1882.] 31 [Davis. 



(one and eight-tenths) the material supposed to be excavated in 

 making the former ; this excess is considered due to addition of fragments 

 distinctly referable to the region south of Lake Wenern. But it should 

 be noted that the hilly surface of Seeland 1 points to its being precisely one 

 of the regions of concentrated deposit — an old halting place of the ice — 

 and consequently it should not be directly compared with an equal area 

 farther north. Helland farther estimates that the area of the Scandinavian 

 Peninsula from which the drift came, is to the area of North Germany and 

 North Western Russia on which it was deposited, as two is to five ; and 

 that the average depth of drift on the latter, estimated in conference with 

 several geologists familiar with the region, is one hundred and fifty German 

 feet: allowing one third of this to be of local derivation, the proportion of 

 areas requires the average thickness of the drift carried from Scandinavia 

 to be two hundred and fifty feet. This is certainly an impressive showing. 

 I should like to find a confirmation or criticism of it by one less pro- 

 nounced than its author in favor of great glacial erosion. It may be 

 noted that even two hundred and fifty feet of detritus might be largely sup- 

 plied by preglacial disintegration from so old a land surface as Scandinavia 

 and also that even this thickness would still negative the idea that the val- 

 leys and fjords were of glacial origin. 



* A. Penck gives twenty meters for the average thickness of the ground 

 moraine of the old Isar glacier in Southern Bavaria, and this corresponds 

 to an erosion of thirteen meters in the mountains from which the ice moved. 

 Including all the glaciers that advanced from North Tyrol on to the high 

 southern plain of Bavaria, and taking the waterworn pebbles and sands that 

 were carried by glacial streams with the ground moraine, the average total 

 thickness is sixty meters, and this restored to its origin would raise the gen- 

 eral mountain surface by thirty-six meters. (Vergletscherung der deutschen 

 Alpen, Leipzig, 1882, 201, 330, 387). 



N. S. Shaler (Illustrations of the Earth's Surface ; Glaciers, 58), esti- 

 mates the total amount of drift on New England and in its neighboring 

 terminal moraines at 750 cubic miles, or more than the mass of the White 

 Mountains. Supposing this to be derived from an area of sixty thousand 

 square miles, it would have had an average thickness, if evenly distributed, 

 of about sixty-five feet. This is not far from the possibilities of preglacial 

 soils and valley alluvium ; and although the total mass of the drift is verv 

 great, the fact that it was derived from a broad area shows that no exces- 

 sive local erosion took place. 



A careful measure of the drift in three of the Northern Central States 2 

 has lately been made by E. W. Claypole. (Evidence from the Drift of Ohio, 



1 Forchhammer, Pogg. Ann. lviii, 1843, 628. 



2 According to the divisions proposed by Gannett, which should certainly be adopted 

 in our new Geographies. See Census Bulletin, No. 277, 1881. 



