ON THB THEORIES OP ELEVATION AND EARTHQUAKES. 53 
perature of the earth cannot be due to its original heat. Whatever then 
may be the results of experiment on this subject, they must probably lead us, 
should they be sufficiently determinate, to conclusions of the first importance 
in speculative geology respecting the state of the interior of the globe. 
17. Process of Solidiji^on comxdmi in further detail.—Ahet having 
considered generally the prot^ of the earth's refrigeration and consequent 
partial or complete solidification, let us now exatnino this process somewhat 
more in detail, from the time when the superficial incrustation began. Tliis 
incrustation may have constituted the very first step in the solidification, or 
It may have taken place alter the fonnation of asiilld nucleus surrounded by 
a superficial ttuid envelope, according us the solidification began at the sur¬ 
face or centre; but in either case, as f have already intimated, the super¬ 
ficial crust when first formed must necessarily have reposed on a fluid mass 
beneath. Let us conceive a thin iucrustaiion to have been formed; the 
escape of the clastic gases would then be arrested, and their tcnslun would 
wnsequently increase, till their elastic force should be sufficient to rupture 
the cou^uing crust. Thus refrigeration would constantly tend to augment 
Me thickness and strength of the crust, while the elastic vapours would tend 
to break it up. and, so long as the crust remained sufficiently thin, innume¬ 
rable dislocations would probably take place, but without leaving any dis¬ 
coverable traces behind them, on account of the dislocated mu*c 3 , unlike 
stratihed beds, having no character to indicate timir original undisturbed 
positions. As the residing power of the crust iiicreiwed, and the elastic power 
of the gases diminished in consequence of diminished temperature, it would 
require longer periods of time for that accumulation of the vapours w liich 
■would be necessary to give tbem elevating force sufficient to raise and dislo- 
cate the superincumbent crust. Ily the action of irregular cauMs, some por- 
lODs ot the crust would doubtless become more compact and unbroken, and 
others more dislocated ; so tbat while the former might be able to resist the 
ettortsol the elevnling forces, the latter might long remain subject to re¬ 
peated disturbance and fracture. Moreover, when this distinction between 
Uie more tranquil and mow; disturbed portions of the solid crust should have 
ocen once established, other causes also would tend to perpetuate it. For 
e dislocated portions, while the crust was comparatively thin, would doubt- 
ess contain many internal cavities, some of which would form receptacles 
mr elastic vapours, and others by their communication with elm external sur- 
aw would act as volcanic vents; anil thus the internal vapours would ascend 
wi more active energy beneath the fractured portions of the cnist than 
under those which remaiued comparatively unbroken. The gaM S formed 
enea h the unbroken crust would, in part at least, ascend obliquely towards 
tne regions of easier twnpc, and thus while they would luavo ihe upper part 
01 Uie fluid mass imniediatoly beneatli iho unbroken parts of the crust in 
comparative repose, they would assist In keeping the fluid mai» under the 
aisJocated portions of the crust in a state of greater ebullition. Under such 
circuiastances, it is manifest that the. solidification would proecerl more 
*®pi y beoeatli tlie undisturbed than beneath the disturbed portions of the 
®ust, and the tendency would be to iocreosc and perpetuate the distinction 
tween them as above asserted. Moreover the eruptions of a paroxysmal 
c aracter, which, it may be presumed, would take place from time to time. 
Would not only produce a temporary interruption of the procc«8 of solidifica- 
on, but would also destroy by a great disturbance of the mass in which it 
* ould occur, much of wliat might have been effected in the incipient stages 
01 the process during, a previous state of repose. 
Ihe more rapid iucrease of thickness in the more undisturbed portions of 
