Dr. BiGSBY on the Geography and Geology of Lake Huron. 177 



Huron, and coasted in a canoe the north main of the latter lake to the Falls of 

 St. Mary. I have been several times on the south coast, and off the Gulf of Sa- 

 guina. The rest of the lake I know only from the communications of my friends. 



The accompanying Map is a reduced copy, with additions, of one of four 

 times the size, compiled by David Thompson Esq. British Astronomer under 

 the 6th and 7th Articles of the Treaty of Ghent, from surveys made by him- 

 self, and by Captain Owen, R.N., and from a map of the lake by Mr. Smith, 

 late Surveyor General of Canada. Mr. Thompson, assisted by the American 

 Astronomer Mr. Bird, and party, himself surveyed the north-western arm of 

 the lake and the Manitouline Isles as far east as the river Missasaga and the 

 western end of the Grand Manitou. He also determined the position of the 

 False and True Presquisles, Point aux Barques, the commencement of the 

 River St. Clair, Cape Hurd, the fourth Manitou, Point Colles, and the Hill 

 Islands. Captain Owen's survey comprehends Cabot's Head and its vicinity. 



I have added the Georgian Bay and the Straits of Michilimackinac from 

 Purdy's map of Cabotia, and part of Lake George from my own knowledge. 

 I have omitted many islands on the north shore, between the French and 

 Missasaga rivers, from their positions not being yet determined. Mr. Smith's 

 map is only to be trusted in a very general way ; the printed maps of the Lake 

 are very erroneous. 



I shall now describe those parts of Lake Huron which have been just enu- 

 merated. 



The appellation of " Manitouline" or " Sacred" Isles is first observed in 

 Lake Huron ; and thence westwards is met with in Superior, Michigan, and 

 the vast and numerous lakes of the interior. 



The islands of that name in Lake Huron are four in number, Drummond, 

 the Little, the Grand, and the Fourth Manitou, exclusive of the Isle of Coves, 

 and the other fragments of the great ridge that appears to have been once 

 continuous to Cabot's Head. They form a curving line 125 miles long; the 

 direct distance between the extremes being only 97 miles. 



Drummond Island is 24 miles long, and (on the average) 8 miles broad : the 

 greatest breadth being 12, and the least 2^ miles. It ranges nearly east ; and 

 at the western end approaches the main of the United States, there forming, 

 with the opposite headland, the strait of the True Detour, the principal com- 

 mercial route to Lake Superior. The strait is scarcely a mile wide, and, being- 

 bounded by two promontories, is of very small extent. The coast of the 

 United States is here flat and woody, with morasses ; that of the island is un- 

 even, and loaded with large fragments of rock. The general surface of 

 Drummond is irregular ; the higher and middle parts rising to the height of 



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