v; jy. W. portion of Lake Huron, 2^65 



The crystalline grey or brown limestone of the Island of 

 Montreal, of the Falls of the Chaudiere on the river Ottawa J 

 and of the Falls of Montmorenci, and Point Aux Trembles 

 near Quebec, are examples of secondary strata assuming 

 the structure of the primitive class. Their fracture is slaty 

 in the large, and imperfectly conchoidal in the small. They 

 yield to the knife, but not to the nail. Their fracture-sur» 

 face is full of rhomboidal facets, and resembles that ofHorn- 

 blende. They are at the same time full of bivalves, turbi- 

 nites, branches of coral, of fibres of wood, and of srpall 

 drusy cavities of pearl-spar and yellow Bknde. 



A strong odour of sulphur is exhaled on percussion. 



The limestones of the North West portion of Lake Hu- 

 ron vary considerably in character and contents; and may 

 be divided into three principal species, viz. that of St. Jo- 

 seph and the islets on the north shore — that of the Manitou- 

 line Range and that of Michilimackinac. 



To commence with, that of St. Joseph, as being nearest 

 the elder rocks, it is of various shades of brown, which are 

 usually light. It is soft, knotty, schistose, and of an imper- 

 fect conchoidal fracture. 



It seldom shews itself in ledges of more than two yards 

 high, and then is much shivered; the fragments being lilunt, 

 and weathered. The lower strata are often of a greenish 

 tinge — not occasioned by decaying vegetables and only af- 

 fecting the surface, but also the deeper and sound portions. 

 This variety is remarkable for its number of what appear to 

 be clove brown shells, oblong, and of the size of millet seeds. 

 On Isle Vert, (six miles East of St. Joseph, and two from 

 north shore) this substratum rests upon a very dark blackish 

 brown limestone so schistose as to be in fact a shale, as tru- 

 ly so as that of Niagara. It contains no shells. It is under 

 water. Rhomboidal, pearl, and dog-tooth calc spar are the 

 only minerals I met with in this limestone. 



An enumeration of its organic remains is placed in the 

 appendix. I have to lament that I am not more familiar 

 with this interesting part of Geology. 



The Hmestones of the Manitouline Range although in part 

 on the same level with the species just described, differ 

 from it in many respects ; and thus themselves are not al- 

 ways the same. That a basin of secondary deposition, 

 should contain on the same level, rocks of different charac- 



Vor. nT,„..No. 2, 34 



