Pleistocene Geology of Moravia Quadrangle 431 
800-1 100 
11-1200 
12-1300 
13-1500 
i 
15-1700 
00 
§ 
S. 14° E. 
S. 26° E. 
S. 51° E. 
S. 66° E. 
1 
S.75°E. 
S. 57° E. 
S. 37° E. 
S. 44 ° E. 
S.5o°E. 
S. 56° E. 
S. 51° E. 
S.45"E. 
S. 46°E. 
S.48°E. 
S. 3 i°E. 
S. 49° E. 
S. 55°E. 
S. 72°E. 1 
S.73°E. 1 
1 
S. 6i°E. 
1 S. 7 i°E. 
S. 76°E. 
S. 45°W 
Ice-Front Channels. 
The several halts of a retreating ice-sheet naturally develop 
waterways not normal to ordinary conditions of rainfall. Often 
these waterways are narrow, occupying a slight depression some- 
times incised in rock; more often, however, they are not cut 
entirely through the previously deposited drift. Again, they are 
broad channels indicating a wide shallow stream bearing drain- 
age away from the melting ice; in this case an unusual quantity 
of bowlders, large and small, generally characterize the former 
water course. These bowlders may represent the unremoved 
heavier portions of the former drift deposits, as well as the debris 
melted from stranded ice-blocks being floated off by the waters 
flowing from the front of the glacier. 
The two types of ice-front channels may be discriminated: 
(i) Topographic, or drainage ways usually following the sags 
between or leading into the valleys of the locality; (2) Torrential, 
or channels cut generally in previously deposited drift, and hav- 
ing locations possible only when an abnormal quantity of water 
is turned loose through an area that in post-glacial times has 
never carried any considerable drainage. The former type one 
might locate with some degree of accuracy on a topographic map, 
knowing only the general positions of bands of thickened drift. 
The torrential type, however, can scarcely be hypothecated on 
any normal premises. Ice-front channels of this type are found 
often in unexpected places, particularly where the ice has melted 
slowly and the drift in consequence has become very thick. 
Topographic Type, (i) About a mile southwest of West Dryden 
is an area now covered by extensive swamps. This flat region leads 
away from northwestward falling contours to contours descend- 
