It is necessary here to observe, that the calculation taken for the
consumption of coals is founded upon the basis that the coals are of
the very best quality, and also that the machinery is of the best and
most economical description and construction, and for a vessel of
240-horse power. The time that the steamers are considered to be
engaged in actual work is calculated to include the time passed in
getting up the steam in each voyage, and also to cover all temporary
stoppages. The time allowed on every route and station is, on the
average, more than will be required. Steamers of the force mentioned
will, in good weather and light breezes and seas, even when contrary,
run ten geographical miles per hour; and, within the tropics, with
trade-winds and currents in their favour, at a still greater
speed: but the average performance may be fairly taken at 200 (p. 035)
geographical miles each twenty-four hours, although in all the
climates within the variable winds, and in the tropics when going
against the winds and currents, the speed made good will be, and is
taken at, much less. Moreover it is proper to observe, on the point of
outlay for coals, that the work is everywhere, as regards the quantity
to be used, calculated as if wholly done by steam, while it is obvious
that the assistance of sails may be had recourse to with advantage.
For this purpose, those steamers which have to go into the torrid zone
ought to be provided with large square fore-sails. The assistance to
be obtained by the use of sails would save a considerable quantity of
coals; or what is the same thing, using them would expedite the
steamer proportionally more on her voyage, and bring it so much sooner
to a close. Sails may fairly be calculated to impel a vessel at the
rate of 2-1/2 miles per hour on a voyage, and which will save either
directly _one-fourth_ the quantity of coals, or impel the steamer so
much sooner to the end of her journey than the time calculated, where
time is taken as if it were impelled by steam alone, and thereby a
proportional saving of fuel will be effected. The saving effected on
this ratio will, on the General Plan, be 27,000 tons, 33,250_l._; on
the West Indian portion thereof 7500 tons, 9375_l._; and on the West
Indian and the Falmouth and Fayal department, 9600 tons, 11,475_l._;
subject to 10 per cent. deduction, being allowance for wastage.

As regards the calculations made concerning the progress of steamers
in