OF THE NOKTHWESTERN STATES. 19 



have been observed at various elevations up to eighty feet, which eorresponds closely 

 with the surface of the drift across the valley of the outlet of this lake at St. Mary's. 

 At Eagle harbor there are eight of them within a distance of one hundred and 

 ten rods, as represented in the accompanying profile. They may be seen around 

 the head of Green bay, within twelve to fifteen feet of lake level, containing the 

 same shells which now inhabit the waters of the bay. The distinctive feature of 

 the alluvial beaches, as compared with lake ridges, is that the former are narrow 

 and are steepest on the lake side, resembling miniature terraces. The materials 

 are also different, being not distinguishable from the clean beach sand and shingle 

 of the present water line 



Fig. 8. 



Pbofile of Ancient Lake Beaches, Eagle Haebor, Lake Supekioe. 



In the prairie region of Illinois, Wisconsin, Iowa, and Missouri, the general sur- 

 face is very uniform, and but little elevated above the northern lakes. A rise in 

 Lake Michigan of twenty-six feet would turn its waters across the summit into the 

 Illinois river. The country around Elgin on the Fox river of Illinois, is from one 

 hundred and sixty to two hundred feet above this lake, or seven hundred and fifty 

 to nine hundred and ninety above the ocean. Around Galena the summits of the 

 hills are seven hundred and fifty to nine hundred and ninety feet above tide. 



The rolling prairie opposite St. Louis in Illinois is not materially different, and is 

 nearly on a level with the region above Peoria. This general level stretches away 

 up the Missouri river to the northwest corner of the State of Missouri, and up the 

 valley of the Desmoines in Iowa to the centre of that State. The central parts of 

 the lower peninsula of Michigan rise only seven hundred and fifty to eight hundred 

 and fifty feet above tide, and the summit between the Maumee river of Lake Erie 

 and the Wabash, is between those figures. On the east the Alleghany mountains 

 from Alabama to New York, rise from two thousand to six thousand feet ; but in 

 the vaUey of the lakes the way is open eastward to the ocean. 



The rocky strata around the east end of Lake Erie present no barriers, since they 

 rise but a few feet above the lake level. Between Lakes Erie and Ontario the 

 present surface of the drift rises no higher than ninety feet above the mean level 

 of Lake Erie. The Erie canal is fed from Lake Erie by a moderately deep cut in 

 drift and rock, carrying the same level to Lockport on the bluff facing Lake Ontario. 

 Between the Georgian bay on Lake Huron and Lake Ontario, the summit is occu- 



