90 ICE RECESSION IN NEW ENGLAND 



informed by Mr. R. W. Sayles that in varve clay taken by him 

 at locality 78, about 10 feet above the till, Dr. E. C. Jeffrey 

 found microscopic fragments of coniferous wood. 



In Sweden the rate of the ice retreat from the south coast of 

 Blekinge (56°N.) to Ragunda (63°N.) in Norrland (450 miles, or 

 720 km., in 4,000 years) averaged about 600 feet (180 m.) a year 

 (De Geer, 1912, 1915). In the southern part, from Blekinge to 

 the Fenno-Scandian moraines (150 miles, or 240 km., in 2,000 

 years), the annual recession amounted to 400 feet (120 m.), and 

 in the northern part, from the moraines up to Ragunda (280 

 miles, or 450 km., in 1,500 years) to 1,000 feet (300 m.). The 

 morainic belt represents two halts and slow intervening recession 

 for together nearly 700 years (Sauramo, 19 18, p. 23). 



In New England, between Hartford, Conn., and St. Johnsbury, 

 Vt. (185 miles, or 298 km., in 4,100 years), a zone lying closer to 

 the periphery of the last ice sheet than does Sweden, the annual 

 recession averaged about 240 feet (75 m.), i. e. less than one-half 

 of that in Sweden. Assuming that during the ice retreat the 

 supply of ice was the same in Sweden and New England and that 

 the rate of recession reflects the temperature to the same extent 

 in both regions, it must have been considerably warmer in 

 Sweden when the ice disappeared there. Accordingly, the 

 knowledge of the late glacial climate in Sweden cannot be directly 

 applied to New England. As far as this is based on the immigra- 

 tion of the flora, it should be noted that this migration occurred on 

 a narrow front across the Danish islands, which from time to time 

 connected Sweden with the continent (Antevs, 1922), while the 

 migration northward in New England occurred on abroad front. 



In southern Sweden the land uncovered from the vanishing 

 ice was first taken possession of by an arctic to subartic flora with 

 Dryas octopetala as its most typical constituent. Even before 

 the disappearance of this flora, birch (Betula odorata and Betula 

 verrucosa) and pine {Pinus silvestris) were more or less abun- 

 dant (von Post, 1916). The temperature may have corresponded 

 to that now prevailing in northern Scandinavia (Andersson and 

 Birger, 1912, p. 130). Alder {Alnus glutinosa)> elm (Ulmus 



