Experiments with the Elementary Voltaic Battery. 39 
The same after exposure of 20/ to the action of a hot solution of 
nitric acid and water in equal parts and then washed with water, gave 
No. 1 copper. No. 2 copper. No. 3 copper. 
f 135° 135° 143° 
2 134 134 140 
3 134 134 140 
4/ 134 ©. 133 139 
By reference to these tables, it will be noticed that the character 
of copper surface, as modified by various acid menstrua, is attended 
with an augmented deflecting power, and this varying with the acid 
used. 
10. When the character of surface was altered mechanically by 
filing it bright, we obtained but a slight increase of effect. 
Before filing. After filing bright. 
‘ 57° V 66° 
2 50 2’ 65 
3’ 47 3’ 65 
. On the relation of distance.—In the course of these exper- 
see we occasionally observed a variation in the deflecting pow- 
er to arise whenever we altered the distance between the zinc and 
copper, and apprehending that this did not correspond in degree, 
with the law, as announced by Professors Cummings and Ritchie, 
viz. “ That the deflection produced by a pair of plates, varies in- 
versely as the square root of the distance between them; thus if a 
plate of zinc, be placed successively at 1, 4 and 9 inches from a 
plate of copper, the deflecting powers will be in the ratio of 3, 2, 1,” 
we determined to submit the matter to experiment, and with plates 
of 8 square inches each, obtained at 
4 in. distance apart. 2 in. distance. 
5 65° sg 57° difference, 8° 
With plates of 16 sqr. inches each, 
4 in. dis. apart 44 dis. 
5 125° 5/ 95° — difference, 30° 
Plates 4 sqr. inches, 
4 in. dis. apart. 43 dis. 
a 80° 5/ 60° difference, 20° 
Repeated. 
3 in. dis. 43 dis. 
5! 78° 54° difference, 24° 
5/ 
5’ 75° 5 55° ~—Ss difference, 20° 
5/ y 
