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



The heat evolved from the whole circuit by such a current is 



/1*483\ 2 



\!Fl45/ X 5 °' 88 * 1,3 ° 3 X 1,114j = 4, ° , ° 8 per lb# of water 



per 15 minutes, according to data previously given. Hence 



the quantity of heat due to the chemical reactions in the ex- 



1*955 

 periment is x 4°*08 = 5°*38, instead of 9°*92, the quan- 



tity actually evolved. 



Hence 4° 54' were evolved in the experiment over and above 

 the heat due to the chemical changes taking place in the bat- 

 tery, by the agency of a mechanical power capable of raising 

 7 lbs. 8 oz. to the height of 55 1 feet. In other words, one de- 

 gree is equivalent to 910 lbs. raised to the height of one foot. 



An experiment was now made, using the same apparatus as 

 an electro-magnetic engine. The power of the magnetic at- 

 tractions and repulsions alone, without the assistance of any 

 weights, was able to maintain a velocity of 320 revolutions per 

 minute. But when the circuits were broken, a weight of 1 lb. 

 2 oz. had to be placed in each scale in order to obtain the 

 same velocity. The deflection of the needle was in this in- 

 stance 17° 15' = 0*63 of current electricity. The perpen- 

 dicular descent of the weights was 275 feet per 15 minutes. 



Now, calculating in a similar manner to that adopted in the 

 last experiment, we have, from series 9, Table II., and other 



(630\2 

 — ) X 0°*50 x 1*303 = 0°*877, 



which, on applying a correction of 0°*012 on account of 

 sparks at the commutator, and o, 18 on account of the iron of 

 the revolving electro-magnet, and then reducing to the capacity 

 of a pound of water, gives 1° # 191 as the quantity of heat 

 evolved by the whole circuit in 15 minutes. 



The quantity of current which the two cells could pass 

 through the revolving electro-magnet when the latter was 



/1'538\2 

 stationary, was in this instance 1*538 ; and f j x 5°*88 



x 1*303 x 1*114 = 4°*38. Hence, as before, the quantity 

 of heat due to the chemical reactions during the experiment is 



^f- x 4°*38 = 1°*794, which is 0°*603 more than was ob- 

 1*538 



tained during the revolution of the electro-magnet. 



Hence 0°*603 has been converted into a mechanical power 



equal to raise 2 lbs. 4 oz. to the height of 275 feet. In other 



words, one degree per lb. of water may be converted into the 



mechanical power which can raise 1026 lbs. to the height of 



one foot. 



