377 



clearly how what he calls the Hudson River group came to be 

 conformable to the gneiss, with two unconformable and widely 

 different strata of great thickness interposed. Mr. Logan is of the 

 same opinion as Dr. Bigsby on the age of the strata in the vicinity 

 of Quebec, and moreover he gives an explanation of what puzzled 

 the Dr. so much. In his " Report of Progress for the year 1852-3," 

 p. 35 and 36, Mr. Logan explains the discordance of stratification 

 between the Trenton limestone and the Quebec bituminous black 

 and gray slates, by an anticlinal axis complicated by a fault. It 

 must be observed that Mr. Logan admits that he cannot give any 

 precise facts by which to determine the position of the anticlinal. 

 I quote his description of the Montmorency Falls section. 



" The details of the fault are well displayed at Montmorency Falls ; 

 here the channel of the river is cut down through the black limestone 

 beds of the Trenton formation to the gneiss of the anticlinal ridge, and 

 the water at and below the bridge flows down and across the gneiss, 

 and leaps at one bound to the foot of a precipice, which, immediately 

 behind the water, is composed wholly of this rock. At the summit of 

 the cascade, the Trenton beds on each side have a thickness of almost 

 fifty feet, and they are marked by Trinucleus concentricus, Calymene 

 senaria, Conularia quadrisulcaia, Leptcena sericcea, L. delloidea, Orthis 

 testudinai'ia, and Lingida. The dip of these beds is down the stream at 

 a very small angle ; but at the foot of the precipice, and in immediate 

 contact with the gneiss, about the same thickness of limestone is tilted 

 up to an angle of fifty-seven degrees ; it is followed by a similar amount 

 of black bituminous shale with the same slope ; in this attitude these 

 rocks climb up the face of the precipice, presenting their edges to the 

 chasm on each side. They are followed by about eight feet of strong 

 hard gray sandstone, weathering brown, in beds of ten to eighteen 

 inches, interstratified with black shales, to which again succeed gray 

 arenaceous-argillaceous shales, composing the sides of the chasm, out to 

 the waters of the St. Lawrence. The limestones belong to the Trenton, 

 the black shales to the Utica formation, and the gray to the Loraine 

 shales." 



When at Montmorency Falls, 28th Sept. 1849, I made the fol- 

 lowing notes. The fall is formed by a quartzite rock passing to 

 mica-schist (gneiss of Messrs. Logan and Bigsby) with traces of 

 substratification, and running east 20° north, to west 20"^ south ; 

 at the foot of the fall and in contact with the quartzite there is a 



