QUATERNARY DEPOSITS OF BRITISH ISLES — BROOKS. 301 



Second interglacial. — Formation of Archangel series in lower 

 course of northern Dwina. Finland free of ice. This interglacial 

 was marked by a subsidence in Finland. 



Third glaciation. — Reelevation of Finland. This glaciation was 

 limited to a relatively small area in Finland and northwest Russia. 



The limits of the second and third glaciations have not yet been 

 traced in detail, and no formations similar to those of the Baltic 

 interstadial have yet been discovered. 



5. SCANDINAVIA AND THE BALTIC. 



The centers of ice accumulation in Scandinavia were necessarily 

 areas of erosion, where the thick ice swept the rock surface clear 

 of all superficial detritus, and transported it often to very consider- 

 able distances. Consequently, every glaciation in these regions would 

 tend to destroy the evidences of the preceding one, so that it becomes 

 hard to tell whether tliere have been more than one glaciation, i. e., 

 whether the ice retreats and interglacial periods of the peripheral 

 regions extended into the center of ice distribution, leaving the whole 

 country clear of ice, or only to its margin. 



Nevertheless, there are a few traces of such deglaciation which, 

 considering their necessary rarity, entitles us to assume the practically 

 complete disappearance of the ice. These were discussed by A. G. 

 Hogbom in 1913 (50) . He refuses to accept the thick sand beds, un- 

 fossiliferous or with only arctic remains, in Schonen as interglacial, 

 since they show no evidence of any rank higher than interstadial. 

 On the other hand, the fossiliferous deposits with a boreal fauna and 

 flora overlain by glacial deposits described by H. Munthe (51) at 

 Hernosand and Erikson (52) at BoHniis, both in north Sweden, he 

 considers to be very probably truly interglacial, as well as the fos- 

 siliferous beds intercalated in thick moraine deposits in Jaederen. As 

 further evidence for at least one interglacial period he mentions the 

 finding of teeth of mammoth in Schonen, Finland, and central Nor- 

 way and remains of musk ox at Gothenburg. 



The deposit at Hernosand appears to be the most important of 

 these ; it was described by H. Munthe in 1899, 1904, and 1909, and by 

 A. G. Hogbom in 1910. The section is as follows: 



3. Typical feebly calcareous moraine clay; 3 to 5 meters. 



2. Brown gyttja and sandy gyttja, rich in fossil Quaternary fresh-water 



and land organisms; 0.7 to 3 meters. 

 1. Glacial sand, gravel, and blocks (partly ice scratched) ; 2.8 meters. 



The Gyttja is partly a somewhat impure diatom and Cladocera 

 formation, partly more or less mixed with fine sand ; it usually shows 

 a breccia structure. The plants include Betula odorata^ B. nana, 

 Pinus silvestris, and Picea eotcelsa. It appears to have been de- 



