CAPACITY OF GLASS, AND OF LIQUIDS. 
3G5 
Charge to each condenser 
in Ag.Cl. elements. 
10 
100 
200 
300 
400 
500 
Capacity in millim. divisions 
of sliding condenser. 
27375 
274-00 
273- 75 
274- 5 
273-0 
273-5 
The mean of these is 273-75, and the greatest variation from the mean 0 - 28 per 
cent. 
The conclusion has some considerable importance, for some conceivable molecular 
theories of specific inductive capacities would lead to the result that capacity would 
be less when the charge became very great, as is actually the case with the magnetic 
permeability of iron [vide Maxwell, vol. ii., chapter vi.). 
The flasks tried are about 1 millim. thick. I intend to try a very thin glass bulb, 
testing it to destruction. 
[In order to extend the limits of this test, a thin bulb 29 millims. diameter was blown 
on a piece of thermometer tube and its capacity compared with the sliding condenser 
with varying charge, as follows :— 
100 battery elements to each condenser, capacity of bulb was 297 scale divisions. 
300 elements, capacity =297 divisions. 
500 elements, capacity=2971? divisions. 
The bulb was afterwards broken and the thickness of the fragments measured; 
they ranged from 0"05 to 0"15 millim., the major portion being about 0"1 millim. We 
may conclude with confidence that the value of K for the glass tested continues 
constant up to 5000 volts per millimeter.—Dec. 9, 1880.] 
An experiment was subsequently tried to ascertain if specific inductive capacity 
varied with the temperature of the dielectric. Accurate results could not be 
obtained, owing to the expansion of the acid, causing it to rise in the neck of the 
flask. The result of the single experiment tried was, however, that the flask at 
14° C. had a capacity equal to 275 divisions of the sliding condenser; at 60° C. it 
was equal to 280 divisions. Having regard to the increase of capacity due both to 
the expansion of the glass (which may safely be neglected) and to the expansion of 
the acid (which is material), we can only conclude that the capacity of glasses cer¬ 
tainly does not change rapidly with tempei'ature—that consideration of temperature 
cannot be expected to reconcile Professor Maxwell’s theory with the results of 
experiment. 
I have repeated the temperature experiment with greater care. The flask was 
cleansed, filled a little short of the shoulder with acid, and arranged for heating 
and testing as before. In order to avoid the effect of rising of the level of the acid 
from expansion, the flask was heated to its highest temperature before any observation. 
3 b 2 
