1853.] 



BIGSBY — GEOLOGY OF aUEBEC. 



89 



argillaceous and quartzose, loses nearly all its fossils, and assumes 

 a soft shaly structure, with a high dip to the S.E., — the same which 

 prevails for more than 100 miles in every direction but due north. 



Looking up, from below, at the higher parts of this bowl-shaped 

 chasm on the east side, we see, peeping from beneath rubbish and 

 among shrubbery, displaced slabs of compact Trenton limestone, fol- 

 lowed downwards by dark shales, while the lower parts of the preci- 

 pice and the beach of the River St. Lawrence are wholly occupied by 

 Utica slate in the full development of its crumbling rusty brown 

 shales, its Graptolites and Triarthrus Beckii, the Trenton fossils 

 having disappeared. 



Beauport. — Continuing our observations both on the Trenton lime- 

 stone and its connexion with Utica slate, it is to be noted that at Beau- 

 port, the village a little westward of Montmorenci, the change is well 

 displayed. 



Two hundred yards north of Col. de Salaberry's house in this 

 village, we have in a quarry the genuine horizontal Trenton limestone. 

 At oxAj ffty yards north of the house,' it is interstratified largely 

 with black shale, and with a slight dip. In the streamlet close to 

 the house, the rock is the true Utica slate dipping at a high angle 

 to the S.E. (Capt. Skene, R.E.). 



In the quarries about this village the Trenton limestone is full of 

 shale, often coated with fluor-spar, copper pyrites, and calcedony. 

 The bituminous druses are numerous, and often of the size of a 

 walnut. Its fossils are scattered in patches ; sometimes they are 

 altogether absent, at others in inconceivable quantities. Some of 

 the shaly layers are wholly composed of Trilobites (especially of the 

 Asaphus gigas), or oi Rhynchonella hemiplicata. 



Fig. 3. — Section at Petite Ruisseau R., showing the relation of the 

 Utica slate to the Trenton limestone. 



Trenton limestone. 



Talus, &c. 



R. Petite Ruisseau. — On the Petite Ruisseau, Avhich falls into the 



