BOILEE No. 71. 233 



position, the draught in the main flue remaining the same, the 

 amount realized was 0.09 of an inch before stopping up the 

 openings, and 0.20 of an inch after stopping them up. The 

 crevices were not fully closed, else the full draught would 

 have been realized when the damper was partially open. 

 Repeated tests, made beforehand, with open crevices, showed 

 a lower economic result than that given here, and this proves 

 that the leakage of too much air into a furnace produces an 

 unfavorable effect upon the economy. 



