448 PLEISTOCENE OF INDIANA AND MICHIGAN. 



The "correlation of a particular beach in the Lake Superior and Lake Michigan basins with 

 the outlet at North Bay was made in 1893 by the writer on an excursion in company with 

 Dr. F. S. Pierce, of Philadelphia, and was published in 1894. 1 Since that time the beach has 

 been studied by several students of the lake history who have worked in the upper lake region, 

 and it has been mapped in considerable detail on all shores except those north and east of Lake 

 Superior, north of Lake Huron, and north and east of Georgian Bay. 



OUTLET. 



The outlet of the Nipissing Great Lakes was at North Bay, Ontario, on the northeast 

 shore of the modern Lake Nipissing. Later, differential uplift raised North Bay and gradually 

 drove the waters back to Port Huron, inaugurating a transitional two-outlet stage which 

 ended with the closing of the North Bay outlet and the transfer of the entire discharge to Port 

 Huron, thus terminating the existence of the Nipissing Great Lakes. 



The North Bay outlet river, or " Nipissing-Mattawa River," 2 after passing a swampy col, 

 amid glaciated bosses of crystalline rock, chiefly gneiss, passed down Mattawa River to 

 Mattawa, where it joined Ottawa River and followed it, at first to glacial lakes and later to 

 the sea, which occupied the St. Lawrence and Ottawa valleys at that time. 



Mattawa River is composed mainly of a chain of lakes connected by short, rapid streams. 

 Some of the lakes are long, narrow, and deep, lying in canyon-like valleys 200 to 300 feet wide, 

 with water 100 to 300 feet deep, bordered by precipitous walls 100 feet or more high. 3 



The Nipissing beach is strongly marked along the north side of the col a mile north of the 

 Canadian Pacific Railway station in North Bay 4 but is poorly developed along the south side, 

 which was an archipelago of crystalline islands largely bare. The col swamp extends eastward to 

 the head of Trout Lake, beyond which the outlet river leads through Turtle Lake, descends 

 rapidly northward to the head of Tolon Lake, leaves the latter by a cascade of 30 or 40 feet, 

 and passes through several lakes below. The lake beds show no clear evidence of the outlet 

 river, but some of the intervening stretches record the scour of a great river. In some places 

 the cross section of the scoured bed and the indicated velocity of the current show the river 

 to have had about the same volume as St. Clair River of to-day; and this would be expected if 

 this outlet carried the discharge of the same lakes after the ice sheet had ceased to contribute 

 to them. The writer made a canoe trip down Mattawa River from North Bay to its junction 

 with the Ottawa hi 1896 and later published an account of some of the evidences of the presence 

 of the outlet river. 5 



Though the erosion in the outlet channel is too slight to signify by itself that the river 

 endured for a great length of time, other features indicate that its life was by no means short. 

 It is to be remembered that its waters were drawn from clear lakes, that they had passed through 

 the long channel of French River and through the basin of the modern Lake Nipissing before 

 they reached the col at North Bay, and that for much more than half the length of Mattawa 

 River they had flowed through deep narrow lakes. It is certain, therefore, that they were free 

 from the coarser grades of sediment that might otherwise have been most efficient tools of 

 erosion. Probably, therefore, the amount of erosion accomplished by this river is relatively 

 small for the time it flowed. 



The relatively strong Nipissing beach at the head of the outlet and on the shores of modern 

 Lake Nipissing is also significant of the time involved, for at the time of the full discharge 



i Taylor, F. B., A reconnaissance of the abandoned shore lines of the south coast of Lake Superior: Am. Geologist, vol. 13, 1894, pp. 366-371. 



2 Taylor, F. B., The Nipissing-Mattawa River, the outlet of the Nipissing Great Lakes: Am. Geologist, Vol. 20, 1S97, pp. 65-66. 



3 Much detailed information concerning Mattawa River and its lakes may be found in the report of R. W. Ells and A. E. Barlow in The 

 physical features and geology of the route of the proposed Ottawa Canal between the St. LavTence River and Lake Huron: Trans. Royal Soc. 

 Canada, 1S95. The report gives table of altitudes and many soundings. 



4 In the writer's early paper (The ancient strait at Nipissing: Bull. Geol. Soc. America, vol. 5, 1893, pp. 620-626) an error was in some unaccount- 

 able way made both in the map and the text. The name "Nipissing beach" is there attached to a beach lying north of the water tower and having 

 an altitude of 743 feet, whereas the real Nipissing beach lies along the base of the bluff south of the water tower and has an altitude of 698 to 700 feet. 

 Unfortunately this error was repeated in a later paper (The second Lake Algonquin: Am. Geologist, vol. 15, 1895, p. 166). 



6 The scoured bowlders of the Mattawa Valley: Am. Jour. Sci., 4th ser., vol. 3, 1S97, pp. 20S-218. The Nipissing-Mattawa River, the outlet of 

 the Nipissing Great Lakes (abstract): Jour. Geology, vol. 5, 1897, p. 220; Science, Jan. 15, 1S97, p. 90. 



