have been lately made at the works of
Mr. Watt, near Birmingham, it has been proved that the
* The American reader will hardly be able to refrain from a smile at this
estimate of Dr. Lardner of the speed of steamboats, founded upon the most
improved practice of Europe at the close of the year 1835. The boats on the
Hudson river have for years past averaged a speed of 15 miles per hour, and
the Lexington, which was constructed for a navigation part of which is performed in the open ocean, could probably keep up a speed of the same amount,
except in severe storms. With boats, constructed on the principles of those
which navigate Long Island Sound and the Chesapeake, we should not fear to
assume 12 miles per hour, or upward of 280 miles per day, as their average
rate of crossing the ocean.-x. i.
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