24 Mr Wilberforce, On Specific Inductive Capacity. [Oct. 25, 
by m, and the depth of the substratum measured by n, were so 
related that m was the reciprocal of log.(1+ 2), there would be 
“no tide in the substratum, as for instance if m were about 0°91 
and the depth to the solid core 50 miles; or m=0°72 and the 
depth about 100 miles; or m= 0°62 and the depth about 150 miles. 
These numbers show that, if the solubility of the gas in molten 
rock was analogous to that of carbonic acid in water or of sul- 
phuretted hydrogen in water; and the depth somewhere between 
50 and 100 miles; scarcely any tide would be raised in the sub- 
stratum, for the effect would consist merely of a change in the 
vesicularity of the magma following the tide-raising body. 
The vesicles of gas liberated during the passage of the body 
being extremely minute would not have time to rise through the 
liquid before they were redissolved by the recurring pressure. 
It appears therefore that the hypothesis may possibly account 
for the absence of bodily tides in the earth, and thus remove the 
chief objection to a liquid substratum. 
If from any cause the pressure upon the surface of the sub- 
stratum were to be permanently lightened, as for instance through 
denudation or any other cause, the liberated gas would not be 
redissolved, but the liberated vesicles would coalesce and rise 
through the magma, expanding as they reached regions of dimi- 
nished pressure. Thus the expansion of the column would exceed 
that given by our formulae, which contemplate the vesicles re- 
maining stationary where they are formed. But in spite of the 
small relative density, it is possible that viscosity would consider- 
ably retard the upward movement of the vesicles in their incipient 
state. It appears therefore that when we come to add the expan- 
sion due to the enlargement of the rising vesicles it would exceed 
the denudation. It seems possible that this may have a bearing 
upon the direct elevation, without plication, of plateaus like that 
of Mexico or the Colorado, which is supposed to be connected with 
volcanic action. 
(3) On a new method of determining Specific Inductive 
Capacity. By L. R. WILBERFORCE, B.A. 
( Abstract.) 
The author briefly described the method, which consisted in 
the comparison of the directive couples upon two spheroids, the 
one made of the dielectric to be investigated and the other of some 
conducting material, when they were placed in a uniform electric 
field. He further indicated certain theoretical considerations with 
regard to the eccentricities of the spheroids and their manner of 
suspension, and stated a general theorem relating to the mechani- 
cal effect due to such a field upon a body of any material or form. 
