Davis.] 
344 
[January 18 , 
of the lake. Some lakes of moderate size in Wisconsin are con- 
sidered the result of glacial erosion guided by local softness of 
the rock ; 1 while they are not deeper than we may admit to be 
within the wearing power of ice, the description of them does not 
exclude the possibility of their being preglacial water valleys 
obstructed by drift. 
Other scattered examples are described in the Uinta and Hum- 
boldt Mountains of Colorado and Utah, 2 in the Pir Pinjal that 
encloses the Vale of Kashmir on the southland in the Eastern 
Himalaya. 4 
It is difficult, especially in this country, to find observations made 
and recorded with sufficient closeness to decide that a lake occu- 
pies a simple rock-basin and overflows at the lowest point of its 
rock boundary. Descriptions published more than twenty years 
ago seldom considered this point attentively and are consequently 
very inconclusive ; more recently, the occurrence of ledges in 
place in the lake outlet has been taken as sufficient evidence to 
prove a rock-basin ; but this is equally unsatisfactory unless defi- 
nite statement of the surrounding surface and slope is given as 
well. Finally, the very common existence of hybrids still further 
complicates the question. Observations on the foim of a lake’s 
shore and the neighboring country, the presence or absence of 
ledges and drift and their relative areas, the depth of the lake 
and the character of its outlet, would be of much value ; they 
might be compactly recorded and published in little sketch-maps 
Such observations are quite within reach of many who spend 
summer vacations in the woods of Maine, the Adirondacks or 
Canada, and would throw much light on a mooted question. 
B 2. Wind Erosion Basins. It has been suggested 5 that in 
regions of crystaline rocks where the progress of secular disinte- 
gration was irregular, the removal by the wind of dust arising 
1 T. C. Chamberlain, Geol. Wise., n, 1877, 137. 
2 King, Geol. Expl. 40th Par., i, 65, 470, 476. 
8 Drew, Jummoo and Kashmir, 1875. 
4 Sir R. Temple, The Lake Region of Sikkim, Geogr. Soc. Proc., in, 1881, 321-34C. 
6 Pumpelly, The Relation of Secular Rock-disintegration to Loess, Glacial Drift and 
Rock-Basins. Amer. Journ. Sci., xvii, 1879, 139. 
