MICHIGAN ACADEMY OF SCIENCE. 31 



of Port Huron, to the Ohio line in the southeast corner of Lenawee 

 county. An arm of this hike also extended north from Spring Hill fifty 

 miles to Ubly, which is at the head of its outlet. But this extension was 

 only a long, shallow, narrow bay, less than three and a half miles wide 

 at its mouth east of Spring Hill. The site of this bay is the present 

 valley of Black river. 



During the time of Lake Whittlesev the front of the ice sheet rested 

 on the Port Huron moraine which was then being built. This moraine 

 is a great ridge of clay hills extending from the north bank of Black river 

 six miles west of Port Huron northward and northwestward along the 

 east side of the river into Huron county, where it turns to the southwest 

 past Cass City and Caro to Vassar. Between these points it is landlaid 

 and is a rugged, prominent feature. South of Port Huron it is waterlaid 

 and is low and flat. It crosses the St. Clair river into Canada one mile 

 above the village of St. Clair. From Vassar westward it is also water- 

 laid and passes through the city of Saginaw. While Lake Whittlesey 

 filled the Erie-Huron basin in front of the Huron ice lobe the Saginaw 

 valley in front of the Saginaw ice lobe was also filled with another gla- 

 cial lake known as Later Lake Saginaw. The outlet of this last lake 

 was westward through the Grand River valley. These two lakes existed 

 at the same time and the ovei*flow from Lake Whittlesey entered Later 

 Lake Saginaw and made a large channel about eighteen miles long run- 

 ning southwest from Ubly to Cass City, descending in this distance, as 

 levels are now, about fifty feet. But the land has been tilted up at the 

 north a little since then, so that the descent at that time was probably 

 about one-third less. 



The existence of Lake Whittlesey was wholly dependent upon the pres- 

 ence of the ice sheet as a retaining barrier or dam. The ice sheet was 

 a solid, rock-like mass filling the whole bed of Lake Huron and part of 

 the Saginaw valley, its front resting all along on the Port Huron moraine. 

 About five miles north of Ubly the surface of the thumb begins to fall 

 away northward to Lake Huron, descending about two hundred feet 

 in eighteen miles. If the ice sheet had not existed as supposed, or if its 

 front had stood a few miles farther north, there would have been nothing 

 to keep Lake Whittlesey up to its level. Its waters would have found 

 free passage around the end of the thumb at the level of Later Lake 

 Saginaw, forming a strait between the waters on its two sides. 

 These facts and relations were clearh' made out in 189G.* 



The studies of 1904 brought out further facts bearing on the history 

 of Lake Whittlesey. Since it was discovered and named by Spencer 

 about eighteen years ago, the next beach below the Belmore has been 

 known as the Arkona beach. It has generally been described as a faint 

 and broken shore line. More recently Prof. W. H. Sherzer of Ypsilanti 

 found it in Monroe and Wayne counties with the same characters, but 

 represented by two ridges. It was found last season that in a certain 

 favorable locality this beach presents three well formed ridges with a 

 fourth fainter one above, possibly belonging to the same series. The 

 interval between the three strong ones is fifteen to eighteen feet, the 

 middle one lying a little above the mean. 



The Arkona beaches were found to sustain a remarkable relation to 



♦"Correlation of Erie-Huron beaclies witli outlets and moraines in Southeastern Michigan." Bulletin 

 Geological Society of America. Vol. S, 1S96. See also, "The great ice-dams of Lakes Maumee, Whittlesey 

 and Warren." American Geologist, Vol. XXIV. July, 1899. 



