GLACIAL LAKE ALGONQUIN. 429 



region south of St. Marys River and the lower ground of the northern peninsula of Michigan, 

 and a view from it gives a very vivid impression of the great magnitude of the change in the 

 relation of the lake waters to the land and of the recentness of that event. But that the change 

 is really due almost wholly to differential elevation of the land rather than to the giving way 

 of a barrier is a conception which it is not easy to visualize. Here, also, Lawson's work was 

 instrumental. 



On the northern peninsula of Michigan as far west as Houghton, the Algonquin beaches 

 have been identified at several places by Mr. Leverett. Farther west in Michigan, Wisconsin, 

 and Minnesota the glacial features and old lake strands are now being studied by him in prep- 

 aration for a report on the Lake Superior region. In the western part of the basin the highest 

 beach of Lake Algonquin has not yet been certainly determined. 



The reconnaissance of the writer in the highlands east of Georgian Bay and in the Mattawa 

 and Ottawa valleys included in all probability some of the members of the upper Algonquin 

 group, but did not establish the identity in the north of the highest Algonquin of the southern 

 part of the Lake Algonquin area. 



In the region north of Michipicoten Bay, gravelly ridges found by Coleman lie very close 

 to the plane of the highest Algonquin produced from the south. One locality at Gonclreau Lake 

 20 miles west of Missinaibi, may possibly establish the extension of the higher levels of Lake 

 Algonquin to that place. 



The highest Algonquin beach at Sault Ste. Marie, at places on the northern part of the 

 northern peninsula of Michigan, and on Keweenaw Point are north of the isobase of Kirkfield, 

 and are therefore, in all probability, parts of the highest beach of the second or Kirkfield stage, 

 and are not strictly the same beach nor in the same plane as the highest Algonquin south of the 

 isobase. Nevertheless, nothing corresponding to this theoretical difference was seen in the 

 beaches at Sault Ste. Marie to distinguish them from those at Mackinac Island, except that the 

 vertical interval covered by the upper group as a whole is somewhat greater than at Mackinac. 

 Perhaps the site at Root River was still covered by the ice sheet when the Kirkfield outlet was 

 abandoned. These northern beaches would then belong to the third or Port Huron-Chicago 

 stage. No facts having a decisive bearing on these relations are known at the present time. 



Progress of investigations. — The upper group of Algonquin beaches, especially the highest 

 beach, shows the greatest amount of deformation by differential elevation of any beach in the 

 region of the upper Great Lakes. In his early work on the beaches in Ontario, Spencer used the 

 spirit level. Since that time, however, most investigators, including Mr. Leverett and the writer, 

 have used only the aneroid barometer and the hand level, and though results obtained by these 

 last two methods are serviceable for general purposes they are not accurate enough to settle 

 the relations of the planes of the different beaches or to determine the variations in the rate of 

 inclination of those planes. 



In 1905 Goldthwait made a detailed wye-level survey of the Algonquin and lower beaches 

 on the Wisconsin shore of Lake Michigan that served to correct some of the writer's earlier work 

 with aneroid and hand level. In 1907, under the writer's direction, Goldthwait made a similar 

 survey of the Algonquin and lower beaches on the east side of Lake Michigan extending from 

 the ancient Munuscong Islands north of Hessel to Holland. In 1908 he continued the work 

 under the writer's direction on the same beaches in Ontario, covering the east side of Lake Huron, 

 the south side of Georgian Bay, and the region of Lake Simcoe. 



Hobbs made instrumental surveys on the beaches of the Garden peninsula on the west side 

 of Lake Michigan in 1907, 1 and Gregory in the same year ran several lines across the beach 

 series on the west side of Lake Huron between Rogers and Harrisville. Gregory's report has 

 not yet been published, but in a brief summary of his work, communicated personally, he 

 describes the beaches by groups or "series" rather than by individuals, and does not always 

 clearly distinguish the different series, putting certain beaches into the first series in some 



1 Hobbs, W. N., Late glacial and postglacial uplift of the Michigan Basin: Publ. 5, Geol. ser. 3, Michigan Geol. and Biol. Survey, 1911. 



