1853.] BIGSBY — GEOLOGY OF aUEBEC. 91 



4. Red and green shales, titaniferous. 



5. Coarse-grained green sandstones, with more mica, and some 



plumbago. 

 This is an accurate statement in the general. It is the business of 

 this paper to give some of the minuter features of the district of 

 Quebec, features which I believe have not been published in detail by 

 Mr. Logan. 



In the course of this paper nothing more will be said of Utica 

 slate. The Hudson River Group will be described, first as it appears 

 in the promontory on which stand the city and suburbs of Quebec ; 

 and secondly, on the Quebec ridge, along the north shore of the St. 

 Lawrence. Then crossing the River St. Lawrence, the fine exposures 

 about Lauzon Pier and Point Levi will be noticed ; together with the 

 adjacent interior as far as the village of St. Henry. 



Quebec. — The great body of the Quebec promontory is limestone, 

 massed together in a thickness unusually great for the Hudson River 

 group. It is black, or brownish black, finely granular, dull and 

 conchoidal in cross-fracture; hardness variable; sp. gr. 2'5-2*7. 

 According to an analysis kindly made for me by Dr. Gerard Troost, 

 late State Geologist of Tennessee, it consists of — 



Carbonate of lime 78*0 



Alumina 15*5 



Coal and bitumen 6*5 



Parts. . . . 100-0 

 It is usually in layers a foot thick ; but, as it splits and shivers readily 

 when exposed to frost, it is often shaly, and is always a bad building 

 stone. 



On the surface of the natural cleavages there is usually a high 

 black polish, or a brown and red metallic glaze, like that of certain 

 English pottery, — an appearance very striking on the perpendicular 

 sheets of rock, of several hundred square feet, which form the face of 

 the precipice overlooking the west end of Champlain Street, Quebec. 



The strike of the great body of this aluminous limestone (see 

 fig. 4) is S.W. and N.E., with a very high dip to the S.E., conform- 

 ably to the Hudson River Group generally, and to many of the 

 crystalline ranges of the Canadas, not only hereabouts, but elsewhere. 

 But there are not a few abrupt deviations in strike, reversed dips, and 

 flexures, affecting considerable spaces together. The deviations are 

 mostly on the N.W. skirt of the promontory, and are almost always 

 at right angles with the ordinary strike. The small anticlinals and 

 foldings are evidenced by vertical strikes being flanked by opposing 

 dips. There are several visible in diff'erent parts of the city, but 

 sometimes obscured by the encumbered state of the ground. 



The most extensively exposed set of wavy flexures is in Sault au 

 Matelot Street, Two of the layers here open and leave a lenticular 

 interval, about 25 feet long, and filled with black limestone in one 

 amorphous mass, veined with calc-spar. Most of the great devia- 

 tions in strike or dip are comprised in the following list, and are 

 marked in fig. 4. 



