Davis.] 
854 
[January 18, 
well. This explanation of the formation of plains is earned to 
an unwarranted extent by Belt, who considers Northern Siberia 
to mark the area of a former lake, dammed by the advance of 
Arctic ice, and applies the suggestion to many other regions as 
well. 1 
C. 3. Moraine Barrier Basins. Lakes are often found behind 
the abandoned terminal moraines of old glaciers. The normal 
terminal moraine is dropped at the foot of its halting glacier, 
stretching more or less continuously across its valley in a curved 
line, convex downward : it is often breached by the streams that 
flow from under and off of the ice, so that on the melting back 
of the glacier no lake will appear ; but again it happens that the 
moraine grows faster than the escaping water can carry it away ; 
then on the retreat of the ice, a lake will form. These lakes are 
not very durable : the entering stream, charged with sediment, 
rapidly fills the hollow ; the moraine is of loose texture and is 
readily cut down at the outlet ; and when the filling and lowering 
processes meet, the lake is converted into a flat meadow with a 
stream meandering through it, and this in turn will be gradually 
washed away till the valley is clear again. It is in this meadow 
condition that many small moraine lakes are now found; a good 
example is seen half way up Pike’s Peak, 2 and in all mountains 
that have suffered glaciation they are very common. The Twin 
Lakes in the upper valley of the Arkansas are also examples of 
the species 3 ; the list can be made as long as desired. 4 
iGeol. Soc. Journ., xxx, 1874,490: he had earlier suggested the damming of the 
St. Lawrence outlet of the Great Lakes by ice. 
2 Shaler and Davis, Glaciers, plate xix. 
3 U. S. Geol. Survey of the Territories, 1873, 47; 1874, 47. 
4 Ramsay, On the Superficial Accumulations, etc., of North Wales, Geol. Soc. Journ., 
vm, 1852, 374. 
Loch Skene and others in Scotland; Young, Geol. Soc. Journ., xx, 1864 ; A. Geikie, 
Scenery of Scotland, 1865, 81, 171, 259. 
Lac de Lourdes, Pyrenees; Martins, Soc. Geol. Bull,, xxv, 1867, 156. 
Grad, Lacs et Reservoirs des Vosges, Club Alpin Franpais, Ann., iv, 1878, 496; also 
Soc. Geol. Bull., xxvi, 1868-69, 677-686. 
On the Hohe Tatra, Carpathians; see map, Erganzungsheft 12, Peterm. Geogr. 
Mittheilungen. 
On the Pir Panjal; Drew, Jummoo and Kashmir, 202. 
In Norway; Codrington, On the probable Glacial Origin of some Norwegian Lakes, 
Geol. Soc. Journ., xvi, 1860, 345-346; Helland, id., xxxm, 1877, 170; Kjerulf, Geol. 
Norwegen, 1880, 45. 
