354: ILLOGICAL GEOLOGY. 



assume such commencement to have been inconceivably 

 remote, as compared even with the vast eras of geology ; 

 we are not without positive grounds for inferring the in 

 conceivable remoteness of such commencement. Modern 

 geology lias established truths which arc irreconcilable 

 with the belief that the formation and destruction of strata 

 began when the Cambrian rocks were formed ; or at any 

 thing like so recent a lime. One fact from ISiluria will 

 sufllec. Sir 11. Murchison estimates the vertical thickness 

 of Silurian strata in Wales, at from 20,000 to 27,000 feet, 

 or about live miles ; and if to this we add the vertical 

 depth of the Cambrian strata, on which the Silurians lie 

 conformably, there results, on the lowest computation, a 

 total depth of seven miles. 



Xow it is held by geologists, that this vast accumula 

 tion of strata must have been deposited in an area of grad 

 ual subsidence. These strata could not have been thus 

 laid on each other in regular order, unless the Karth s crust 

 had been at that place sinking, either continuously or by 

 very small steps. Such an immense subsidence, however, 

 must have been impossible without a crust of great thick 

 ness. The Karth s molten nucleus tends ever, with enor 

 mous force, to assume the form of a regular oblate sphe 

 roid. Any depression of its crust below the surface of 

 equilibrium, and any elevation of its crust above that sur 

 face, have to withstand immense resistance. It follows 

 inevitably that, with a thin crust, nothing but small eleva 

 tions and subsidences would be possible ; and that, con 

 versely, a subsidence of seven miles implies a crust of com 

 paratively great strength, or, in other words, of great 

 thickness. Indeed, if we compare this inferred subsidence 

 in the Silur nn period, with such elevations and depressions 

 as our existing cor.tincnts and oceans display, we see no 

 evidence that the Karth s crust was appreciably thinner 

 then than now. AVhat are the implications? If, as geolo- 



