27 



feet in the ends. Now, half the vertical height, seven 

 feet six inches, multiplied by the length in feet, and 

 added to one and a half time the area of glass in feet, 

 is equal to the cubic feet of air to be warmed in each 

 minute when there are no double doors. 



That is, 7.5 multiplied by 30 added to H, multi- 

 plied by 720=1305 cubic feet. But in a house with 

 wooden bars and rafters, about one tenth of this 

 space will be occupied with woodwork, which is so 

 slow a conductor of heat, that it will not suffer a sen- 

 sible quantity to escape, therefore 130 feet may be 

 deducted, leaving the quantity to be warmed per 

 mimite== 11 75 cubic feet. 



To ascertain the surface of pipe required to warm 

 any given quantity of air, multiply the cubic feet of 

 air to be heated per minute by the difference between 

 the temperature the house is to be kept at, and that 

 of the external air in degrees of Fahrenheit's thermo- 

 meter, and divide the product by 2.1, the difference 

 between 200, which is the temperature of the steam 

 pipes, and the temperature of the house ; the quotient 

 will be the surface of cast-iron pipe required. 



Now, in the house, the dimensions of which are 

 above given, if the lowest temperature in the night be 

 fixed at 50 degs., and 10 degs. are allowed for winds, 

 and the external air is supposed to be at zero or of 

 Fahrenheit, then 1175 multiplied by 60 degs. and 

 the product divided by 2.1, the difference between 



