3fesozoic and CcKnozoic Geology and Palcaontology. 303 



Manistee, where it does not generally reach more than 4 or 5 feet above 

 the river, although in one place it was found 10 feet thick. It is ver^' 

 tough, and generally flesh colored, but in one instance it was perfectl}' 

 white. There were observed, in several localities, rather coarse pebbles 

 of limestone, and even flat stones intermixed with the upper layer of 

 cla}', near its contact with the sand. 



He described the terraces on the island of Mackinac and the neigh- 

 boring coasts, on the west coast, and at Pointe St. Ignace and Gros 

 Cap on the north coast of Lake Michigan, which varj' in height from 

 20 to 130 feet. But the terraces are not found farther west on the 

 north shore of Lake Michigan and Green bay, nor in tiie vicinity of 

 the Menomonee and Manistee. 



Mr. Charles Whittlesey,* said of the terraces bordering Lake Erie, 

 that the first ridge, or that nearest the lake, is known as the " North 

 ridge." From Conneaut, in Ashtabula county, to Russelton, Huron 

 county, a distance of 120 miles, the elevation of the ridge above the 

 lake varies from 85 to 145 feet. The second ridge, from Kingsville, in 

 Ashtabula county, to Ridgeville, in Lorain county, varies from 122 to 

 168 feet above the lake. These ridges consist of coarse, water-washed, 

 yellowish sand, or of fine gravel, principally the comminuted portions of 

 the adjacent rocks. The rocky fragments are not generally worn per- 

 fectly round, or oblong, as beach shingle is, but are more flat, with 

 worn edges. There are mingled with the sandstones and shales that 

 compose this gravel, scattered pieces of quartz, flint, granite, trappean 

 rocks, limestone and ironstone. The third and fourth ridges are a 

 little higher, and composed of coarser material. 



In 1852, Charles Whittlese}"! described the drift in that part of Wis- 

 consin bordering on Lake Superior, and ly'n\g between the Michigan 

 boundary and the Brule river, and the sources of the streams flowing 

 into Lake Superior from the south. He divided the drift into — 1st, 

 red marly clay; 2d, bowlder drift, coarse sand and gravel. 



The red marly clay is a fine-grained, homogeneous marl}^ sand, 

 cemented by argil or clay, with well defined horizontal lines of lamina- 

 tion or deposition; containing, but very rarel3% pebbles of granitdid, 

 trappose, sandstone, conglomerate, or slate rocks. This constitutes the 

 shore or lake bluffs most part of the way from the Montreal to the 

 Brule; the red sandstone, on which it rests, showing itself occasionally 

 beneath. It is easily washed away in suspension by the waves, and 



* Am. Jour. Sci. and Arts, 2d ser., vol. x. 

 t Owen's Geo. Sur., Wis., Iowa, and Minn. 



