422 REPORT OF NATIONAL MUSEUM, 1904. 



The drift phenomena of the region studied by Foster and Whit 

 Desor on the ney were described by E. Desor, who divided the 



deposits into four classes, as follows, beginning 

 with the lowermost: 



* 1. A layer of coarse, pebbly loam called "coarse drift." 



2. Clay resting either on the coarse drift or directly on the rock. 



3. A deposit of sand, gravel, and pebbles, irregularly stratified, resting upon the 

 clay or the bed rock. 



4.. Isolated bowlders scattered over the whole region. 



While disclaiming any intention of giving a general theory for the 

 causes and origin of the drift, he argued that the phenomena he 

 described indicated neither paroxysmal agencies nor the operation of 

 any single cause, however long continued. "They disclose a long 

 series of events which have resulted from causes highly diversified, 

 and as yet imperfectly known. Three periods are recognized in the 

 history of the drift of the Lake Superior region: (1) 'The period of 

 the grooving and polishing of the rocks, 1 which ' must be considered 

 as the dawning of the drift epoch;' (2) a period of comparative qui- 

 escence, extending over a long period of time and during which the 

 stratum of red clay was deposited. This is the second era of the drift. 

 (3) The overlying stratum of sand and gravel presumably formed by 

 water, but at higher levels than the clay and indicating a still further 

 depression of the land. This period characterized by intervals of agi- 

 tation and repose. He considered that earthquake waves, according 

 to H. I). Rogers's ingenious theory, might be responsible in part for 

 these. " 



The transportation of the bowlders, he thought, took place at the 

 close of the drift epoch. 



In another article in the American Journal of Science for the same 

 year (1852), concerning the post-Pliocene of the Southern States and 

 its relation to the Laurentian of the North and the deposits of the 

 Mississippi Valley, Desor attempted to account for the large bowlders 

 in the drift of Long Island by means of ice rafts. The bowlders in 

 the post-Pliocene of the Southern States were doubtfully referred to 

 water action only. 



Desor, according to Marcou, was a German, who had come to Amer- 

 ica as private secretary to Agassiz, and whatever views he may have 

 had on glaciation or other scientific subjects maybe regarded as mainly 

 absorbed rather than learned from observation. Through becoming 

 over-presumptuous he had a falling out with his master, which resulted 

 in his discharge in 1848 and return to Germany in 1852, passing thus 

 beyond the limits of our field of study. 



J. D. Dana, as already noted, served as geologist in the United 

 States exploring expedition under Captain Wilkes, during the years 

 L838-42. The results of his observations during this time are embod- 



