S. to P. 52 miles by 5 engines, or 260
P. to A. 491/2 miles by 3 engines, or 1481/2
______
And the sum, 660

Now suppose, that, by making the engines for the several divisions
strong in proportion to the resistance encountered upon these
divisions, one engine only is employed upon each; our mileage becomes,

B. to W. 44 by 1 or 44
W. to S. 541/2 by 1 or 541/2
S. to P. 52 by 1 or 52
P. to A. 49 by 1 or 491/2
_____
And the sum, 200 miles.

And the saving of miles run is therefore 660 less 200, or 460; and if
500 tons pass over the road daily, the annual saving of mileage
becomes 460 by 313, or 143,980, or 70 per cent. of the whole. The
actual cost for freight-locomotives per ton, per mile run, during
the year ending Sept. 30, 1855, was 384/1000 of a cent; and the above
143,980 miles saved, multiplied by this fraction, amounts to
$55,288 per annum. The actual expense of working the power will not
of course show the whole 70 per cent. of saving, as heavy and strong
engines cost more at first, and cost more to operate, than lighter
ones; but the figures show the effect of correct adaptation. If we
call the saving 50 per cent. only of the mileage, we have then
(as the locomotive power consumes 30/100 of the whole cost of
operating) 50/100 of 30/100, or 15/100, of the whole cost of working
the road, and this by simply knowing how to adapt the machinery to