GENERAL CONDITIONS OF ECONOMY. 



31 



The wasteful effect of a high flue temperature is exhibited by 

 other boilers than those of the horizontal tubular class. This 

 source of waste was shown to be the main cause of the low 

 economy produced in those vertical boilers which are deficient 

 in heating surface. Examples of the same effect are numerous 

 in the case of nearly every type of boiler treated in the paper. 

 The cast-iron sectional boilers Nos. 61 and 63 have flue tem- 

 peratures of 575 degrees and 462 degrees, respectively, and 

 evaporate at the low rate of 9.79 pounds and 9.61 pounds of 

 water from and at 212 degrees per pound of combustible. The 

 five water-tube boilers, referred to below, are likewise wasteful 

 on account of the high temperature of the escaping gases. The 

 temperatures range between 428 degrees and 540 degrees, and 

 the evaporations between 9.68 pounds and 10.36 pounds for 

 anthracite coal, and between 10.79 pounds and 10.98 pounds 

 for bituminous coal, all of which are low results for their re- 

 spective grades of coal. 



The plain cylinder boilers Nos. 47, 48 and 49 have a flue 

 temperature, in the most favorable case, of 567 degrees, and an 

 evaporation of only 9.22 pounds of water from and at 212 de- 

 grees per pound of combustible, and the evaporation is reduced 

 as the flue temperature increases. The Galloway boiler No. 

 50, under extremely favorable circumstances as to kind of fuel, 

 mode of firing and general management, gave an evaporation of 

 only 11.06 pounds, this low result being due, evidently, to the 

 fact that the temperature of the escaping gases was at the high 

 figure of 575 degrees. 



