58 PICTURESQUE SKETCHES 



strata of the Silurian period; and from this deposit 

 are obtained occasionally the fossil remains of fishes of 

 the same species as those found in Scotland. 



Lastly, in Devonshire and Cornwall, between the 

 granite of Dartmoor and a series of black strata of 

 the same geological age as the carboniferous beds 

 which elsewhere overlie the conglomerate of Hereford- 

 shire and Scotland, there is a large series of sandy 

 and slaty rocks, containing numerous fossil shells and 

 other organic remains ; and these appear, on exami- 

 nation, to possess a character intermediate between 

 that of the silurian and that of the newer or carbo- 

 niferous series. 



Now it will be readily admitted, that a sea in which 

 the coarse, gravelly conglomerates of Herefordshire and 

 Scotland were being deposited, would be hardly likely 

 to contain the remains of delicate shells and the ske- 

 letons of polyps and encrinites, because, even if the 

 animals could have lived in such a sea, their hard 

 parts would be ground and pounded into ten thousand 

 atoms as soon as they were exposed to the rough 

 beating of the shingles ; while, on the other hand, the 

 clayey and sandy bottom of the more southern sea 

 might readily preserve such remains as were left by 

 animals of this kind. It would not, therefore, be sin- 

 gular that we should find a number of fossils in the 

 devonian beds very different from those in Scotland, 

 even if they were being formed at the same time; and 

 the evidence of contemporaneity offered, by comparing 

 the fossils with those of beds whose position in the se- 

 ries was known, would be sufficient to establish the 

 position of the group in question. In this way the 

 devonian strata were discovered to be of the same 



