170 
MR. SNOW HARRIS ON THE SPECIFIC INDUCTIVE CAPACITIES 
Table II. 
Showing the Specific Inductive Capacities of various Electrical Bodies in terms of 
the number of measures condensed by them on an accumulation of five measures. 
Substances. 
Lac. 
Brimstone. 
Flint glass. 
Bees’ wax. 
Pitch. 
Rosin. 
Air. 
Inductive capacity 
O 
4-3 
4-25 
4-21 
O 
4-1 
O 
4 
O 
3-9 
2-2 
14. If, then, as in the preceding Table, the number of charges condensed by the 
indirect induction of the uninsulated coating be taken to express the respective in- 
fluences of different dielectric substances over the induction through them, we have 
the relative inductive capacities as in the following Table. 
Table III. 
Showing the Inductive Capacities of various dielectric Bodies in relation to Air 
taken as unity. 
Substances. 
Air. 
Rosin. 
Pitch. 
Bees’ wax. 
Glass. 
Brimstone. 
Lac. | 
Relative capacity 
0 
1 
1-77 
O 
1*8 
1-86 
O 
1-9 
1*93 
1*95 
The results in the case of lac and air very nearly coincide with those arrived at by 
Dr. Faraday, who found (1270.) the relation of lac to air as 2 : 1 , or very nearly, 
which is about the proportion deduced in the above Table. He also found a very 
high inductive capacity for sulphur, which is likewise the case in the above Table, 
although the specimen employed in these experiments did not give a higher capacity 
than lac, as appeared to be the case in the experiment Dr. Faraday refers to (1275.), 
and which he considers unexceptionable. With respect to glass and the other sub- 
stances above given, all the specimens insulated well, and charged and discharged 
freely in the usual way. The experiments were certainly uninfluenced by the sources 
of error above-mentioned (2.), since the intensity varied with the square of the 
number of charges deposited on the insulated coating, and the general laws of elec- 
trical accumulation on coated surfaces were manifested by them, which could not 
have been the case under a sensible degree of conducting power, or a partial absorp- 
tion of electricity by their superficial particles. Thus I found a square of thick plate 
glass of the common kind, and which the Lords Commissioners of the Admiralty very 
kindly permitted me to purchase from the stores of Her Majesty’s Dock Yard, quite 
unfit for these investigations. It would not take the slightest degree of charge under 
any condition under which I could place it. By covering its exposed edges with 
shell-lac dissolved in naphtha or alcohol, I succeeded in rendering it non-conducting 
on the surface, but still it would not assume the charged state in any degree. I tried 
other specimens of plate glass, and with nearly the same result. And it was not 
