72 ROUGH-AND-TUMBLE ENGINEERING 



caused by the heat from the burning straw will produce 

 the pressure desired. You should know, however, that 

 your safety is in perfect order. When the water begins 

 to escape at the safety valve, you can readily see if you 

 have expanded your flues sufficiently to keep them from 

 leaking. 



This makes a very nice and steady pressure, and al- 

 though the pressure is caused by heat, it is a cold water 

 pressure, as the water is not heated beyond one or two 

 degrees. This mode of testing, however, cannot be ap- 

 plied in very cold weather, as water has no expansive 

 force within a range of five degrees around the freez- 

 ing point. 



These tests, however, are only for the purpose of try- 

 ing your flues and are not intended to ascertain the ef- 

 ficiency or strength of your boiler. When this is required, 

 I would advise you to get an expert to do it, as the best 

 test for this is the hammer test, and only an expert should 

 attempt it. 



