1898.] WILLIAMS — ON KAXSAX DRIFT IX PENNSYLVANIA. 85 



miles in width, while the western averages but six. This is in 

 accordance with the deductions of the late Prof. James D. Dana, 

 in the last paper he wrote on glaciation, in attempting to account 

 for the wide difference between the eastern and western deposits. 

 It is well known that Mr. Upham began his work in the east and 

 held to the theory of a single glacial epoch. After work in the 

 west he accepted that of two or more periods. On his return to 

 the east he returned to his first opinion. This is an epitome of the 

 wide difference in appearance between the few strong moraines of 

 the east and the multiplicity of the deposits of the west, and Prof. 

 Dana theorized that such difference must have been caused by the 

 abundant precipitation of the east and the scanty precipitation of 

 the west, so that the deficit of dry seasons would bear a smaller 

 proportion to the total precipitation in the east than in the west, and 

 the strength and persistence of the ice at certain latitudes in the 

 east would be balanced by the many fluctuations of the west. The 

 strength thus predicted for the eastern glacier is shown by the wider 

 margin found and by the variation in the position of the apex. 

 While the western Kansan ice retreated to the position taken by the 

 Wisconsin margin, the relaxation of the pressure was accompanied 

 by an advance of the eastern ice across the region of the apex. 



The second claim for a double origin substantiates the theory, as 

 there was found in the summer of 1897, at East Warren, Pa., forty 

 feet below the original surface and 100 feet above the water of the 

 Allegheny river, a rolled piece of native copper as long and thick 

 as the finger, in a lenticule of dense till which resisted the pick. 

 The matrix of clay had preserved the copper from oxidation to such 

 an extent that its surface was still smooth, and with it were found 

 fresh rolled and glaciated crystalline pebbles and local angular 

 elastics. This lenticule was about 120 feet above the rock surface, 

 as shown by a neighboring well section, and the original thickness 

 of glacial deposit was thus 160 feet. This find shows that the 

 western ice traversed the region of the great lakes in a southeastern 

 direction and proves that we had a meeting of two ice sheets near 

 Salamanca, N. Y. The variations in strength and the varying 

 number of moraines of the eastern and western glaciers are thus 

 satisfactorily settled in a simple manner. It remains to say that the 

 writer was unaware at the time he first made the claim for two ori- 

 gins that Prof. Wright had surmised the same (/<:<? Age, p. 443) 

 from the symmetry of the moraine delimited by Mr. Lewis and 



