398 RECENT PROGRESS IN PHYSICS. 



2. The production of heat is proportional to the squares of the fow\ 

 of the currents. 



If, therefore, t denotes the time wliich is required for the currenti 

 with the resistance to conduction I, to raise the temperature of a give! 

 quantity of spirit of wine 1° R, then s'-tl will be the time necessary t 

 produce the same amount of heat in the same quantity of spirit^ l 

 the unit of the strength of current with the unit of resistance to coi>"^ 

 duction. Since now in all the experiments the quantity of spirit < 

 wine was nearly the same, the product s-tl must also be nearly th 

 same for all of the series in the above table. The product s'^t I hei 

 the following values for the diiferent series of experiments : 

 Series. s-tl. 



1 6059 



2 5927 



3 5758 



4 5994 



5 5770 



6 5706 



7 5625 



8 5747 



9 5726 



10 5609 



11 5975 



12 6069 



13 5976 



14 6062 



15 5803 



16 5896 



Mean 5856 



The quantity of spirit heated in these experiments together witlt' 

 that of the glass, reduced by the relation of the specific heats to spirit! 

 was 118 grammes. 



The unit of the force of current produces, therefore, when passing; 

 through a wire which offers the unit of resistance to conduction, an 

 much heat as would be required to raise the temperature of \\l\ 

 grammes of spirit of wine 1° R. in 5856 minutes. 



The specific heat of the spirit used in the above experiments is 0.7 



to raise, therefore, the temperature of 118 grammes of spirit to a given 



degree requires the same quantity of heat as to raise 118.07 "=■ 82. (t 



grammes of water to the same degree. For 1 gramme of waterf 



therefore, that time amounts to : 



5856 



Q^-jT = 70.9 minutes; 



or if instead of Reaumer's scale that of Celsius is employed, 70,9 . 0,8 

 ■=. 56.72 minutes,* i. e., when the unit of the force of current passes 

 through a wire, the resistance of which is equal to that of a coppei i 

 wire of 1 meter in length and l"""" in diameter, the quantity of heat 

 produced is such as would raise the temperature of 1 gramme of watei 

 1° C. in 56f minutes. 



* In^he memoir of Lenz, an error occurs in this calculation, (P"C[. Ann., LXl, 42,) occa« 

 sioned probably by mistaking minutes for seconds. 



