TJie Scottish Naturalist. 209 



Thus it will be seen that, since the close of the Ice age, our 

 country has experienced several considerable geographical and 

 climatic changes, and that all these changes have been effected 

 within the lifetime of the existing fauna and flora of North-west- 

 ern Europe. 



Mrs/, there was a gradual passing away of glacial conditions, 

 accompanied and followed by a general increase of the land, 

 which united our islands among themselves and to the continent. 

 During these continental conditions our area was invaded in suc- 

 cession by the arctic-alpine and temperate faunas and floras, the 

 climate becoming eventually very genial, so that the land was 

 covered with immense forests, which reached elevations and spread 

 far north into latitudes that are now beyond the range of the 

 same trees. 



Second. This genial continental epoch eventually came to a 

 close. Enormous tracts of low-lying land became submerged ; 

 and the British area was insulated. A cold humid climate now 

 ensued ; local glaciers came down our mountain-glens, and in 

 some places reached the sea level, our coast-line being then some 

 50 feet lower than at present. The forests now disappeared from 

 wide areas, and were replaced by bogs and morasses. 



Third. By-and-bye these cold and humid conditions passed 

 away ; and the climate again assumed a drier and more genial 

 character, the sea at the same time retreating, and our shores ex- 

 tending farther seawards than they do now. This epoch was 

 marked by the drying up of bogs and morasses, and a general re- 

 newed extension of forests. The climate, although apparently not 

 so genial as that of the earlier forest-epoch, was yet more favour- 

 able to the growth of trees than the present epoch. 



Fourth. A great change of which the geologist has clear proof 

 was the renewed advance of the sea, and the formation of the 

 25-30 ft. beaches. This change was accompanied by a deteriora- 

 tion of the climate, which again became colder and wetter. Once 

 more the vertical and horizontal range of the forests was restricted ; 

 while bogs and morasses covered wide areas formerly occupied by 

 timber trees. 



Fifth. The latest change of which we have any geological 

 evidence was the final retreat of the sea to its present limits, a 

 change which seems to have been accompanied by less humid 

 climatic conditions. 



o 



