106 J, LeConte—Structure and Origin of Mountains. 
paper. But, let it be borne in mind that it is no olyection at all 
to the contractional theory, — only to that — of it which assumes 
the complete solidity of the earth. There can be no difficulty in 
the way of concentration ‘of the effects were interior contraction 
along certain lines so as to give rise to mountain ranges, if the 
earth be liquid beneath a solid crust, as maintained by some; 
or if there be a layer of aqueo-igneously fused or semi-fused 
matter between a solid crust and a solid nucleus,* as maintained 
by many of the very best geologists. To the idea of a sub- 
stantially liquid earth covered only with a thin solid shell, I 
elieve there are insuperable objections; but the existence of 
a layer of semi-fused matter would not interfere with the sub- 
stantial solidity of the earth in all its cosmical relations. ‘The 
but only large areas of the crust thus underlaid. These areas 
are undoubtedly the ocean beds which, as we have already 
said in our previous paper, are the most contractile portion 
second objection urged against the contractioual theory 
is this: the amount of contraction produced by secular loss of 
heat, it is said, is wholly inadequate to produce the foldings 
which we actually find, being in fact demonstrably very small. 
Now assuming that, in so complex a problem, all the data are 
correct and the reasoning logical (a large assumption, when we 
remember the difference of views among the best physicists on 
some geological Laing and the frank admission of grave 
error, Tecentl by one of the most eminent),+ allowing I say 
the objection its fall perro and all the certainty claimed for 
it; still it is evident that this is no objection at all to the contrac- 
tional theory ; but, again, only toa particular form of that theory, 
viz: that which assumes the contraction to be the result solely 
of loss of heat. This, it is true, has seemed the most obvious 
cause of contraction. It is certainly a true cause even if it be 
not by itself a sufficient cause. There are, however, other causes 
of contraction conceivable, and perhaps still others not yet 
dreamed of. Other things besides the earth shrink and shrivel, 
and in some cases without loss of heat. Apples shrivel by 
loss of moisture, and old people’s faces wrinkle for the same 
reason. Now is it not barely possible that there may be other 
causes of a ot the earth and the wrinkling of its face, 
besides loss of hea 
It is well are ‘us immense quantities of gas and vapors, 
especially steam, issue from volcanoes. This steam is usually, 
and perhaps truly, supposed to be derived from above—to be, 
* Fisher, Phil. Mag. -y VOL LD. Ont, 15 
a <7: m. Thomson’s Address, before ‘Britich Association, 1876. This Journal, 
ii, 
