152 SCIENCE OF THRESHING. 



kerosene or light machine oil on such a pipe, and see 

 how rapidly it evaporates and disappears in smoke 

 and gas. 



The cylinder "lubricators" should furnish a con- 

 tinuous supply of oil to the engine. This supply 

 should be constant although a small quantity will 

 suffice to keep the valve and cylinder rings lubricated. 

 From three to five drops per minute of best grades of 

 cylinder oil will keep the ordinary traction engine well 

 lubricated, while with lighter grades, from five to 

 seven drops should be used. 



Gearing which has to withstand a heavy pressure 

 on the face of its teeth should be lubricated with some 

 kind of hard oil or axle grease. 



In recent years hard oil has come into general use 

 for journal lubrication. 



