420 
MR. HARRIS ON THE ELEMENTARY LAWS OF ELECTRICITY. 
Similar results were obtained when the angle of oscillation was increased to 180° 
and upwards, as also when the weight of the cylinder P was varied from 960 to 480 
and 240 grains respectively, the radius being in each constant. The rate of oscilla- 
tion was taken with a valuable chronometer belonging to my friend Colonel Hamil 
ton Smith, and by which portions of time so little as the one sixtieth part of a second 
could be well estimated. 
Table II. 
Showing experimentally the Weight in Grains requisite to resist the reactive Force of 
the Threads at an Angle of 60°, their Length and Distance apart being varied, as 
also the Altitude of the Cylinder P (Exp. B.). 
Length. 
Distance. 
Weight in grains on a lever of 1 inch. 
P = 960 grains. 
P = 480 grains. 
P = 240 grains. 
6 
24 
| 0-25 | 
2-675 
0-67 + 
1-325 
0-325 
0-66 
0-15 
6 
1 f 
7 + 
3-525 
1-75 
12 
3-55 
1-775 
0-885 
24 
J l 
1-75 
0-875 
0-425 
24 
0-8 
6-85 
3-425 
1-750 
The smaller weights employed in these experiments could not be considered as 
mathematically exact : they were, however, sufficiently accurate for the purposes re- 
quired. They consisted of lOths of grains, 20ths, 40ths, and lOOths. The nume- 
rical values in the above Table are those which resulted from the position of the 
index, so far as these small weights could determine ; and it will be seen that the 
approximation to the values deducible from the preceding Table I., by means of the 
formula n — 
P 7T 9 a 2 
2gl > 
are as near as could be expected from such an experiment. 
Table III. 
Showing the Weight in Grains, by Calculation and Experiment, required to balance 
the reactive Force of the Threads at various Angles of Deflection from 0 to 300°, the 
Threads being 24 inches in length and - 25 apart, and prevented from collapsing by 
seven small Stays, s s' s", fig. 13, inserted between them at equal Distances (8.) ( v .). 
Weight of cylinder P = 960 grains. 
Angle of deflection. . 
10 
20 
30 
60 
90 
100 
120 
150 
180 
200 
240 
270 
300 
Force by formula . . 
•115 
•23 
•34 
•69 
1-03 
1-15 
1-38 
1-72 
2-07 
2-3 
2-76 
3-1 
3-45 
Force by experiment 
•11 + 
•22 
•34 — 
•67 + 
1 
1*1 
1-35 
1-7 
2 
2-25 
2-725 
3 + 
3-425 
