DIELECTRIC CONSTANT OF WATER AT LOW TEMPERATURES. 233 
In all these curves there is to be noticed a decided fall 
in capacity as the temperature rose, and the curve is prac- 
tically a straight line. | 
The. change of capacity for 1° rise in temperature, ex- 
pressed as a percentage of the capacity at 0° C. obtained 
from these different curves is, in Fig. 3, 0°464; Fig. 4, 0°478; 
Fig. 5, 0°287; Fig. 6, 0°344. 
The dielectric of the condenser consisted partly of water 
and partly of air, the wires being out of the water for a 
considerable part of their length, and as the variation 
affected only the water, the total percentage change of 
capacity is less than the actual change in the dielectric 
constant of the water. 
In the first two trials recorded above, the water was 
placed in a large glass vessel 25 cms. square, and the depth 
of water in it was about 15 cms., but inthe other two, the 
water was placed in a beaker 15 cms. in diameter, and the 
depth of water was about 15 cms., so in this case the air 
would have a greater relative share in the whole effect, 
and so the observed variation is less than in the former 
trials where the variation in capacity is probably very 
nearly equal to the variation of the dielectric constant of 
water. In all four trials the wires were immersed to a 
depth of from 5 to 6 cms. and were from 9 to 11 cms. apart. 
The assumption has been made, that, when the same 
deflection is obtained with the water and air condensers, 
the capacities are the same. By removing water from 
the vessel and so decreasing the capacity, we can come 
into a position of resonance, and it was found that on doing 
so the maximum deflections obtained were practically the 
Same as the greatest deflections obtained with the air 
condenser, and so the conductivity of the water has no 
appreciable effect, and the above assumption is probably 
P—Dec. 2, 1903. 
