Page:Scientific Memoirs, Vol. 1 (1837).djvu/631

periments as from those of Biot, that the action of a particle of the electric currents which encircle the magnet upon every particle of the spiral, is in the inverse ratio of the squares of the distance.

It also immediately follows from the law just demonstrated that the electric current produced in the various wire rings which inclose the armature, by its removal from the magnet, is in the inverse ratio of the diameter of the rings; for the electromotive power is the same in every ring, but the resistance it suffers in being conducted increases as the diameter of the rings; therefore the electric current, the quotient of the electromotive power, by the resistance it suffers, decreases as the diameter of the rings increases.

III. Influence of the Thickness of the Wire of the Electromotive Spirals on the Electromotive Power produced in them.

I have also again made these experiments with the horseshoe magnet, since in this case the convolutions of the wires had always the same magnitude. I here employed ten convolutions, which I formed from the wires No. 1, No. 3, and No. 4, and in which the diagonals were in the same proportion as the numbers 233 : 839 : 1661. The entire length of the convolutions in each sort was 33 inches. The deviations are contained in the following table.

	Angle of deviation.				Mean.
	1	2	3	4
Spirals from No. 1.	39·3	40·4	35·1	37·8	38·15	38·19
	39·3	40·4	35·2	38·8	38·22
Spirals from No. 3.	36·8	39·6	40·2	42·0	39·65	39·60
	36·4	39·4	40·4	42·0	39·55
Spirals from No. 4.	40·5	42·4	37·5	39·3	39·92	39·74
	40·3	40·4	37·5	40·1	39·57
Spirals from No. 1.	38·6	40·6	35·7	37·8	38·17	38·00
	38·7	40·0	35·2	37·4	37·82

If we now combine the observations No. 1, at the beginning and end of the series of experiments, and take their mean, we have the following deviations:

For	No. 1	the deviation	or	$\alpha \;\,{}=38.1$,
—	No. 3	————	or	$\alpha '\,=39.6$,
—	No. 4	————	or	$\alpha ''=39.7$.

From the proportion of the diagonals in which that of the wire of the multiplier is expressed by 274, we find the following reduced lengths (referred to the wire of the multiplier or No. 2) of our three spirals,