viii ICE RECESSION IN NEW ENGLAND 



a theory by the number and prestige of its adherents and converts 

 instead of by careful and impartial consideration of the evidence. 

 This experience, already forgotten in the subsequent development 

 of a complete demonstration of the truth of Agassiz' theory, 

 should keep us from committing a similar mistake in our attitude 

 toward this new and surprising work of Dr. Antevs. 



Whatever advance in science comes from such studies as this 

 must be accredited in the first place to the genius of Baron 

 Gerard De Geer of Stockholm. His discovery of a simple, 

 graphic way to correlate layers of clay at one locality with the 

 layers at another locality, and thus to identify them as the 

 record of the same years, is the starting point for the new proc- 

 esses of study. In Europe the development of the new methods 

 by De Geer and his associates, Liden, Carlzon-Caldenius, 

 Sandegren, Antevs, Sauramo, and others, has already indicated 

 the possibility (a) of determining an exact time scale of late 

 glacial and post-glacial time, (b) of reconstructing the position 

 of the ice border more or less accurately during each year of its 

 withdrawal, (c) of measuring the rate of its recession, in meters 

 per year, (d) of detecting halts or zones of retarded recession 

 even where these are not registered by recessional moraines, 

 (e) of working out the complicated changes of drainage that 

 took place as ponded waters were released and modern river 

 systems inaugurated, and even (f) of computing with accuracy 

 the rate of regional uplift of the region during the departure of 

 the ice sheet. In short, De Geer and his colleagues have made 

 great progress in the working out of a detailed history of the 

 retirement of the border of the last land ice from northern 

 Europe, of the evolution of climate, and of the migrations of 

 plants, animals, and primitive man. The literature of these 

 studies is but little known in America; and the few reviews and 

 abstracts covering them suffer from lack of a first-hand knowledge 

 of unpublished studies such as that which Dr. Antevs possesses 

 and uses in this memoir to good advantage. It will be noticed 

 that he sees limitations as well as wonderful possibilities in the 

 methods inaugurated by De Geer. 



