110 SCIENCE OF THRESHING. 



the boiler than there is leaving it in the form of 

 steam. The resulting unbalanced pressure thus keeps 

 up the circulation and the injector works contin- 

 uously. 



All joints should be kept tight to prevent air from 

 entering the injector; as air does not condense 

 like steam it would prevent the injector from working 

 properly. 



