440 Mr. Joule on the Calorific Effects of Magneto-Electricity, 



I now proceeded to ascertain, by means already described, 

 the mechanical power by which the above effects were pro- 

 duced. First, I ascertained the current passing through the 

 coil of the electro-magnet ; then the weights necessary to 

 maintain the velocity of 600 revolutions per minute, both 

 when the magnet was in action and when contact with the 

 battery was broken. I have collected the results of my expe- 

 riments on this subject in the following table. The first five 

 were obtained with a battery of ten cells in a series of five ; 

 the last two with a battery of five pairs in series. 



Table IV. 



Referring to series 16, we see that 2 0, 73 were obtained when 

 the bar was revolved between the poles of the electro-magnet 

 excited by a current of 10*93. Therefore the quantity of heat 

 due to the mean current in the first five experiments of the 

 •82\ 2 



above table is 



/io_ 



\10 



9 .'5 



) 



x 2°-73 = 2°-675. To reduce this 



to the capacity of a pound of water, I had in the present in- 

 stance the following data : — 



lbs. ' lb. 



Weight of glass tube . = 1*125 = capacity for heat of 0-205 of water. 



Weight of water . .=0-687= 0-687 ... 



Weight of metallic bar = 1-688 = 0202 ... 



Total Weight = 3-500 = 1094 ... 



2 % 926, the product of 1-094 and 2°*675, is therefore the heat 

 generated by a mechanical force capable of raising 4'2 lbs. to 

 the height of 517 feet. 



