pages at stations. These
conditions render firing with petroleum very difficult; and were it not
for the part played by properly arranged brickwork inside the fire box,
the spray jet alone would be quite inadequate. Hitherto the efforts of
engineers have been mainly directed toward arriving at the best kind of
"spray injector," for so minutely subdividing a jet of petroleum into a
fine spray, by the aid of steam or compressed air, as to render it
inflammable and of easy ignition. For this object nearly all the known
spray injectors have very long and narrow orifices for petroleum as well
as for steam; the width of the orifices does not exceed from 1/2 mm. to 2
mm. or 0.02 in. to 0.08 in., and in many instances is capable of
adjustment. With such narrow orifices it is clear that any small solid
particles which may find their way into the spray injector along with the
petroleum will foul the nozzle and check the fire. Hence in many of the
steamboats on the Caspian Sea, although a single spray injector suffices
for one furnace, two are used, in order that when one gets fouled the
other may still work; but, of course, the fouled orifices require
incessant cleaning out.

_Locomotives._--In arranging a locomotive for burning petroleum, several
details are required to be added in order to render the application
convenient. In the first place, for getting up steam to begin with, a gas
pipe of 1 inch internal diameter is fixed along the outside of the boiler,
and at about the middle of its length it is fitted with a three-way cock
having a screw nipple and cap. The front end of the longitudinal pipe is
connected to the blower in the chimney, and the back end is attached to
the spray injector. Then by connecting to the nipple a pipe from a
shunting locomotive under steam, the spray jet is immediately started by
the borrowed steam, by which at the same time a draught is also maintained
in the chimney. In a fully equipped engine shed the borrowed steam would
be obtained from a fixed boiler conveniently placed and specially arranged
for the purpose of raising steam. In practice steam can be raised from
cold water to 3 atm. pressure--45 lb. per square inch--in twenty minutes.
The use of auxiliary steam is then dispensed with, and the spray jet is
worked by steam from its own boiler; a pressure of 8 atm.--120 lb.--is
thus obtained in fifty to fifty-five minutes from the time the spray jet
was first started. In daily practice, when it i