copper and other substances during rotation. 
Disk C, weight =: 2724 grains. 
507 
Screw. 
Unscrew. 
Distance. 
Unscrews. 
Arc of torsion = force. 
Screws. 
Arc of torsion = force. 
Arc. 
Time. 
Vel. 12 . 
Vcl. 24. 
Arc. 
Time. 
Vel. 12. 
Vcl. 24 . 
0.6 
1 . 1 
1 .6 
2.1 
2.6 
0 
7270 
3465 
1670 
700 
308 
in. s. 
1 44 
I 42 
I 40 
I 39 
I 38 
0 
3642 
1770 
834 
347 
184 
7750 
3380 
1456 
680 
320 
m. s. 
1 43 
I 40 
I 40 
1 39 
» 39 
3874 
1680 
726 
354 
180 
It is evident from these results, that the force with which 
the magnets urge the disk, as the distance increases, de- 
creases much less rapidly than in the case of the copper 
plate revolving. If we suppose it to vary as then 
calling c and c' two distances and T and T' the correspond- 
ing torsions, which are equal to the forces of the magnets. 
n = 
log. log. 
log. c ' — log. c * 
Comparing the preceding results, the several values of n 
will be. 
Values of n 
Disk A. 
Disk C. 
-1.723 
1 .285 
1.995 
1.556 
2.087 
1.864 
2.271 
2.065 
2.436 
2.118 
2.429 
2.406 
2.658 
2.614 
2.420 
2.803 • 
2.831 
2.998 
13*354 
3.246 
These differ too widely from each other for us to suppose 
that the force varies as any exact power of the distance ; 
MDCCCXXV. 3 U 
