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 has established truths which are 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 time. One fact from Siluria will 

 suffice. Sir R. Murchison estimates the vertical thickness 

 of Silurian strata in Wales, at from 26,000 to 27,000 feet, 

 or about five 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. 



Now 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 Earth'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 Earth's molten nucleus tends ever, with enor- 

 mous force, to assume the form of a regular oblate sj^he- 

 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 Silurian period, with such elevations and depressicna 

 as our existing continents and oceans display, we see no 

 evidence that the Earth's crust was apjoreciably thinner 

 tben than now. What are the implications ? If, as geolo- 



