16 M. L. A. Colding on the Universal Powers of 



The degree of heat developed in a fluid by one atmosphere of 

 pressure will in general be a function of the temperature of the 

 fluid. If, for example, we take distilled water and suppose its 

 specific heat to be unvaried at all temperatures, then, according 

 to formula (28), we get, at the temperature T', 



and at the temperature 0°, 



D' 3 . C0 



D' and e' denoting the values of D' and e' for T' = 0°. 

 Whence, consequently, follows 



IT' 



which shows that for water the degree of heat developed varies 

 so little that, on the whole, it may be considered constant. 



Conformably to formula (20), we may now easily determine 

 the amount of mechanical energy equivalent to the unit for 

 quantities of heat, as one unit of heat raises the temperature of 

 1 pound of water 1 degree Celsius ; for this formula may be 

 written 



co~gmh(aY ) — '-— j 



as we notice that, when the volume for the said unit of mass of 

 air at 0° under the pressure gmh is denoted by V , then 



But now 



D V =I 



_ °' 76m - 13 -5 98. 62 pounds § 

 gmh— 1728 ' 



and if the mass of one pound of air is taken as unit, then is 



_ 0-00366.172 8 

 °~ 0-001299. 62 ; 



7 = 1-407 and 0'76 metre =2*421 feet, 



w = 321-42 pounds; ...... (32) 



which shows that when mechanical energy, expressed by 1 pound 

 raised to the height of 321'42 feet, is imparted to one pound of air, 

 then the internal energy of the air will be increased in such a manner 

 that its temperature must rise one degree Celsius. If the specific 

 heat of the water is denoted by co p then, in conformity to De la 



also 



whence follows 



