46 NEW YORK STATE MUSEUM 



Upham/ at a depth of more than 400 feet below Lake Erie. Whether 

 this marks the former southward continuation of the preglacial 

 Dundas river or whether that river turned more to the west, follow- 

 ing in general the course of the present Maumee, must for the pres- 

 ent remain unsettled. The Dundas undoubtedly became eventually 

 tributary to the Mississippi. 



Preglacial Saginaw river. The existence of an ancient river, 

 flowing southwestward from the Canadian old-land across the valley 

 of Lake Huron and the lower peninsula of Michigan, and finally 

 becoming tributary to the ancient Mississippi, is indicated by the 

 present character of the topography of that region. The Niagara 

 cuesta is breached by a deep channel which now connects Georgian 

 bay with Lake Huron, and which, north of Cove island, an outlier 

 from the Indian peninsula, has been sounded to a depth of over 300 

 feet. This channel is in direct line with that of Saginaw bay, and, 

 though this latter is at present very shallow, borings at Bay City 

 show an absence of rock to a depth of at least 200 feet below the 

 surface of the bay. At Alma (Mich.) the rock was shown to be 

 absent to a depth of 350 feet below Lake Huron (Spencer); and, 

 as this locality lies to the southwest of Saginaw bay and in line with 

 the trend of its axis, we may assume that our preglacial Saginaw 

 river was located here. Our limited knowledge of the preglacial 

 topography of this region forbids tracing this channel beyond this 

 point. Dr Spencer many years ago traced out this line of drainage, 

 but he assumed that the river which occupied this channel, and 

 which he has named Huronian, flowed northeastward to join that 

 part of the ancient St Lawrence, or Laurentian river, which he sup- 

 posed to have occupied Georgian bay. 



Preglacial consequent Genesee river. Among the numerous con- 

 sequent streams which flowed from the old-land southward or 

 southwestward and which eventually became tributary to the pre- 

 glacial Mississippi, probably through the ancient Ohio,^ the pre- 



^Bul. geol. soc. Am. 8: 7. 



^Westgate, Lewis. Geographical development of the eastern part of the 

 Mississippi drainage system. Am. geol. 1893. 11:245-60. The Ohio, ac- 

 cording to Newberry, flows nearly throughout its entire course in a 

 channel, the rock bottom of which is nowhere less than 150 feet below- 

 the present river. The rocks at the " falls of the Ohio " show that at that 

 point the river is not following the ancient course. 



