1845.] 589 



beds of Drummond Island and the other Manitoulins, would, lead 

 us to the same probable conclusion. 



_ And this is what we ought to expect when we consider that this 

 limestone, although termed horizontal, is not strictlj so. In the 

 comparatively small space which the eye can take in at a near 

 view it appears so ; but when we view the islands with their cliffs 

 as a whole, from a distance, or observe the gradual ascent of the 

 limestone plains as we proceed inland over the barrens on the 

 south side of the Great Manitoulin, and their gradual descent 

 under the waters of the lake in the contrary direction, we perceive 

 that there is a dip to the southward of some feet in a mile, which, 

 continued for 100 miles or more, must give a very considerable 

 thickness of strata. 



From the eastern extremity of Lake Huron, and still advancing 

 eastwards, we trace the Silurian limestone with similar fossils, 

 across to Lake Simcoe, to the Rice Lakes, and, on the north of 

 Ontario, to Kingston and the Thousand Islands*, and thence 

 again, north-eastward by Perth, Bytown, and Lake Chat, across 

 the Ottawa River f to Montreal and Quebec. It may also be 

 seen at various intermediate points along the northern side of 

 the valley of the St. Lawrence. At Port aux Trembles for 

 instance, about six leagues above Quebec, we find it containing, 

 among other fossils, Calymene Blumenhachii, and a species of 

 Chmtetes, which M. de Verneuil informs me is allied to C. petro- 

 politanus. The limestone here dips to the S. E. conformably to 

 the grauwacke, which contains Leptana sericea, on the opposite 

 or southern shores of the river. This latter circumstance, to- 

 gether with the statements of an anonymous writer in the 

 Canadian Review |, that the limestone near the falls of Mont- 

 morenci declines gradually from the horizontal position till it 

 finally dips at a high angle beneath the grauwacke ; and that a 

 conglomerate, wholly composed of re-cemented fragments of lime- 

 stone containing the organic remains peculiar to Beauport, the 

 falls of St. Charles, and Indian Lorette, is one of the alternating 

 members of the grauwacke and slate series, incline us to assign to 

 .this limestone a position inferior to the grauwacke and slate, and 

 low down among the Silurian strata. This view is strengthened 

 by the occurrence of a similar limestone on Lake St. John under- 

 lying clay slate, and containing Isotelus gigas and an Ormoceras, 

 like those of Lake Huron, &c. Considerable difficulty, however, 

 has been felt in admitting this, because the limestone has so very 

 generally been found in nearly horizontal strata, resting imme- 

 diately on primitive rocks in very near neighbourhood to the highly 



* Here, and also near Kingston, masses of sulphate of strontia and calc-spar 

 with disseminated iron pyrites and sulphate of zinc, are found in the limestone.' 



f On the Ottawa, above Lake Chat, and also on the St. Lawrence, near 

 Gananoqui, primary white granular limestone occurs extensively, associated with 

 green serpentine, steatite, compact and fibrous asbestus, and occasionally contain- 

 ing, as I am informed by Mr. Tennant, brucite, tremolite, plumbago, and mica. 



I In an article in the second number attributed to Dr. Bigsby, and published 

 some years ago. 



