Trans. N. Y. Ac. Set. TO Dec. 19, 



in which ^ represents the quantity of heat in units of heat per second, 

 and c the specific heat of air at constant pressure {c = 0.238.) 



All of the above formulas are well known. The following are 

 believed to be new : 



The quantity of heat imparted to the air may also be represented 



by <p'= ^' '^«~-^'') in which is the quantity of heat imparted per 

 3600 



second, and as from the nature of the problem f = <p' we have 



~^oo^"^ = '""■ '• ^^« - ^"^ (^°^ 



or T - T = ^LliiT-J^_ . . (II) 



W.c. 3600 ^ ' 



combining this equation with (8) we have — 



3600 2g H. 



and S' = %^- '^■'- ^^, . . . (13) 



3600 



This expression gives the total heating surface in the pipes in terms 

 of the velocity, the height of the flue, the weight of air discharged per 

 second, and the absolute temperature of the external air. 



If we substitute for V its value in terms of V, the actual velocity, 



we have — 



_ K'^ V^ W. c. T, , s 



^ - Vsht^t;- tj • • ^'^^ 



3600 

 and others fV. = B, V. A. 



3600 



another expression for S'. 



These two expressions exhibit the laws of the movement of the air, 

 giving the quantity of heating surface required under any special con- 

 ditions of area and height of flue, temperature of external air, and 

 velocity of discharge. 



The constant (r) may be found approximately from the experiments 

 of Mr. C. B, Richards, made at Colts Arms Co., of Hartford. The 

 constant A" depends upon the frictional resistance which the air 

 encounters in its passage into and through the flues. The velocity V 

 may be assumed, and should not be greater than four or five feet per 

 second. The smaller the velocity and the larger the flues, the less will 

 be tne required heating surface, and the greater the economy of the 

 apparatus for ventilation. 



