77 
the particles of magnetic bodies , &c. 
9, or in which the torsion of the wire is 9 ; and v the velocity 
of a point in the disc at the distance l from the axis of rota- 
tion ; a, 6 and v being in degrees to the radius i. We have 
therefore, vdv — m (*_ e). d6, 
v 2 = m (2 a.9 — 6 2 ), 
and t = — . vers. — . 
\m a. 
Let the values of t and 9, when v becomes o, or the disc 
begins to turn back, be t x and 6, , then we shall have 
2 « — 9 * = o , and a = Q, . 
also, t t = . 7 T , and = w . y- . 
The mean value of t x from the experiments is 269*83 seconds, 
or very nearly 270 seconds ; so that Vm = 2 . . 
We have therefore — = vers ( 2 0 . whence 
a v 3 
0 
« = r 
vers. (2 0 . — I • 
The corresponding values of 0 and t, contained in the pre- 
ceding table, being substituted in this formula, will give the 
following values of «, or of the relative forces with which 
the magnets urged the disc when revolving at different 
distances from the axis. 
Table II. 
Distance of the axes -» 
of the magnets from j. — . 
the axis of rotation J 
Inches 
4-2 
Inches 
3-7 
Inches 
3-2 
Inches 
2-7 
Inches 
2-2 
Inches 
1-7 
a 
fit 
cl 
cc 
cl 
CL ] 
1 
0 CO 
* § . 
-r *T1 
360 
720 
1080 
I 44 ° 
1800 
698-8 
688-o 
676-2 
1229-1 
1213-6 
1221-8 
1203-5 
1196-0 
1 168-8 
1642-3 
1531-6 
1538-3 
1528-9 
1518-9 
1512*0 
1498-2 
1 494*4 
* 493-5 
1589*2 
1500-0 
1491-0 
1457-0 
1423-6 
1440-0 
1409-4 
1132*1 
I 122*0 
ii 12*3 
II O47 
1098*7 
I I00-4 
641*0 
632-0 
620-9 
0 JB-o 
M'S O 
•lly 22 
2160 
2520 
^2880 
> ,c 
= 2 
0,= 
659-0 
1 1 56*3 
*394-3 
1 106-0 
600*5 
Mean values of a 
680-5 
1198-4 
15287 
1463-1 
1 1 10-9 
623*6 
