e
varies as the square of the speed, should not the power requisite to
overcome that resistance vary as the square of the speed?

_A._--It should if you consider the resistance over a given distance, and
not the resistance during a given time. Supposing the resistance of a
railway train to increase as the square of the speed, it would take four
times the power, so far as atmospheric resistance is concerned, to
accomplish a mile at the rate of 60 miles an hour, that it would take to
accomplish a mile at 30 miles an hour; but in the former case there would
be twice the number of miles accomplished in the same time, so that when
the velocity of the train was doubled, we should require an engine that was
capable of overcoming four times the resistance at twice the speed, or in
other words, that was capable of exerting eight times the power, so far as
regards the element of atmospheric resistance. We know by experience,
however, that it is easier to attain high speeds on railways than in steam
vessels, where the resistance does increase nearly as the square of the
speed.

502. _Q._--Will you describe generally the arrangement of a locomotive
engine?

_A._--The boiler and engine are hung upon a framework set on wheels, and,
together with this frame or carriage, constitute what is commonly called
the locomotive. Behind the locomotive runs another carriage, called the
tender, for holding coke and water. A common mode of connecting the engine
and tender is by means of a rigid bar, with an eye at each end through
which pins are passed. Between the engine and tender, however, buffers
should always be interposed, as their pressure contributes greatly to
prevent oscillation and other irregular motions of the engine.

503. _Q._--How is the framing of a locomotive usually constructed?

_A._--All locomotives are now made with the framing which supports the
machinery situated within the wheels; but for some years a vehement
controversy was maintained respecting the relative merits of outside and
inside framing, which has terminated, however, in the universal adoption of
the inside framing. It is difficult, in engines intended for the narrow
gauge, to get cylinders within the framing of sufficient diameter to meet
the exigencies of railway locomotion; by casting both cylinders in a piece,
however, a considerable amount of room may be made available to increase
their diameters. It is very desirable that the cylinders of locomotives
s