180 Geological Results of the Earth’s Contraction. 
It is said that waters gain access below, and by a sudden ex- 
ion toa state of vapor, the land is thrown up: but, again, 
why should not the vast weight cause it to sink back as the va- 
rs are condensed? Surely an injection of liquid lavas into any 
cavities or opened fissures—a material that cools with such ex- 
treme slowness—would be a poor support for a chain of moun- 
tains. Is the water to gain access through opened fissures? but 
it would meet molten material rising from below to fill the fissure, 
and how then could the water thus intercepted make its way, in 
any large body, wnder the crust, so as to lift the surface into 
mountains? How can such an elevating force get beneath when 
there is no “beneath” to the fluid column short of the anti 
erust * The expansive force of contained vaporizable substances 
pent up in the liquid interior, can be a no more effectual cause ; 
for it does not appear that such a force can act against the mceum- 
bent pressure, except by making the lavas somewhat lighter and 
causing them to swell up into an opening ; it can give no eruptive 
eo ~ the igneous fluid. 
urged again that ry crust below may possibly be acquir- 
ing oii from the internal fires, so as to become elevated by ex- 
pansion. But there is little to satisfy the mind in this assumed 
possibility, especially when it is considered that through past 
times the elevation of the land has been on the whole apres = 
and yet facts and reason evince that there has also been a g 
cooling below anda thickening of the crust. With such a rane 
we should have, therefore, the incongruity of an average increase 
of heat through past ages to the present time, and a cooling of 
the crust going on, that is, a diminution of heat, at the same time. 
Tf after all, we can account for facts without calling upon any 
special force for lifting continents ;—if this effect may be a simple 
result of contraction, we are relieved of many improbable as- 
sumptions. We can well conceive that fractures should take 
——— ee 
yorkie have been so importa elevations rad me reas ’ be- 
cause we. no evidence that nah cavities ate Theslow ene end eporcnnd 
tion within produce a ped oes thickening inward ls ine ern APR yale mag 
oO ich size would form till the crust too thie 
fracturing ; and this is a gm iy which, possibly, is no garue ste hy for wer iie 
crust, even if a hun miles thick, is relative y less than a fourth the thick- 
ness of the skin of ange. 
ing of lava in a crater, Prevost eg ce significantly, loc. cit. p. 188,) “La 
ye n’est donc pas plus s ulevée par € qui serait p acée sous |’ extremite 
if a coulonne qui s'éléve af e la mousse de la bidre n'est soulevée pat 
le fond r labouteille.’’ Again, speaki ng of volcanic mountains, he per with some 
with truth, ne fawdra pas dire que ces masses sont soulevées, pas 
In a note to page 96 of this eee it was incorrectly im- 
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