516 



REPORT 1867. 



and the thermometer and coil equivalent to 80 grains, gi\ing a total capacity- 

 equal to 98106 grains of -nrater. 12-951 divisions of the thermometer are 

 equivalent to one degree Pahr. 



The dynamical equivalent is the quotient of the work done, hy the 

 thermal effect, or 



j|-HJ'tan=0E< 



T 



r-62723 3.670731' ^ .379857 x 33435640 x 24 

 1 6-2832 J 



2400 



21-326 



=25335. 



12-951 



X 98106 



It appeared to he desirable to diminish the atmospheric influence ; I 

 therefore commenced a second series, in -which the calorimeter was covered 

 ■with two folds of cotton wadding. The bulb of the air-registering themio- 

 meter was also placed in a small bag made of the same material. In this 

 fresh series each experiment occupied one hour, as I had learned by experi- 

 ence that -with my battery arrangement the current would be sufficiently 

 uniform. In fact the highest reading in an experiment was not more than 

 ■J(^ higher than the lowest. There were, evenly distributed through the 

 hour, forty observations of deflection, twenty of the air, and three of the 

 water-thermometer ; and the water was stirred forty times. Two minutes 

 were allowed for the complete equalization of temperature previous to the 

 final thermometer reading. The experiments on radiation were also similarly 

 extended. 



The coil was the same as that used in the first series. It had a coat of 

 shellac vanish. Five determinations of its resistance were made, using a 

 single Dauiell's cell with various resistances included in the circuit. The 

 galvanometer had a coil 17 inches in diameter consisting of nine turns. The 

 results are as foUow : — 



The average temperature of the calorimeter in the experiments being 

 13°"55 Cent., and tltat at which the unit was adjusted 14°-5, the resistance 

 during the experiments must have been 1-01906, which is equal to 33434330 

 in British measure. 



