The Trials of Oil Engines at Cambridge. 713 
hands of a farm-labourer. But where a mechanic is available 
no difficulty is likely to be encountered on this account. 
Messrs. Clarke, Chapman & Co., Ltd., Gateshead-on-Tyne. — 
Messrs. Clarke, Chapman & Co.’s engine (6 horse-power, 150Z.) 
was the only competing engine in which electric ignition is used. 
The arrangements are illustrated in fig. 13, p. 714. 
The air supply is, as in the last case, by an automatic inlet 
valve opened by the suction of the piston. A charge of petro- 
leum mixed with a small volume of air enters at the back of this 
valve under a constant head, and passes on into the vaporiser 
through a throttle valve controlled by the governor. The vaporiser 
is heated by the exhaust, and discharges its contents through a 
rotating 4-chamber valve which acts both as vapour and exhaust 
valve. This is driven at a quarter of the speed of the engine 
by a lay shaft. The governor is of the flywheel type, and opens 
or closes the throttle valve so as to admit a larger or smaller 
charge of unvarying richness. The charge is exploded at the 
end of the compression stroke by an electric spark, from an in- 
duction coil excited by a bichromate battery. The battery is 
charged about every second day with lb. of acid mixture in 
the form of a damp red paste. This costs 4 d. a pound. 
At starting, a small quantity of benzoline is used, which 
explodes at atmospheric temperature, and so starts the engine 
without the aid of an external lamp, and with exceptional quick- 
ness and ease. 
The single valve can be removed and cleaned in a very few 
minutes, and the simplicity and compactness of the engine are 
remarkable. The use of benzoline and the electric ignition are 
objectionable for farm purposes, where the storage of supplies 
for a long period is often necessary, and would in this case be 
attended with a certain amount of risk. 
The quantity of benzoline required is, however," so exceed- 
ingly small, and the ease with which it starts the engine so great, 
that its use is a distinct advantage under other circumstances. 
The engine only ran for two days satisfactoi’ily. On the 
third day, after a considerable amount of trouble had been ex- 
perienced and the engine had stopped a number of times, it was 
finally withdrawn. On opening up, a leak was found in the 
vaporiser casting, which was sufficient to account for the 
stoppage. 
There seems no reason to doubt that this engine can be 
made a successful and fairly economical one. Its consumption 
for the period for which it ran was high, and there were distinct 
signs of unburnt oil vapour issuing from the exhaust pipe. The 
speed was about 200 per minute, but varied a good deal. In 
