472 PLEISTOCENE OF INDIANA AND MICHIGAN. 



of the land at the north caused the discharge of the upper lakes to shift from northerly to 

 more southerly passes, thus implying a reestablishment of the full volume of discharge south- 

 ward through St. Clair and Detroit rivers. 



Gilbert does not go into the details of the history of the connecting rivers in his paper, 

 but the abandonment and reoccupation which he describes were important factors in the 

 development of these great river beds. In a later paper 1 he discusses the Great Lakes history 

 in much the same way, without going into details relative tc the other connecting rivers. In 

 an article on recent earth movements in the Great Lakes region, 2 he recognizes the "drowned" 

 character of the lower stream courses around Lakes Ontario and Erie, the southern half of 

 Lake Michigan, and the south side of Lake Superior and attributes it to recent tilting of the 

 land. The connecting rivers seem obviously included, but are not particularly mentioned. 



In 1903 Cole 3 made a special study, under the direction of the Michigan State Geological 

 Survey, of the delta of St. Clair River. 



In his report on the geology of Monroe County, Mich., Sherzer discusses very briefly some 

 rather exceptional till ridges in Monguagon and Brownstown townships, in Wayne County. 4 

 These ridges are separated by very well denned and persistent troughs, but Sherzer gives the 

 ridges first importance, regarding them as parts of a moraine which he calls the Detroit moraine, 

 and assigning no unusual quality or origin to the troughs. He gives a good description of the 

 recent drowning of the shores of Lake Erie along the border of Monroe County, but does not 

 discuss the distributaries of the Trenton district, which lie outside of that county. 



In two papers published early in 1895 the writer 5 attempted to give the main outlines 

 of the Great Lake history on the hypothesis of marine invasion of the upper three lakes and 

 marine origin for some of the higher beaches of that region. Glacial lakes retained by ice 

 dams were supposed to account for nearly all the beaches in the southern part of the Great 

 Lakes region, but not in the northern. The Trent Valley outlet at Kirkfield, Ontario, had not 

 then been visited by the writer, and Spencer's then recent rejection of it as a thing of impor- 

 tance was accepted. The name Lake Algonquin was applied to two different lake stages, the 

 First Lake Algonquin and the Second Lake Algonquin. An eastward uplift separate from 

 and later than the general northward uplift was postulated. On account of the incompleteness 

 of the data then in hand and on account of the confusion introduced by erroneous postulates 

 and interpretations, these two papers were both seen within a year to have been premature 

 and except for a few passages are now worse than useless. Both include statements and 

 interpretations bearing on the development of St. Clair and Detroit rivers and on Lake St. 

 Clair and on the growth of the St. Clair delta which are almost all wrong. 



The larger errors of these two papers were set right by investigation on the north shore 

 of Lake Superior and in the Mattawa and Ottawa valleys in the fall of the year of publication 

 (1895), and the corrected results were published in brief form the next spring. 6 After further 

 studies in 1897 a more detailed though brief account of the features near Detroit was published. 7 



ST. CLAIR-DETROIT VALLEY. 



The drainage system of the broad flat valley which lies between the south end of Lake 

 Huron and the west end of Lake Erie must have had a long and complex history in preglacial 

 times and in the times of the earlier ice sheets and interglacial intervals. It is not the purpose, 

 however, to discuss this phase of its history here, but to present an account of the way in which 

 the modern rivers became established after the recession of the last ice sheet. The outlet chan- 

 nels and connecting rivers which are now abandoned have already been described. 



i Niagara Falls and their history: Nat. Geog. Mon. No. 7,' vol. 1, 1895, pp. 227, 229. 



2 Recent earth movements in the Great Lakes region: Eighteenth Ann. Eept. U. S. Geol. Survey, pt. 2, 1897, pp. 601-647, especially pp. 605-606. 

 Also more briefly in Nat. Geog. Mag., vol. 8, 1897, pp. 233-247. 



s Cole, L. J., The delta of the St. Clair River: Geol. Survey Michigan, vol. 9, pt. 1, 1903, pp. 1-25. 



* Sherzer, W. H., Geological report on Monroe County Mich.: Michigan Geol. Survey, vol, 7, pt. 1, 1900, p. 135. 



5 The second Lake Algonquin: Am. Geologist, vol. 15, 1S95, pp. 100-120, 162-179; Niagara aud the Great Lakes: Am. Jour. Sci., 3d ser., vol. 

 49, 1895, pp. 249-270. 



e Preliminary notes on studies of the Great Lakes made in 1895: Am. Geologist, vol. 17, 1896, pp. 253-257. 



' Some features of the recent geology around Detroit (abstract): Proc. Am. Assoc. Adv. Sci., 1897, pp. 201-202. 



