ME. EOBEET MALLET ON VOLCANIC ENEEGX. 
161 
sink to the centre of the liquid spheroid, and remain there still solid, and so gradually, 
of such fiery debris, build up a honeycombed but solid nucleus, with liquid matter above 
it and a solid crust above all. When we take into account the excessive relative 
thinness of the original solid crust, a very few miles, perhaps only a few fathoms, and 
the small volume of its mass in comparison with the enormous volume of the liquid 
nucleus, through which the fragments of crust have to descend some 4000 miles, 
together with the enormous excess in temperature of the liquid approaching nearer the 
centre, it seems impossible to arrive at any rational conclusion, except that such 
sunken sheets of solid crust must be reduced to liquid fusion again by heat conducted 
into them from the heated liquid, the local temperature of which would be increased 
by heat generated by their fall through the liquid a distance nearly equal the earth’s 
radius before they ever reached the centre ; and assuming that the laws of gravitation 
within a spheroid, and the density of the crust and relative rate of compression with 
depth of the crust and of the liquid, would ever permit them to reach that centre, 
Poisson’s hypothesis, which has been a stumbling-block in the way of more rational 
interpretation of these difficult questions of primaeval geognosy, should, the writer 
submits, be set aside. 
51. In cooling bodies, as the loss of heat in equal times is greater the greater the 
difference in temperature between the hotter and colder bodies, the rate of cooling of 
the globe, when its general temperature must have exceeded that of our hottest furnaces, 
and when, as we must presume, that of the celestial spaces was the same as now, must 
have been very rapid. The amount of contraction also (aided as the cooling rate 
was by the circulatory currents within the liquid before referred to) must have been 
proportionally rapid. 
52. The viscous crust must be supposed greatly thicker than the solid sheet above it. 
The enormous amount of rapid contraction at this period was, in the writer’s opinion, 
met by that deformation of the spheroid which hollowed out the ocean-bed to very 
much the general outlines that we now see, and so assigned the general forms to the 
continents. 
This cannot be viewed at present as much more than a conjecture; still it is one not 
without support both from authority and from facts. It seems impossible to assign any 
other machinery or one adequate in force to a soulevement or subsidence so vast, extending 
unbroken over such vast areas, and which should give to the sections of both land and 
ocean-bed their actual forms, which (without regard to mountain and valley) are but 
vast flat, raised-up plains, dipping more or less abruptly down to equally shallow, flat, 
saucer-like plains of ocean concavity. Lateral thrust or radial pressure at local centres 
seems here equally inapplicable. It is for the physical astronomer to investigate the 
causes of this very striking and obviously not chance-configuration of this deformation 
on the surface of our globe. [It should also be remarked that a certain order in the 
form of the land (coast-lines) and sea indicates that these are not the mere result of 
superficial actions, such as deposition, denudation, and local oscillations of level, but 
