456 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 30 



variations arc no longer unknown quantities; they are plainly legible 

 in the varves themselves. In a year with a warm summer the coarse 

 portion of (he varve will be thick; in a colder year the varves may 

 shrink to small lamellae. Exceptionally rainy seasons and periods 

 of excessive heat and drought will undoubtedly modify the deposi- 

 tions in lakes at the ice front. But such irregularities can always 

 be distinguished from the seasonal varves if the latter are studied 

 with due care over large areas. 



De Geer's method has also been applied to varved clays in North 

 America during the last decade. Antevs started this work in the 

 Connecticut Valley. Varves were counted from Hartford, Conn., 

 to northern Vermont, over a distance of 185 miles. Later, a number 

 of varved clay deposits were studied in Canada, in Wisconsin and 

 Minnesota, and recently by Chester A. Eeeds in New Jersey and in 

 the Hudson Valley, New York. 



The researches have even been extended to Argentina in the 

 Southern Hemisphere and to the Himalaya region. It has not been 

 possible in these cases to construct a continuous time scale as in 

 Scandinavia. But the method itself has been firmly established and 

 has stood the test by many independent Avorkers in widely separated 

 areas. 



EXTENSION OF THE CHRONOLOGY BACKWARDS 



The duration of late glacial and postglacial time in Scandinavia 

 has been firmly established by De Geer and his colleagues. In round 

 numbers, 13,500 years have passed since central Scania was freed 

 from ice. How can this fact be used toward solving the problem of 

 the age of the human race? This age is certainly higher than the 

 above figure. In the first place, it must be taken into account that 

 the ice border halted a considerable time before it melted away, 

 forming moraines — that is to say, long stretched hills — composed of 

 the detritus brought by the ice. Recently the duration of this stop- 

 page, just before its final recession, has been determined by studying 

 varved clays laid down by the melting waters of the ice in lakes of 

 southwestern Scania and in the Danish islands Sjelland and Fyen. 

 (See De Geer, citation 4 above.) This halt of the ice lasted almost 

 2,000 years, which, therefore, must be added to the above figure 

 13,500. 



Furthermore, it is well known that the ice before this time covered 

 the northernmost part of Germany, halting there again for a con- 

 siderable time, as is seen from the formation of the very extensive 

 elevations, the moraines of the Baltic Ridge, in which lakes and lake- 

 lets are abundantly developed, as in the moraines of Wisconsin and 

 Minnesota. The duration of this stoppage and the time required for 

 the retreat from northern Germany to southern Scania have not yet 



