20 PRINCIPLES OF GEOLOGY. 



having learned to agree upon facts, have ceased to dispute about opinions. 

 The time is come when the observers of nature have imbibed a spirit of 

 calm and limited induction, which leads to candid agreement or modest 

 dissent. 



No one can doubt that great alterations were occasioned in the 

 features of the earth's surface, at the period of the deluge, who considers 

 the extensive tracts formed of the diluvial detritus. All the solid land of 

 Holderness is an accumulation of this kind, from the ruins of other parts 

 of England and Scotland, and perhaps Norway. If hills were known 

 before the flood, their present peculiar shapes must be dated from that 

 event ; and if vallies were then in existence, they must have been 

 deepened and widened, or possibly filled up and obliterated. But that 

 the whole antediluvian surface of the world was even and uniform, is 

 altogether improbable. For, to a very considerable extent, the great 

 features of the earth's surface are determined by peculiarities in its in- 

 ternal construction. Its highest ranges of mountains are composed of 

 one set of rocks, but its widely extended plains are based on another. 

 Obviously, therefore, these great distinctions are not only antedilu- 

 vian, but aboriginal. There are, also, many lesser features of this 

 kind, which must be carefully selected from the phenomena ascribed 

 to the deluge. Many great natural depressions or wide vales are 

 produced, evidently by the convergence of opposite declinations of 

 strata ; as the great vale of the Thames is occasioned by meeting dips 

 from Hertfordshire and Surrey ; and such are, doubtless, antediluvian. 

 Many geologists believe that, from some unexplained causes operating 

 during their deposition, some strata were originally deposited at higher 

 elevations than others ; that, for example, the lower part of the coal series 

 was made to attain elevations not reached by the upper part of the same 

 series ; and that the new red sandstone was never in England placed at 

 so great an altitude as some of the strata which lie above it and below 

 it. In these instances, therefore, it has been concluded that the ante- 

 diluvian features of the earth were not very different from what we now 

 witness : and these instances admitted to their full extent, actually 

 include the most striking variations in the surface of the earth ; for it 



