ME. EGBERT MALLET OjST VOLCANIC ENERGY. 
205 
of work upon every ton weight of our existing globe; and as that agglomeration was 
gradual, the greater part of this enormous energy was dissipated in space as heat, and is 
the first and most enormous dissipation of energy in the formation of our planet. The 
liquid globe became gradually a partially or (for any thing we can affirm to the con- 
trary) now a wholly solid one, with a still heated nucleus. 
175. The earth’s diameter being at present 7916 British miles (adopting the coefficient 
of expansion as 933 : 1000), it was when liquid a globe 8105 miles in diameter, or at the 
temperature of incipient consolidation (supposing the whole globe ever was in that con- 
dition) 7957 miles in diameter; and if when liquid its mean temperature exceeded 
4000° Fahr., the diameter would have been still greater. 
The earth, therefore, between its period of liquidity and its present state has shrunk 
in diameter by 189 miles at the least. If we take as a rough measure of the energy 
involved in this, that it is equal to more than the work of the entire mass of the spherical 
shell of 944 miles thick dropping through 47 miles, we derive some idea of the prodigious 
energy dissipated or transformed in this second stage of our forming world. 
If we assume ^ the heat of the liquid spheroid to have been dissipated before the 
solid crust acquired such thickness as to transmit powerfully and to great distances tan- 
gential compressive strains due to contraction from that to something approaching its 
present state, that contraction represents work equivalent to 186,120 foot-tons for every 
ton of matter in the spherical shell comprehended between the radius of liquid fusion 
and the existing radius of our earth. 
176. That portion of this immense energy not dissipated as radiant heat was, as we 
have seen, consumed as work in the deformation of the spheroid, in the plication of the 
thinner crust, and in the elevations by tangential pressure of the mountain-chains. 
177. At length we arrive at the present condition of our globe, with its primitive energy 
almost exhausted, yet with enough remaining (in what comparatively is but the dregs 
or ashes) to carry on what seems to us the prodigious work of existing vulcanicity. 
178. The earth is still a cooling globe; and whether we adopt Elie de Beaumont’s 
figures (0-0065), or Thomson’s (0-0085), or J. D. Forbes’s (0-007 millimetres) for the 
thickness of the plate of ice which, covering the whole earth’s surface, if melted to water 
at 32° Fahr. would equal the heat lost annually by our globe, the result will be that from 
575 to 777/cubic miles of ice liquefied to water at 32° represents the annual loss of heat 
at present from our globe. 
179. On the assumption that our globe has cooled from a much higher temperature 
and is still cooling, it is not deniable that at the remote geological epoch when the exist- 
ing form of volcanic action began, no matter whether that was anterior to the Secondary 
epoch or when, the annual loss of heat must have been greater the further we go back 
in time, and must have exceeded 777 cubic miles per annum. 
W e shall, however, adopt Thomson’s, as probably the nearest the truth. As the latent 
heat of fusion of ice is =143° Falir., and taking the cubic foot of ice to weigh 57"6 lbs., 
we have 143° x 57-6 = S237 0 of heat in the cube foot of liquefied ice. 
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