Geological Society. 133 



limestone, is, that the latter is in some situations in immediate con- 

 tact with gneiss ; while in others it passes into beds of the first series 

 above mentioned j of which the conglomerates contain organic re- 

 mains derived from the conchiferous limestone. 



1 . The slaty-series occupies the whole of the southern shore of the 

 St. Lawrence, the Island of Orleans, and a considerable portion of the 

 north bank of the river, including the ridge upon which Quebec is 

 placed. In that neighbourhood the mass of the deposit consists of a 

 black and brown slaty limestone, inclined at high angles, in some 

 instances nearly vertical j and alternating with semi-crystalline lime- 

 stone, and various conglomerates. The limestone contains several 

 varieties of crystallized carbonate of lime, intermixed with quartz 

 crystals, and occasionally traversed by seams of bituminous matter. 

 Near Cape- Rouge, and on the plains of Abraham and Kilgraston, 

 some of the strata consist of red and greenish clay-slate. In the cal- 

 careous conglomerates, organic remains are mixed with fragments of 

 clay-slate, and the beds alternate with compact gray limestone and 

 quartzose layers. Between Quebec and Cape-Rouge, boulders of 

 primary rocks, and fragments of compact grauwacke, are buried deep 

 in the red schist. 



The channels of the various streams east and west of Quebec, afford 

 instructive sections, which, according to the author, prove these slaty 

 deposits to be more recent than the conchiferous limestone. 



On the south side of the river St. Lawrence, the slaty limestone of 

 Quebec is no longer seen, but several new beds of conglomerate pre- 

 sent themselves ; one of the lowest of which contains trilobites, en- 

 crinites, corallines, and other fossils associated with vegetable impres- 

 sions, probably fuci and amansice. In the schistose beds near the 

 mouth of the Etchemin are thin seams of coal ; and at the village of 

 St. Henry the slate is so compact as to be used for hones. 



2. The horizontal conchiferous limestone occupies a zone from 

 two to three miles in breadth, on the north of the slaty tract, and 

 included between the slate and a mountainous range of gneiss. It is 

 exposed in the beds of all the rivers which flow southwards into the 

 St. Lawrence, and its characters are well developed at the falls of the 

 Montmorenci and the St. Charles, and at the quarries of Beaufort. The 

 organic remains consist of several species of trilobites, orthocerae, 

 terebratulae, encrinites, ammonites, &c. On the Montmorenci the 

 beds are from eighteen inches to two feet in thickness, nearly hori- 

 zontal, and of a blackish -brown colour j in one situation they pass 

 into a subjacent calcareous conglomerate, whilst in other places the 

 limestone itself contains large blue nodules, and reposes immediately 

 upon gneiss. At Beaufort-quarries, ledges of fetid limestone alter- 

 nate with calcareo-bituminous shale, containing organic remains 

 similar to those noticed on the Montmorenci. 



From the characters and fossils of the limestone above described, 

 the author regards it as the same with the calcaire intermediaire of 

 D'Aubuisson, or the equivalent of the " Carboniferous-limestone" of 

 English geologists. 



Dec. 21. 



