MR, ROBERT MALLET ON VOLCANIC ENERGY. 
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which, divided by the cubic yards in one cubic mile, 1760 3 , or 
9770662000 000 =1792 cubic miles 
5451776000 
of crushed rock to produce the whole. 
The lost heat (in crushed rock) of our globe could produce this amount in less than 
two years. But such an eruption as the above does not occur probably in a hundred 
years, if such an eruption ever occurred at all. 
But that is only the ro w? P ai 't °f the equivalent in mean crushed rock of the heat at 
present lost annually by our earth, which, as we have seen, is equal to 777 cubic miles 
of ice melted, or to 987 cubic miles of mean rock if crushed (992 cubic miles if we 
take the weight of a cubic foot of ice at 57*8 pounds).] 
The volume of rock necessary to be crushed annually as thus found is (as in the 
former estimate) perfectly insignificant, when compared with that of a solid crust of 
800 miles thick or even of 100 miles in thickness. 
199. Finally, it is apparent that even were our estimates of past or of existing volcanic 
energy of our globe below the truth to such an extent that ten times the estimated 
amount of crushed rock would be needed to supply it, we should still have an ample 
storehouse of energy for it in the heat now annually lost by our globe, leaving still the 
greater part of that to be wasted by radiation into space. 
200. The rock thus crushed transfers a portion of its own mass from a greater or less 
depth to the surface, and frees the cavities from which it is ejected of so much bulk, 
permitting them thus to close in and accommodate the dimensions of the shell to those of 
the shrinking nucleus beneath ; but the mass is only transferred, it is not lost ; and the 
transfer might have no effect whatever on the length of the day, even were its mass far 
greater. 
Nor is the volume of rock crushed (to perform the volcanic work) necessarily all 
ejected ; from any one point, on the contrary, much of it may cool again in situ with 
extreme slowness, and get recompacted into solid rock. 
201. The writer believes, however, that a considerable proportion is ejected, and that 
this is, in fact, the function or final cause in the cosmos of vulcanicity. It is the means 
whereby a contracting solid crust gradually, and, though paroxysmally, on the whole 
harmlessly, adjusts itself to the dimensions of the nucleus shrinking away from beneath 
it ; and were it not for this provision in the grand machine, or were the solid crust so 
rigid and constituted that its parts could not locally crush up, and the crushed matter 
be cleared out and thrown up to the surface, prodigious paroxysmal convulsions must 
result, with perhaps ages intervening between them, which would probably overturn 
the whole economy of the surface upon which the existence of organized life is now 
dependent. 
Admitting fully within what wide limits of error estimates such as these alone 
admit of being made, the writer yet submits that he has proved to a high degree of 
probability that 
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