Oil Engines. 



453 



is avoided in this engine by governing by holding the exhaust 

 valve open. When the engine exceeds its proper speed the 

 governor interposes a block between the end of the exhaust 

 valve lever and a stop, so that the valve cannot return to its 

 seat. The suction stroke of the piston finds it easier to fill the 

 cylinder with the products of the last working stroke than to 

 open the air valve against the resistance of its spring. No fresh 

 working charge, therefore, enters the cylinder until the fall in 

 speed causes the governor to raise the interposing block. 

 Fig. 16 represents one of the Campbell portable engines. 



Fig. 16.— The Campbell Portable Oil Engine. 



An interesting and economical engine is that made by Messrs. 

 Blackstone & Co. It presents a combination of the automatic 

 ignition and ignition tube systems, and is made in the fixed and 

 portable forms. The vapouriser is of simple form, oil being 

 supplied to it by a small pump, actuated by a vapour valve lever 

 controlled by a governor, which is of disc form and differs from 

 that on any other oil engine. 



Fig. 17 illustrates the special features of this engine. It is 

 an outline view of the cylinder end, with the vapouriser and 

 valve box in section. The engine works on the same cycle as 

 those previously described, In Fig. 16, a is the ignition tube,, 

 which is in the form of an inverted bottle with the neck screwed 

 into a passage which admits combustible mixture into it. The 



