NOMENCLATURE OF OTHER AUTHORS. 33 



which he had traced in Ontario. He therefore correlated the correspond- 

 ing Michigan beaches with those in Ontario and applied the same names to 

 them. Beginning with the highest, he called them the Ridgeway, Arkona 

 and Forest beaches. Another higher beach in Michigan he called the Mau- 

 mee. The Maumee and Ridgeway are almost certainly continuous with 

 Gilbert's numbers 2 and 3 in Ohio, but southward connection has not 

 yet been definitely established for Spencer's Arkona and Forest beaches. 

 Before the time of Spencer's work, N. H. Winchell had named Gilbert'.-! 

 numbers 2 and 3 the Leipsic and Belmore ridges respectively, supposing 

 them to be terminal moraines. These two names will be used here, but 

 Spencer's names for the two lower beaches, the Arkona and Forest, will 

 be retained. 



Spencer also made a reconnoissance across the southern part of the 

 Saginaw valley westward to Grand Rapids, and thence along the coast 

 of lake Michigan to Chicago. He found beaches and terraces in the 

 Saginaw valley which he correlated with those he had traced up from 

 Ohio. His map shows the lower three of the four beaches passing north- 

 ward around the end of the thumb to the Saginaw valley, while his 

 Maumee beach is shown as turning west across the thumb at Imlay, 

 leaving a large island to the northward ; but the island and the beaches 

 passing around the thumb are shown as hypothetical, for they were not 

 actually traced. Only two beaches are shown by Spencer in the Saginaw 

 valley. The upper one of these is made continuous with his Maumee, 

 but it was certainly not traced continuously, as we shall see presently. 

 Although Spencer traced two beaches into the long, deep trough of Maple 

 and Grand rivers extending westward across central Michigan, he did 

 not report the discovery of an old outlet. He called this valley the 

 Pewamo channel; but regarded it as holding only a strait and not a flow- 

 ing river. On the thumb the valley between the mainland and the hypo- 

 thetical island was also taken to be a strait. 



Topography. 



Almost the entire region under consideration is heavily covered with 

 glacial drift. Very few outcrops of the country rock occur except along 

 the present lake shore and in the beds of some of the larger streams. On 

 the thumb the coating of drift generally grows thicker inland. The great 

 Saginaw-Erie interlobate moraine, which is so well developed farther 

 south, extends only to the southern part of Lapeer county. One of its 

 highest points, 1,200 or 1,300 feet above sealevel, a little to the southeast 

 of Metamora, is the head of the interlobate, for at Dryden, nine miles east? 

 and at Imlay and Lapeer, northeast and north, the level is much lower 

 and the morainic deposit has lost its interlobate character. There is no 



