Houses and other Buildings. 237 



volutions of the first motion take place, while the current 

 causing those revohitions moves through forty-six feet. 



In order to ascertain the power and merits of a stove, I ge- 

 nerally take a period of twelve hours, beginning with a good 

 fire, and leaving off with the same. During this time, the velo- 

 city and temperature in the main warm air-flue should be taken 

 every half hour, and then the average of each taken, keeping 

 an account of the coal consumed in the same time. The tem- 

 perature of the outer air being also known, the excess of the 

 average temperature above the atmosphere is the datum required. 

 From the average velocity, the number of cubic feet of air 

 passing through the flue in the twelve hours may be known. 

 Put A == The number of pounds of air heated in twelve hours, 

 allowing 14 cubic feet of air to lib. 

 T =: The excess of temperature above that of the atmos- 

 phere. 

 W =: The weight in pounds of coal consumed in the same 



time. 

 E = The eflFect of the stove, which, in stoves of all sizes 

 on the same construction, should be generally a con- 

 stant quantity : Since A the quantity, and T the 

 excess of temperature, are advantages to be pro- 

 duced by W the weight of coal. 

 E, the effect, will be directly as A and T, and inversely as 



W. Therefore, £=4^. 

 W 



To give an example in practice : — A stove which is capable 

 of warming 100,000 cubic feet of space to 60° in the coldest 

 season, when placed at the depth of nine feet below the level 

 at which the warm air is discharged, will furnish about 45 

 cubic feet every second, raised 60 degrees above the tempe- 

 rature of the atmosphere. To keep up this current and excess 

 of temperature for twelve hours, it will consume not more than 

 three bushels of coals, or 2521bs. In this case, 49 cubic feet 

 of air in each second will be 1,944,000 in twelve hours, equal 



to 138,857 lbs. Hence E = ^^^'^Jo^ ^^ = 32,930. This 



