748 



SCIENCE. 



[N. S. Vol. XVI. No. 410. 



bulletin of the New York Agricultural Ex- 

 periment Station. H. J. Eustace. 

 Geneva, N. Y., 

 October 24, 1902. 



CVBBENT NOTES ON PHYSIOOBAPET. 

 THE MISSISSIPPI IN SOUTHEASTERN MISSOUHI. 



Theee is a narrow belt of lowland in south- 

 eastern Missouri that is separated from the 

 broad lowland flood plain of the Mississippi 

 by a low upland known as Crowley ridge. 

 Marbut gives an interesting explanation of 

 these features (' The Evolution of the North- 

 ern Part of the Lowlands of Southeastern 

 Missouri,' Univ. of Missouri Studies, I., 1902, 

 No. 3, viii + 63 p., 5 pL, 2 maps). The two 

 lowlands have been eroded by the Mississippi 

 and the Ohio rivers, whose confluence origin- 

 ally lay south of Crowley ridge. A series of 

 changes, well worked out by the author, re- 

 sulted in two successive captures of the Missis- 

 sippi, whose flood plain was at a higher level, 

 by the Ohio, whose flood plain was at a lower 

 level. The first capture was at the head of 

 Crowley ridge ; and here the river ran long 

 enough to open a flood plain thirty miles wide. 

 The second capture was fifteen miles farther 

 northeast, at the head of a smaller upland 

 called Benton ridge, where the new twenty- 

 mile course of the great river has been so 

 lately assumed that it is still a narrow gorge 

 without bordering flood plain. Crowley and 

 Benton ridges are, therefore, in a certain 

 sense examples of that peculiar class of hills 

 which results from the isolation of the term- 

 inal part of a ridge between two rivers when 

 a new point of confluence is developed, up- 

 stream from the former point; the notable 

 feature of this case being the unusual length 

 of the first (Crowley) isolated portion of the 

 ridge. This origin of the ridge had been sug- 

 gested in general terms by earlier writers ; but 

 to Marbut belongs the credit of demonstrating 

 the changes involved and of explaining closely 

 the processes by which they were brought 

 about. 



LAKES IN THE GLAHNER ALPS. 



The origin of the small lakes in the higher 

 valleys of the Glarner Alps, southeast of 

 Zurich, is discussed in a doctorate thesis of the 



University of Basel by S. Blumer (' Zur Ent- 

 stehung der Glarnerischen Alpenseen,' Eclog. 

 geol. helvet., VII., 1902, 203-244, 4 pi.). He 

 concludes that the lake basins are all closely 

 associated with the former glaciation of their 

 valleys. Most of the basins are described as 

 relatively insignificant depressions due to 

 glacial erosion in an old valley floor ; but some 

 of them are enclosed, in part at least, by tor- 

 rential fans, -and others are associated with 

 underground discharge in limestonesT 



This essay shares with many others a plan 

 of treatment that seems, in view of recent 

 studies of glacial erosion, to give a too limited 

 consideration to the problem in hand. It is 

 tacitly implied that the rock barriers next 

 below the basins have not suffered any signifi- 

 cant amount of erosion; and hence that prac- 

 tically the whole measure of glacial erosion is 

 seen in the depth of the basins above the 

 barriers. Many recent studies indicate, on the 

 other hand, that both basins and barriers in 

 glaciated valley floors have suffered severe 

 erosion, and that the excess of erosion in the 

 basin over that on the barrier is a relatively 

 small fraction of the total erosion by which 

 the valley trough — the glacial channel — as a 

 whole was deepened. The origin of lake basins 

 in glaciated districts therefore calls for a gen- 

 eral study of the entire valley in whose floor 

 the lake occupies only a ' relatively insignifi- 

 cant depression ' ; jvist as the origin of a pool 

 in a dry river bed involves the explanation of 

 the whole river channel, and not merely of the 

 pool alone. It may also be noted that the tor- 

 rential fans by which so many of the Swiss 

 valleys are obstructed, in some cases to the 

 point of barring lakes, are best explained as 

 indirect consequences of glacial erosion; the 

 stream in the over-deepened main valley being 

 unable to sweep away the abundant detritus 

 washed in by the over-steepened side streams 

 that leap down from their hanging valleys. In 

 a word, the study of Alpine lakes demands a 

 more general treatment than it is given in 

 Blumer's essay. 



THE LAKES OF WALES. 



The deficiency just pointed out is largely 

 remedied in 'A Bathymetrical and Geological 



