equip the roads they build; for none others are so well acquainted
with the road as those who from a thorough knowledge of the matter
have established the grades and the curvatures.

The difference between adaptation and non-adaptation will plainly be
seen by the comparison below. The railway from Boston to Albany may
be divided into four sections, of which the several lengths and
corresponding maximum grades are as tabulated.

Length in miles. Steepest grade
Boston to Worcester, 44 30
Worcester to Springfield, 541/2 50
Springfield to Pittsfield, 52 83
Pittsfield to Albany, 431/2 45

A load of five hundred tons upon a grade of thirty feet per mile
requires of the locomotive a drawing-power of 11,500 lbs.

Upon a 50 feet grade 15,500 lbs.
Upon an 83 feet grade 22,500 lbs.
Upon a 45 feet grade 14,500 lbs.

Now, if the engines are all alike, (as they are very nearly,) and
each is able to exert a drawing-power of five thousand pounds to
move a load of five hundred tons from Boston to Albany, we need as
follows:

B. to W.--11500/5000 or 2 engines.
W. to S.--15500/5000 or 3 engines.
S. to P.--22500/5000 or 5 engines.
P. to A.--14500/5000 or 3 engines.

From which the whole number of miles run by engines for one whole
trip would be,--

B. to W. 44 miles by 2 engines, or 88
W. to S. 541/2 miles by 3 engines, or 1631/2
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 fracti