AMERICAN 
JOURNAL OF SCIENCE AND ARTS. 
[THIRD SERIES] 
Art. XIIL—On the Eva orative Efficiency of Steam Boilers; by 
Wm. P. Tuowsnings, Professor of Dynamic Engineering 
i the Sheffield Scientific School. 
Transfer of heat.—The quantity of water which a steam 
iler apparatus will evaporate In a given time sp gc 
Prmarily upon the temperatures to which those parts 0 - 
Gon Surface in a unit of time, and also on the kind of com- 
; : : . . bined 
“signating that in which no combustible gases or uncom 
oxygen fh to the chimney. This condition is pres adie 
0 give rise to the highest possible temperatures in the resi 
of fuel, and in the escaping products. h i 
© quantity of fuel burned, the constitution of the fellowine 
and the resulting temperatures, depend on the following 
Conditions ; »ina 
: 7 The quantity of air which passes through the furnace in 
nit of time, ‘ . ae 
The amount of surface of the fuel with which this air 
Comes in conta ithin + 
The quantity of heat transferred to the water Aibogase 4c 
boiler will then depend on the amount of heating su 
Am. Jour. So1,—Turap Series, VoL. IV, No. 20.—Avaust, 1872. 
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