Page:American Journal of Science, Series 2, Volume 9.djvu/15

Prof. Loomis on Electricity of Zinc buried in the earth. 5

No. of Experiment. Size of the Copper Plate.

Copper surface immersed.

Deviation of Galvanometer.

Tangent of deviation

14 48 inches by 14 1354 square inclies. 74|^ 3-6(JS 15 24 " 14 682 " 7li 2-989 16 12 " 14 346 68i 2-507 n, 6 « 14 178 C6.i 2-300 18 6 « 9 94 « 64| 2-120 19 3 « 7 52 62i 1-921 20 3 « 3i 31 601 1-786 21 3 " 2 22 59 1-664 22 3 « 1 16 « 57 1-540 23 3 « i

Length of wire immersed

13 56i 1-511 24 6 feet. 10 8 " 66 1-483 25 5.J " 9-9 55J 1-442 26 3 « 5-4 461 1*003 27 1 « 1-8 32| •643 28 6 inches. 0-9 « 19 •344 29 3 " 0-45 11 •194 The law which these numbers follow is exhibited by the following curve, in which the abscissas represent die amount of copper surface immersed in the water, and the ordinates represent the intensity of the electric current, assuming the intensity to be proportioned to the tangent of the angle of deviation of the galvanometer.

The numbers below the horizontal line represent the square inches of copper surface immersed: the dotted vertical lines represent the corresponding intensity of the electric current. Thus it appears that for plates less than one square inch, the intensity of the current as measured by its effect upon a magnetic needle, is nearly proportioned to the surface of the plates; but in order to double the intensity of the current yielded by a