446 
MR. HARRIS ON THE ELEMENTARY LAWS OF ELECTRICITY. 
index from zero vary in this ratio, and we obtain a double, treble, &c., quantity on 
the conductor, when the index is again brought to zero of the arc x y ; a result which 
I further verified by actually placing the required quantities on the cylinder* ; these 
methods were thus brought to check each other. Immediately the index was stationary 
at o ; the charged cylinder was withdrawn from the electrometer, so as to avoid any 
possible determination of the charge toward the extremity, and the tangent plane 
immediately applied and examined by the method before mentioned ( v .), (8.). The 
cylinder was, at each successive experiment, again brought under the electrometer 
plane, and the electricity which had dissipated during the last experiment replaced ; 
the tangent bodies employed, all exposed circular touching planes of half an inch in 
diameter ; their extensions in the direction of the thickness were as follows : taking 
the letters a b c, &c., to represent the plates, and the unit of length = 1 inch, then 
a = ‘005, b = '12, c = ‘25, d = *5, e = 1, g = 2. 
In addition to these, I tried a tangent plane backed by a wire of four inches in 
length, as represented in fig. 27, and also a compound element of coated glass = q, 
fig. 8, the coatings being areas of the same dimensions as the others, viz. *4 of an 
inch in diameter, and of inconsiderable thickness. In observing these reactions the 
bodies were transferred to the balance, the disc of which was previously neutralized, 
and the electricity equally disposed upon the repelling bodies. The first deviation 
of the needle was then observed = f 3 and finally the force taken at 10° = F, consi- 
dered as a unit of distance. The square roots of the forces were then taken to desig- 
nate the respective quantities of electricity, or the ratios of the quantities existing on 
the different points of the charged cylinder. The points of the cylinder c touched, 
were the centre e, the extreme end c', and the centre of the plane face terminating its 
extremity c'. Little difference being discoverable in the points between the centre 
and extremity, I have condensed the general results of this investigation within as 
short a space as possible : they are as follows. The letters a b c, &c., denote the dif- 
ferent tangent bodies, the reactive force of the instrument being about the -^-oVo-dth of 
a grain for each degree ; f represents the first deflections, as also the distances of the 
repelling bodies ; F the reactions taken at a given distance; d = 10°; c c' e denote 
the points touched. 
Table VIII. 
Quantity of electricity = 
1 = 32° of electrometer. 
a. 
b. 
c. 
d. 
e. 
S- 
P ■ 
?• 
f. 
F. 
/■ 
F. 
/■ 
F. 
/• 
F. 
/• 
F. 
f 
F. 
f 
F. 
/•: 
F. 
c . . 
3 + 
1 — 
5 
2-5 
6*5 
4 
10 
10 
14 
25 
20 
55 
28 
168 
32 
328 
\ 
c . . 
4-5 
2 
7 + 
5 
9 
8 
14 
25 
20 
55 
29 
220 
31 
320 
32 
328 
E . . 
6 
3*5 
10 
10 
14 
26 
19 
50 
23 
92 
30 
225 
32 
323 
32 
328 
* Philosophical Transactions for 1834, p. 218. 
