MORAINES OF RECESSION 437 
speaking of the glacial drift of the northeastern third of Illinois, 
says : 
In the portion of the state covered by the newer drift there is a succession 
of morainic ridges formed by the ice-sheet during its retreat from the Shelby- 
ville moraine. These ridges are separated by drift plains or basins from a mile 
or two up to thirty or forty miles in width. These plains usually show a 
gradual rise on their landward (west and south) borders, while on the iceward 
borders (toward the Lake Michigan basin) they are found to rise abruptly to 
a moraine. The streams which now drain this region naturally choose the 
axes of these basins for their main channels while the slopes carry the trib- 
utaries. It is the long slopes on the west and south, and the short slopes on 
the opposite side which have caused the tributaries of the streams to be 
mainly from the west and south.* 
It will be noted that Mr. Leverett speaks of the slopes of the 
plains rather than of the moraines. Each moraine, however, 
may be regarded in some sense as the projecting upward edge 
of the gently inclined plain that merges with its back slope. 
Professor Todd notes this relation in his description of the 
moraines of Dakota where he says: 
It is assumed that the reader is familiar with the generally recognized 
features of drift formations, such as the undulating topography and the series 
of drift deposits, covering an area with successive layers of till in a manner 
which might be compared to a nest of spoons of assorted sizes, the smaller 
lying inside the larger. Of these spoon-shaped deposits, the moraines form 
the outer rims.? 
It is very gratifying to be able to add to the weight of the 
foregoing opinions that of Professor Chamberlin, whose study of 
glacial problems has been close and prolonged, and whose 
experience in observation is probably wider than that of any 
other one man. It is hardly less than remarkable that his views of 
the glacial retreat should accord so closely with the requirements 
of the hypothesis here presented. 
But so far as known to the writer this manner of glacial 
t** The Water Resources of Illinois,” by FRANK LEVERETT. Extract from 17th 
Ann. Rep. U. S. Geol. Surv., 1895-6, p. 13. Also in “Pleistocene Features and 
Deposits of the Chicago Area,” Chicago Academy of Science, Bull. No. II, May 1897 
py. 
2““The Moraines of the Missouri Coteau and their Attendant Deposits,” by JAMEs 
E. Topp, Bull. U. S. Geol. Sur. No. 144, 1896, p. 11. 
