-£882.] 
Analyses of Books . 171 
duced locally within the solid shell of our globe by transformation 
of the mechanical work of compression, or of crushing of portions 
of that shell, which compressions and crushings are themselves 
produced by the more rapid contraction by cooling of the hotter 
material of the nucleus beneath that shell.” This theory is of 
the more importance, because, if we admit the hypothesis of a 
globe solid throughout, scarcely any other method to account for 
volcanic phenomena remains. The refutation of Mr. Mallet’s 
theory contributes, therefore, powerfully to overturn the assump- 
tion of the earth’s solidity, and, in consequence, Sir W. Thom- 
son’s limits to the duration of our globe. 
The first objection which Mr. Fisher brings forward, and which 
to us seems fatal, is that volcanic action is of daily occurrence, 
whilst it is unproven and strongly doubtful that such contractions 
have been constantly going on within historical times. Further, 
in Mr. Mallet’s statements, there is a serious discrepancy. In 
the “ Philosophical Transactions ” he argues that the heat 
developed from crushing ten volumes of rock would melt about 
one. whilst in his translation of Palmieri’s “ Vesuvius ” he 
estimates that the crushing of one cubic foot should melt 3^ 
cubic feet, or more than 32 times as much as his former con- 
clusion. It may certainly be said, that if this latter value is 
correct, the cubes of rock upon which he experimented ought to 
have been melted, which was not the case. There is another 
absolutely fatal objection. Suppose, taking the lower estimate, 
that the heat developed in crushing ten cubic miles of rock 
would be sufficient to fuse one cubic mile, if it could be all con- 
centrated upon that one ; it is still altogether unreasonable to 
suppose that such concentration can take place. As Mr. Fisher 
puts it “ Unless the heat got out of crushing any portion of 
rock is sufficient to fuse that particular portion, none will be 
fused.” 
The chemical theory of volcanic action put forth by Davy is 
now generally abandoned. Were water decomposed in the 
interior of the earth by contact with the alkaline metals, torrents 
of hydrogen gas would be given out, and true flame would be a 
marked feature in every volcanic eruption. It is scarcely 
necessary to say that such is not the case. 
Want of space compels us to bring our survey of this work 
to an abrupt close. It is one which may be recommended to 
young geologists and physicists, as not merely instructive but 
suggestive, and as calculated to lead to a revision of certain 
accepted theories. The considerations here brought forward, 
joined to other evidence, may lead judicious inquirers without at 
all relapsing into the coarse catastrophism of Cuvier, to doubt 
whether the opposite doctrine of uniformitarianism has not been 
carried too far. 
