76 MR SMITH ON THE CHANGES 



in times which, geologically speaking, are extremely recent ; 

 such a change as would send the gulf stream to the south 

 of the line, or into the Pacific, would necessarily reduce the 

 temperature of our seas, and account for the Arctic charac- 

 ter of the shells. 



The evidences of depression furnished by the terrestrial 

 deposits, which have been called submarine forests, are not 

 less conclusive than are those of elevation derived from the 

 marine beds. They occur on the west coast, in the Western 

 Islands, the Orkneys, and in several points of the east coast 

 of Scotland. The most extensive is that of the basin of 

 the Tay, which has been described by Dr Fleming. It 

 has been observed in detached portions for about ten miles 

 on the south side of that river, and also on the opposite 

 shore, and extends through the whole of Strathearn.-j- It 

 may be described as a bed of peat containing stumps of 

 trees in the attitude of growth, resting upon beds, apparent- 

 ly of marine origin, and covered by others containing ma- 

 rine shells. There can be no doubt, therefore, as to its re- 

 lative age. In the statistical account of the parish of Long- 

 forgan,J we have the following interesting description of 

 it. " By an examination lately taken at the Braes of 

 Monorgan and Folgavie, where the river Tay has made 

 its greatest encroachments, and where the banks are from 

 19 to 20 feet perpendicular height, the following strata can 

 be distinctly traced. 1st, A brownish clay mixed with sand 

 and vegetable earth, about 1| foot deep, forming the pre- 

 sent prolific upper surface. 2d, About 4 feet deep of a 

 brownish free clay, with a proportion of sand, but no vege- 

 table matter. The only difference between these two is 

 probably owing to cultivation, manure, sun, and air. 3d, 



* Transactions of the Royal Soc. Edin. vol. ix. p. 419. 

 tNew Stat. Acct. No. x. p. 60. J Vol. xix. p. 556. 



