ue to the rapid generation of steam is termed
"false water." To economize fuel, the variable expansion gear, if the
engine has one, should be adjusted to the load, and the blast pipe should
be worked with the least possible contraction; and at stations the damper
should be closed to prevent the dissipation of heat.

747. _Q._--In starting from a station, what precautions should be observed
with respect to the feed?

_A._--In starting from a station, and also in ascending inclined planes,
the feed water is generally shut off; and therefore before stopping or
ascending inclined planes, the boiler should be well filled up with water.
In descending inclined planes an extra supply of water may be introduced
into the boiler, and the fire may be fed, as there, is at such times a
superfluity of steam. In descending inclined planes the regulator must be
partially closed, and it should be entirely closed if the plane be very
steep. The same precaution should be observed in the case of curves, or
rough places on the line, and in passing over points or crossings.

748. _Q._--In approaching a station, how should the supply of water and
fuel be regulated?

_A._--The boiler should be well filled with water on approaching a station,
as there is then steam to spare, and additional water cannot be
conveniently supplied when the engine is stationary. The furnace should be
fed with small quantities of fuel at a time, and the feed should be turned
off just before a fresh supply of fuel is introduced. The regulator may, at
the same time, be partially closed; and if the blast pipe be a variable
one, it will be expedient to open it widely while the fuel is being
introduced, to check the rush of air in through the furnace door, and then
to contract it very much so soon as the furnace door is closed, in order to
recover the fire quickly. The proper thickness of coke upon the grate
depends upon the intensity of the draught; but in heavily loaded engines it
is usually kept up to the bottom of the fire door. Care, however, must be
taken that the coke does not reach up to the bottom row of tubes so as to
choke them up. The fuel is usually disposed on the grate like a vault; and
if the fire box be a square one, it is heaped high in the corners, the
better to maintain the combustion.

749. _Q._--How can you tell whether the feed pumps are operating properly?

_A._--To ascertain whether the pumps are acting well, the pet cock must be
turned, and i