454 PKOCEEDLNGS OF THE GEOLOGICAL SOCIETY. 



Lake George, is succeeded to the eastward by the fossiliferous 

 limestone of Lake Huron, which rests in like manner on the pri- 

 mary rocks of the north coast, excepting for a few leagues at La 

 Cloche, where quartz-rock is interspersed between it and the older 

 rocks. This quartz-rock forms a range of hills, which are 

 considered to rise at least 1000 feet above the lake, and can be 

 seen towering over the Manitoulins from a distance of many 

 leagues. It also forms some of the islands between the Great 

 Manitoulin and the main land, where the limestone may be seen 

 overlying it in nearly horizontal strata. Although in some parts 

 highly crystalline, in others it is arenaceous, and passes into a con- 

 glomerate of great beauty, being studded with nodules, both 

 rounded and angular, of various coloured jaspers, quartz, calce- 

 dony, carnelian, &c. This rock occurs in immense cubical blocks ; 

 its stratification is obscure ; and its prevailing direction to the N.E. 



Dr. Bigsby, in a paper read before the Geological Society inl823*, 

 has given a description of the rocks and minerals of Lake Huron. 

 A recapitulation is here unnecessary. I shall merely observe, that 

 the primary beds and accompanying traps do not occur on the 

 same scale of grandeur as on the shores of Lake Superior ; they 

 are less elevated, more shattered, and less uniform in direction, 

 although the predominating strike is still to the N.E. An obscure 

 dip to the S.E., at a high angle, is discoverable occasionally, but 

 only when the structure of the rock is gneissose, which is more 

 often the case than on Lake Superior. The granitic compounds 

 very frequently contain hornblende. 



But the limestone of Lake Huron, like the sandstone of Lake 

 Superior, is a general formation over the whole lake. It is found, 

 as already observed, reposing on primary rocks at many points 

 along the northern shore from one extremity of the lake to the 

 other. It forms the large island of St. Joseph's, and the point of 

 land that separates the river St. Mary from the strait of Michili- 

 mackinac ; the S.W. coast as far to the south as Sagana Bay ; 

 the entire range of the Manitoulin Islands ; the great promontory 

 of Cabot's Head ; and the eastern coast fifty or sixty miles to the 

 southward and eastward of it ; and it probably extends much 

 further in that direction beneath the beds of sand and clay so 

 prevalent in western Canada. In Dr. Bigsby's paper already re- 

 ferred to, and in a paper read before the Society in 1837, will be 

 found an interesting description by Mr. C. Stokes of some of the 

 most characteristic fossils of this limestone, especially of the Ortho- 

 ceratites, and the museum of the Geological Society contains many 

 specimens from various localities. These, although probably far 

 from comprising a complete series, seem nevertheless sufficient 

 to enable us to assign to this limestone its analogous place among 

 European strata. Among those fossils we may point to the Spi- 

 rifer lynx (?) and Pentamerus oblongus, as indicating a consider- 

 able ascending range in the Silurian system of Mr. Murchison ; 

 and the numerous corals which were mostly found in the upper 



* Geol. Tr. 2d Ser. vol. i. p. 175. 



