404 HEXRY A. ROWLAND 



Per cent. Specific Heat between and 40 C. 



Copper 91-4 -0922 



Zinc -7 -0896 



Tin 3-6 -0550 



Lead 2-7 -0310 



Steel 1-6 -1110 



Mean -0895 



The close agreement of this number with the experimental result 

 can only be accidental, as the reduction to the air thermometer would 

 decrease it somewhat, and so make it even lower than mine. However, 

 the difference could not at most amount to more than 0-5 per cent, 

 which is very satisfactory. 



The total capacity of the calorimeter is reckoned as follows : 



Weight of calorimeter 3-8712 kilogrammes. 



Weight of screws . . . . -0016 kilogrammes. 



Weight of part of suspending wires. . -0052 kilogrammes. 

 Total weight 3-8780 kilogrammes. 



Capacity = 3-878 X '0892 = -3459 kilogrammes. 



To this must be added the capacity of the thermometer bulb and 

 several inches of the stem, and of a tube used as a safety valve, and we 

 must subtract the capacity of a part of the shaft which was joined to 

 -the shaft turning the paddles. Hence, 



3459 

 -f- -0011 

 4- -0010 

 0010 



Capacity =-3470 



As this is only about four per cent of the total capacity, it is not 

 necessary to consider the variation of this quantity with the tempera- 

 ture through the range from to 40 which I have used. 



IV. DETERMINATION OF EQUIVALENT 

 (o.) Historical Remarks 



The history of the determination of the mechanical equivalent of heat 

 is that of thermodynamics, and as such it is impossible to give it at 

 length here. 



