28 SCIENCE OF SUCCESSFUL THRESHING. 



drains the steam space and the other the water space. The 

 steam space may be drained before starting the engine, in 

 order to prevent water from being thrown from the smoke 

 stack. Both water and steam spaces must be drained in 

 cold weather, to prevent freezing. 



Testing and Repairing the Heater. If you suspect that 

 the heater leaks, it may be tested by opening cock farthest 

 from the end, letting all the condensed exhaust escape. 

 Next start the pump, but let the engine stand still. If water 

 issues from this cock, it shows that the heater leaks. Re- 

 pairs are easily made by removing the heads. The tubes 

 may be tightened, or renewed, if necessary, in exactly the 

 same manner as those in the boiler. 



