gauge locomotive, of average power,
varies from L1,900 to L2,200; it will run on an average 130 miles per day,
at a cost for repairs of 2-1/2d. per mile; and the cost of locomotive
power, including repairs, wages, oil, and coke, does not much exceed 6d.
per mile run, on economically managed railways. This does not include a
sinking fund for the renewal of the engines when worn out, which may be
taken as equivalent to 10 per cent. on their original cost.

497. _Q._--Does the expense of traction increase much with an increased
speed?

_A._--Yes; it increases very rapidly, partly from the undulation of the
earth when a heavy train passes over it at a high velocity, but chiefly
from the resistance of the atmosphere and blast pipe, which constitute the
greatest of the impediments to motion at high speeds. At a speed of 30
miles an hour, the atmospheric resistance has been found in some cases to
amount to about 12 lbs. a ton; and in side winds the resistance even
exceeds this amount, partly in consequence of the additional friction
caused from the flanges of the wheels being forced against the rails, and
partly because the wind catches to a certain extent the front of every
carriage, whereby the efficient breadth of each carriage, in giving motion
to the air in the direction of the train, is very much increased. At a
speed of 30 miles an hour, an engine evaporating 200 cubic feet of water in
the hour, and therefore exerting about 200 horses power, will draw a load
of 110 tons. Taking the friction of the train at 7-1/2 lbs. per ton, or 825
lbs. operating at the circumference of the driving wheel--which, with 5 ft.
6 in. wheels, and 18 in. stroke, is equivalent to 4,757 lbs. upon the
piston--and taking the resistance of the blast pipe at 6 lbs. per square
inch of the pistons, and the friction of the engine unloaded at 1 lb. per
square inch, which, with pistons 12 in. in diameter, amount together to
1,582 lbs., and reckoning the increased friction of the engine due to the
load at 1/7th of the load, as in some cases it has been found
experimentally to be, though a much less proportion than this would
probably be a nearer average, we have 7018.4 lbs. for the total load upon
the pistons. At 30 miles an hour the speed of the pistons will be 457.8
feet per minute, and 7018.4 lbs. multiplied by 457.8 ft. per minute, are
equal to 3213023.5 lbs. raised one foot high in the minute, which, divided
by 33,000, gives 97.3 horses power as the