e rises, due to compression, the charge becomes
more and more explosive, until at the completion of this stroke it has
attained the proper proportions of air and oil vapour, and is fired by
the temperature of the vapouriser and that caused by a high compression;
that is, the charge is fired automatically; and once the engine is
running, no heating lamp is required to keep the vapouriser at the
correct temperature. It is necessary, however, to raise it to the
workable temperature at starting. This is known as the Hornsby-Akroyd
method.

Capel's arrangement is also simple and efficient, and has the additional
advantage of being capable of being fitted to their existing gas
engines, the conversion being made in a very short time. This vapouriser
consists primarily of a tubular casting A, on the outside of which are
formed a series of vertical ribs, shown in plan, fig. 46, running to
within a short distance of the flange at one end, as shown in the
section, fig. 45, thus providing an annular space C between the upper
ends of the ribs and the flange. This casting is enclosed by an outer
casing B, which fits well over the inner tube. It has also a number of
small holes drilled near the lower end communicating with the channels
between the ribs. Thus it will be seen that when the gas valve is opened
and suction takes place, air is drawn in through these holes, passes up
into the annular space C below the top flange, from there travels to the
opposite side of vapouriser, and mixes with the oil which is also being
drawn in through a small nipper at N, fig. 45. Both then pass between a
series of pegs, where they become thoroughly mixed, and finally pass on
to the inlet valve V, fig. 47, and so into the cylinder, where the
complete charge is mixed up and compressed and fired in the usual
manner. Iron ignition tubes may be used, and one heating lamp serves a
double purpose in keeping the tube and vapouriser hot at the same time.
This lamp is fed by means of a pump actuated from the side shaft. The
plunger of the pump is loaded with a spiral spring, which may be
adjusted to give any desired pressure, and is kept constant and steady
by means of an air vessel. This pump is shown in fig. 48. It is actuated
by means of a rod and lever from the side shaft of engine. The plunger P
works in a barrel B, which is carried by a small reservoir R, the latter
being in communication with the main oil tank by means of the pipe H.

[Illustration: