24:4: THE GEOLOGIST. 



clue may be obtained which will serve to iiuravel something of the 

 history of those extensive denudations which have given origin to the 

 curious iutercircling, and often perplexing, assemblage of mesozoic and 

 ancient rocks which is presented by the geology of this part of South- 

 western England, — where, although organic remains are by no means 

 abundant, the fossil-collector may, at the end of a day's search, lay 

 side by side the characteristic indices of life-periods separated by vastly 

 remote interv^als of geologic time, gathered out of not more than half- 

 a-dozen quan-ies, in the space of as few miles, — and w^here, in a 

 country that hardly deserves to be called hilly, the petrologist may 

 note, in an area of the same or even less extent, an individually- 

 represented range of formations, from " old red " to " lower lias." 



By such restorations of the breaks and euiTes in the limestone, it 

 becomes at once apparent th^t an enormous amount of mineral matter 

 has been destroyed and re-arranged. The coal-measures, with their 

 coal-seams " cropping " nearly to the surface, and actually coming out 

 to the day in places, afford perfect evidence that their collection of 

 shales and sandstones were never originally discontinued at their 

 present outcrop, but that, on the contrary, they form only the remnant 

 of a more extended tract of similar strata, long since destroyed, that 

 once covered the subjacent limestone. The efevated portions of 

 this rock, together with the old red sandstone, formed islands and 

 headlands, exposed to the action of breakers which, w^hile they beat 

 away the cliffs of the coal-measures, furnished from the harder 

 strata those sub-angular shingles which, with the limestone-pebbles, 

 were afterwards cemented and consolidated by a calcareous or mag- 

 nesio-calcareous paste, into the dolomitic conglomerate. That this 

 conglomerate was in part derived from these strata, is attested by the 

 fact, that as the beds approach the coal-measure&, the quantity of 

 fragments of sandstone preponderates over those of limestone. It 

 is also fixir to assume that the softer rocks may have furnished the 

 patches of red sands and marls afterwards thrown down in quiet 

 places on the conglomerate. In a quarry near Pyle, about three 

 miles from Newton Nottage, a section can be observed, where 

 these red sands and marls rest on the denuded surfaces of the conglo- 

 merate, and are surmounted by lower lias-limestone. 



In Sir H. De La Beche's valuable paper on the " Formation of Rocks 



