330 
If we compare the values thus found upon two different 
suppositions respecting the temperature of melting rock (one 
of them being extravagantly large) with the value for the same 
measurement as determined by estimating the actually existing 
equalities of the earth’s surface, we cannot but be struck with 
the immense discrepancy between them, the latter being from 
12 to 66 times as large”as the former. The author is con- 
sequently led to doubt the necessity for accepting Sir W. 
Thomson’s restrictions upon the manner in which the earth has 
come into its present state, especially since it seems now 
generally admitted that Bischoff’s results concerning the con- 
traction of melted rock cannot be relied upon. This was 
pointed out in 1868 by Mr David Forbes, and quite recently by 
Mr Mallet, who has determined the contraction in passing from 
a molten to a solid state to be scarcely 6 per cent., instead of 25 
per cent., as stated by Bischoff. Probably, therefore, when we 
take into account the intermediate condition of viscosity, we 
need not assume the breaking up and sinking of a crust formed 
over a molten globe. This view is supported by what Mr 
Scrope tells us about a lava-stream remaining liquid, and even 
more or less in motion in its central and lower portion for 
years’. Indeed, Sir W. Thomson is careful not to exclude as 
impossible “the case of a liquid globe gradually solidifying 
from without inwards, in consequence of heat conducted 
through the solid crust to a cold external medium.” 
If this has been what has happened, there may have been 
a much larger nucleus inclosed within the crust in early times 
than we have at present, and thus the corrugations formed 
would have been larger. And a great portion of that nucleus 
consisting of superheated rocks in a state of igneo-aqueous 
fusion, much of the water may have escaped in steam during 
the frequent volcanic outbursts of pristine ages, so that a large 
portion, at any rate, of the oceans now above the crust may have 
* Volcanos, 2nd ed. p. 84. 
