Biess on Electric Currents of the First and Higher Orders. 175 



pelled to return to my old method of experiment, applying at 

 the same time a more powerful apparatus. Two flat spirals, 

 each of which consisted of 53^ feet of copper wire wound into 

 31 coils, were set one after the other in a circuit which con- 

 tained a sensitive air-thermometer. The combination of the 

 spirals with the battery and with each other was so arranged, 

 that the current could enter both at the same place (centre or 

 rim), or at different places; the directions of the current in the 

 spirals being in the former case alike, and in the latter case 

 opposite. The spirals were first placed at a distance of about 

 9 inches apart, and stood oblique to each other (the straight 

 line which joined their centres made an oblique angle with their 

 surfaces), and the following temperatures were observed. The 

 balls of the unit-jar were )> a line apart. The temperature for 

 the unit of charge is the mean value of the constant a in the 



a 2 



formula <b = a — *. 



T s 



The equality of the temperatures exhibited when the directions 



* Let q be the quantity of electricity, and y its mean density ; then the 

 time of discharge being directly as the quantity, and inversely as the den- 

 sity, will be 3- . But the strength of the current, or what is the same, its 



v 



heating power, is directly as the square of the quantity, and inversely as the 

 time of discharge; hence it is = — =«oy, where a is a constant. Further, 



y 



the density y is equal to the quantity, divided by the surface over which it 



is spread ; hence = -, when s= the surface of the battery. Substituting 



this value of y in the above expression, we have the strength of the cur- 

 ry- 

 rent, or (f>=a — . 



