1882 .] 
849 
[Davis. 
the warped valley basin from south and north about oppo- 
site each other: Interlaken stands on the beautiful alluvial plain 
thus formed. 1 Similar lateral deltas separate Lakes Sils and Sil- 
vaplana in the Engadin, 2 Lago di Mezzola from the head of Como, 
and Derwent Water and Bassenth waite, 3 Crummock Water and 
Buttermeer in the lake district of England. 4 Returning to Switz- 
erland, the Wallen See is cut off from Lake Zurich partly by the 
alluvial deposit of the Linth, as well as by orographic change ; and 
Lake Bienne standing in the upper part of an old river valley, is left 
emp>ty, while below the entrance of the Aar, the channel is silted 
up as far as Olten. The alluvial deposits in the flat valley of Cali- 
fornia are raised a little higher opposite the discharge of King’s 
River from the Sierra, and in the faint depression south of this 
gentle delta stand Tulare lake and the swampy flats south to Kern : 
the first is only about forty feet deep, although 680 square miles 
in maximum area. 5 
Lake Pepin, an enlargement of the Mississippi, is caused by the 
excess of deposit brought by the Chippewa ; the lake is shallow 
from overflowing on to an open valley. The Wisconsin and Illi- 
nois rivers attempt the same kind of obstruction, but with less 
success ; it is only at low water in the dry season that the Missis- 
sippi assumes the appearance of a lake above their points of con- 
fluence. 6 
A subspecies may include certain lakes in side valleys, held 
back by an excess of detritus brought by the main stream and 
deposited so as to raise its bed in front of the lateral branches. 
This seems to be the origin of Lakes Bistineau, Fentry and Cross, 
draining into the Arkansas River in northwestern Louisiana; 
they are shallow, from overflowing flat bottom lands, the first 
named being only fifteen or twenty feet deep, although some 
thirty miles long. 7 In the same way, the back water by the 
mouth of the Minnesota is held up by the Mississippi. 
1 J. de Charpentier, Essai sur les Glaciers, 1841, 343, note. 
2 Heim, Die Seen des Oberengadin, Schw. Alpenclub, Jahrb., xv, 1880. 
3 Playfair, Illustrations of the Huttonian Theory*, 1802, 359. 
4 Ward, Geol. Soc.'Journ., xxx, 1874, 96 and map. See also Kinahan, Valleys, 116 : 
such a double lake is known in Ireland as a “ lough-a-voul ” (lake of the two spots). 
5 Whitney, Auriferous Gravels of the Sierra Nevada, 2. 
6 Warren, Amer. Journ. Sci., xvi, 1878,420. 
7 Lyell, Principles of Geology, i, 45 0. 
