ENGINE No. 15. 



83 



non-condensing, as was done on the test. Steam is supplied 

 from vertical superheating boilers. A small quantity of steam 

 was drawn from the boilers and used for other purposes than 

 running the engine ; but the quantity is insignificant, and no 

 allowance is made for it. The steam valves and pistons of 

 both cylinders were practically tight. There was a slight 

 amount of leakage in all the exhaust valves. The engine was 

 employed in driving a cotton-mill. 



A test was made on this engine to determine the amount of 

 power used by the air-pump, which had a vertical plunger 22 

 in. diameter and 12-in. stroke. The connecting-rod on the 

 condensing side was disconnected, and cards were taken from 

 the other cylinder first with air-pump in operation and then 

 with air-pump stopped. The load driven in both cases was 

 the shafting of the mill. The difference in the two results 

 was 10.8 horse-power, or 1.8% of the working power of the 

 engine. 



Sample indicator diagrams from the pump cylinder are ap- 

 pended, the first taken under the working conditions, and the 

 second obtained on the power test. 



ENGINE No. 15 AIR PUMP 



Working Conditions 



-30 

 20 



10 



O 



10 



Power Test 



20 



10 







10 



