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



Its neighbourhood has recently been survey ed^ preparatory to sale by the Go- 

 vernment of the United States. 



Sect. II. ON THE GEOLOGY OF THE COUNTRY BORDERING ON 



LAKEHURON. 



§ 1. ON THE ROCKS IN SITU. 



I will not apologize for the deficiencies that may be remarked^, nor for the 

 inaccuracies that future observation may detect in the following pages. They 

 are in a manner natural to the efforts of a first observer in an unknown^ vast, 

 and savage country. 



The northern shore of Lake Huron^ with its nearest isles, consists principally 

 of the older rocks ; the secondary occupy the rest of the lake. The primitive 

 rocks are part of a vast chain, of which the southern portion, extending pro- 

 bably uninterruptedly from the north and east of Lake Winnipeg*, passes 

 thence along the northern shores of Lakes Superior, Huron, and Simcoe, and 

 after forming the granitic barrier of the Thouraud Isles at the outlet of Lake 

 Ontario, spreads itself largely throughout the state of New York, and then 

 joins with the Alleghanies and their southern continuations. 



The geology of that part of this primitive chain which borders on Lake 

 Huron is but imperfectly known. I shall give such detached information 

 concerning it as I am possessed of. 



The French River flows over a granular gneiss at its source and mouth ; 

 and over red and feldspathic gneiss about the falls of the Recollet. Its shi- 

 vered and dislocated state, its mossy coating, and the astonishing quantity of 

 native debris prevented my ascertaining the direction of the strata, although 

 I landed more than once during my passage down the river. 



The low and sandy beaches of the south shore of Lake Nipissing are 

 crowded with mounds of gneiss unmixed with any other rock. The direction, 

 from its great irregularity, I was unable to determine. 



The rocks of the north coast, and its contiguous islands east from the French 

 River, consist of gneiss, with occasional mixture of hornblende f. 



From the French River westwards to the islands of La Cloche, about 60 

 miles distant, the lake near the shore is studded with innumerable islets. In the 

 first 20 miles they commonly consist of gneiss, are barren, and surrounded by 

 shoals, and are often, in fact, a heap of ruins. This is particularly the case 



* Vide Geological Transactions , vol. v. Part II. page 607. 

 t Communicated to me by Lieut. Grant. 



