XV.] CAMBRIAN AND SILURIAN IN NORTH AMERICA. 397 



black powder, and results apparently from the alteration of 

 a once liquid bitumen. (American Journal of Science (2), 

 XXXV. 163.) 



In 1842 the geological survey of Canada was begun by Sir 

 "William Logan, who in a Preliminary Report to the govern- 

 ment, dated in that year but printed in 1845, says (page 19) : 

 " Of the relative age of the contorted rocks of Point Levis, 

 opposite Quebec, I have not any good evidence, though I am 

 inclined to the opinion that they come out from below the flat 

 limestones of the St. Lawrence." He however subsequently 

 adds, in a foot-note, " The accumulation of evidence points to 

 the conclusion that the Point Levis rocks are superior to the 

 St. Lawrence limestones." In 1845, Captain, now Admiral 

 Bayfield maintained the same view, fortifying himself by the 

 early observations of Bigsby, and expressing the opinion that 

 the flat limestones of Montmorenci and Beauport passed be- 

 neath the graywacke series. These limestones, from their 

 fossils, were declared to be low down in the Silurian, and 

 identical with those which had been observed at intervals 

 along the north shore of the St. Lawrence to Montreal (Geol. 

 Journal, I. 455), the fossiliferous limestones of which were 

 then well known to belong to the Trenton group of the New 

 York system. The graywacke series of Quebec, which was 

 still supposed by Bayfield to hold in its conglomerates fossils 

 from these limestones, was therefore naturally regarded as 

 belonging to the still higher members of that system ; and, as 

 we have seen, the green sandstone near Quebec, a member of 

 that series, had already, in 1842, been regarded by Emmons as 

 the representative of the Oneida or Shawangunk conglomerate, 

 at the summit of the Hudson River group of New York. 



It is to be noticed that immediately to the northeast of 

 Quebec, rocks undoubtedly of the age of the Utica and Hud- 

 son River divisions overlie conformably the Trenton limestone, 

 on the left bank of the St. Lawrence ; while a few miles to 

 the southwest, strata of the same age, and occupying "a similar 

 stratigraphical position, appear on both sides of the St. Law- 

 rence, and are traced continuously from this vicinity to the 



