228 O. U. VONWILLER. 
With the water at the temperature of the room the depth 
to which the wires were immersed was varied by increas- 
ing or decreasing the amount of water in the vessel, and 
so varying the capacity. The depth was altered until the 
deflection obtained was about the same as that obtained 
with the air condenser when its capacity was such that 
the arrangement was in its most sensitive state. The 
water was then removed and ice cold water poured into the 
vessel to the same level, and readings were taken at frequent 
intervals as the temperature rose, the temperature of the 
water being observed on two mercury thermometers, and 
the water being continually stirred except fora short time 
before sparking, when it was allowed to settle down. 
As the temperature rose, the change of capacity was 
indicated by a change in deflection. Between 0° and 15° 
there was on the whole, a decided increase in deflection, 
showing a decrease in capacity, but owing to irregularities 
in sparking it was impossible to say definitely whether the 
deflection at 4° C. was higher or lower than at 0° ©., the 
variation in successive sparks being so great as to mask 
the change between these points. 
On several occasions there appeared to be an indication 
of a minimum deflection in the neighbourhood of 4° C., but 
on other trials, apparently equally reliable, this result was 
not obtained. In any case the variation of capacity neces- 
sary to produce the apparent change would have been very 
small,—much smaller than that obtained by Thwing, which 
would have produced an unmistakeable change. 
Single sparks only were taken, the deflections obtained 
thus being more regular on the whole than those in which 
a series of sparks were taken for each observation. In 
order to obviate this variation of deflection due to the 
irregular sparking, another slider and detector were placed 
near the end of the primary circuit, and the deflections 
