Erratic Blocks of Northern Europe. 143 



striae are now below the waters. These results, although 

 opposed, are not, as they may at first appear, contradictory ; 

 and it is here that the observation of shells completes the 

 study of erratic phenomena, properly so called, by shewing 

 us the chronological order of these events. In fact, the bar- 

 nacles of Uddevalla, and the serpulas of Christiania, which 

 are found, the former at the height of 200, and the latfcer of 

 170 feet above the sea, prove irresistibly that the coast has 

 sunk in those places ; the fact that these animals are ad- 

 hering to striated rocks, shews not less certainly that the 

 rocks were dry before these animals were living there ; 

 whence I read this double conclusion, 1^/, that the graving of 

 tlie rocks was anterior to the epoch of the barnacles and ser- 

 pulas ; and, 2d, that, to receive these animals, the coasts of 

 Uddevalla and Christiania must have sunk as far, at least, as 

 would be equivalent to the actual height of these fossils. 



But the barnacles and serpulas are not the only proofs of 

 this subsidence. At a much greater height we find shells, 

 over these polished and striated rocks, imbedded in the dilu- 

 vium ; and as the species are in general indigenous, and pro- 

 bably contemporaneous with the serpulas and barnacles, it 

 follows, of course, that the submergence must have been con- 

 siderable, and equal, at least, to the site of the highest shells 

 of the diluvium (800 feet). This submergence must, conse- 

 quently, have taken place between the epoch of the furrowing 

 and the stratification of the diluvium. At that time, the gla- 

 ciers having quitted the plain to retire to the interior moun- 

 tains, the waters of the sea invaded the low country of Scan- 

 dinavia, surrounding the solid masonry of the Scandinavian 

 mountains with an ocean to which we shall be able to fix 

 some approximate limit when we are acquainted with the 

 boundaries of the region of diluvial shells. In passing, I 

 would remark, that the analogy of the erratic blocks of Fin- 

 land with those of Scandinavia, allows us to believe that at 

 that time the Gulf of Bothnia was not separated from the 

 Arctic Sea. 



We have no means of determining the length of time which 

 elapsed between the retiring of the glaciers, and that sub- 

 siding of the land which led to the invasion of the sea. How- 

 ever the perfect preservation of the polishing beneath the 



