

Constant of Water at Low Temperatures. 6959 
5, being the deflexion produced by the detector in the 
primary, and 6, the deflexion produced by the detector in the 
secondary. 
Accordingly, in subsequent experiments the deflexions 
produced by detectors in both primary and secondary were 
taken after each spark, and the variation of the ratio of the 
two observed. 
These experiments all indicated a continuous fall in 
capacity as the temperature rose, at least no marked critical 
point at 4° C. being shown. 
In order to ascertain the extent of the change of capacity, 
a condenser consisting of two circular brass plates, 30-2 centi- 
metres in diameter and ‘755 centimetre thick, which could 
be moved apart in a direction perpendicular to their planes, 
was substituted for the water condenser, and observations 
were taken with the plates at different distances apart. The 
capacities at these distances were calculated by Kirchhoff’s 
formula : 
a} _1l6ar(a+d) a+d\* 
Bee ff oeonc GED sg 4} 
where 7 is the radius of the plates, a their distance apart, and 
Fig. 2. 
1400 
130 - 
St 
1000 
bs i 
Se ae ae ee 
S300 | 
at ae wera 
700 
ey ree ee 
ihr fu Re ibe aga 
pee he 
ania cdl 
hy i Ss ge ed 
ET FS Oe Vee? Tia We, re ee 
Capacdy. 
d their thickness ; and the resulting curve between capacities 
and the ratio 10002 6,/6, is shown in fig. 2. This curve 
* Abhandl. p. 112. 
2Y 2 
Qo 
© 
(=) 
