Oil-Engines in Relation to Agriculture. 
151 
but a compound of various bodies which boil at temperatures differ- 
ing from each other by many degrees. When, therefore, petroleum 
is evaporated (as in the case of method No. 3) by moderate heat, first, 
its more, and, afterwards, its less volatile constituents are successively 
vaporised, until there remains a very considerable residue which is 
so difficult to evaporate as to be practically useless. 
When, on the other hand, mineral oil is gasified by great heat (as 
in method No. 4), a quantity of tarry matters are produced which, 
passing into the motor with the gas, become deposited in the 
cylinder and its passages to such an extent as seriously to interfere 
with the working of the engine. 
Some one or other of the difficulties here enumerated pre- 
vented the success of the oil-engine until Eteve conceived the idea 
of first spraying, and then evaporating, the complex compound called 
An Oil-engine. 
A, oil tank. E, fly-wheel. L, governor. 
B, lever of hand pump for P, top valve of cylinder. 0, vaporizer. 
starting. G, battery. V, air-pump. 
C, cock lever. K, tappet lever attached to 
D, cylinder. lower valve of cylinder. 
petroleum, a plan which has been successfully reduced to practice in 
this country by Messrs. Priestman Brothers, of Hull. Only the 
“ safe ” oil, which, being everywhere used for lighting, is everywhere 
procurable, is employed. This, flowing from a suitable tank, is first 
converted into the finest possible spray by its passage, under pres- 
sure, through a suitable nozzle, or spray-maker. In this finely 
divided condition, it enters a heated chamber, where the oil-spray is 
vaporised, and whence it passes to the motor, becoming mixed, on 
its way, with a proper quantity of air, the compound being finally 
exploded in the cylinder, as in a gas-engine. The products of com- 
bustion leave the cylinder at a very high temperature, and the ex- 
haust is utilised to maintain the required heat in the vaporising 
chamber. 
Under this system, it is of no consequence whether the whole of 
the oil-spray becomes vaporised before explosion, or not j for its 
