THE POPULAR SCIENCE MONTHLY 



paleolithic stage began toward the close of the later cold epoch 

 and extended well toward the historic period, probably overlapping 

 far upon the neolithic stage. Thus the place of paleolithic man in 

 the chronograph afforded by geology is that shown in Fig. 1. 



It should be pointed out that the human period of America 

 can not be synchronized with that of Europe, since the geologic 

 chronometer employed abroad is not sufficiently sensitive. It is 

 true that Penck * and others have recently read from the glacial 

 and associated deposits of the Alps a climatal record coinciding 

 exactly with that recognized in this country \ (save that the du- 

 ration of the episodes is less closely measured), and that Mortillet J 

 and others have inferred a definite climatal sequence from the 

 Conspectus of Quaternary History. 



is- 



^2 



li 



Formation of Lake 

 Agassiz clays and 

 Champlaiu depos- 

 its. Terminal mo- 

 raines and third 

 drift-sheet. 



f Relatively short 

 a-glacial interval. 

 Erosion of river- 

 valleys. 



Loess passing into 

 second drift-sheet 

 in central U. S. 

 Upper lake-beds 

 in the Great Ba- 

 sin. Moraine-bor- 

 dered drift in east- 

 ern U. S. 

 f Long a-glacial in- 

 I terval. Formation 

 I of medial gravels 

 J in Great Basin and 

 forest bed in Mis- 

 sissippi Valley. 

 Ercsion in eastern 

 U. S. 



Lower lake-beds in 

 Great B'sin, "Gum- 

 bo" passing into 

 first drift-sheet in 

 Mississippi Valley, 

 Columbia forma- 

 tion in eastern U.S. 



The German Alps. 



Post- 

 glacial 

 period. 



Last 

 glacial 

 period. 



Last 

 inter- 

 glacial 

 period. 



Erosion of valleys ; 

 filling up of gla- 

 cial lakes. 

 Erosion in the cen- 

 tral part, moraine 

 building at the pe- 

 riphery, and sedi- 

 mentation by ice- 

 fed streams with- 

 out the glaciated 

 districts. 

 Erosion of valleys ; 

 I filling up of gla- 

 l cial lakes ; torma- 

 I tion of Innsbruck 

 [^ coal, etc. 



Northern France. 



Middle "| 



(sec- I Moraine - building ; 



ond) j- sedimentation by 

 glacial I glacial streams, 

 period. J 



f Erosion of valleys ; 

 filling up of gla- 

 First I cial lakes ; forma- 

 inter- J tion of old deltas 

 glacial I and breccias, river 

 period. alluvium, and lig- 

 nites with associ- 

 [ ated deposits. 

 First i Erosion and depo- 

 glacial •] sition by ice and 

 period. ( glacial streams. 





rColdanddry. For- 

 ' mation of red al- 

 luvium ; atmos- 

 pheric deposits. 



Milder tempera- 

 ture ; very short 

 relatively. Con- 

 tinuation of ter- 

 race formation ; 

 retreat of glaciers 

 f Cold and wet. For- 

 I mation of ter- 

 I races, great ex- 

 tension of gla- 

 ciers, clearing out 

 of valleys, and ac- 

 cumulat'n of soil. 



Warm and wet. Su- 

 perior loam, high 

 Ic^el alluvium, 

 filling up of val- 

 leys, and remo- 

 val of soil. 



(Not represented.) 



* " Die Vergletscherung der dcutschen Alpen," 1882, Tabelle IL 



■)• "American Journal of Science," third series, xxxv, 1888, pp. 462-466. 



X "La Prehistorique Antiquit6 de THomme," 1885, p. 131. 



