32 PARALLELISM OF THE QUEBEC GROUP. 



of the trilobites Olenellus Vermontana, 0. Thompson!, &c. These 

 latter are primordial and belong to the Potsdam group. They 

 may very properly be placed in the Taconic system, but, they lie 

 far below the Quebec group. 



As Mr. Marcou can derive no aid from palaeontology in support 

 of his classification, he must establish it by physical geology. He 

 must point out some place where the Potsdam can be seen overlying 

 the Quebec group, as represented in his section. The locality 

 must exhibit the rocks in their natural position. There must be 

 no disturbances, such as faults and overturns. Now, at Quebec, 

 not only are the strata wonderfully contorted and faulted, but fur- 

 ther, Mr. Marcou says he could not find any Potsdam there at all. 

 He says on page 13 of his published letter to Barrande : 



" The Potsdam Sandstone does not exist in the district of Quebec, and 

 I did not see a single trace of it north of the Grand Trunk Railroad from 

 Richmond to Montreal. Probably if these rocks were ever deposited in 

 that region, not finding any point of resistance close by, as in the Adi- 

 rondack country, they slipped under all the other strata in the overturn of 

 the Taconic, and have been entirely concealed from view by the succeed- 

 ing groups." 



If the Potsdam be concealed from view at Quebec, how does he 

 know that it overlies the Quebec group ? In the above quotation 

 I have italicised a few words, because at p. 10 he informs Bar- 

 rande that the strata at Point Levis are not much disturbed, " and 

 that the few foldings in the strata of the Ferry Cliff, are mere ac- 

 cidents, confined to a distance of a few feet, and are without any 

 effect upon the whole mass of strata, but are, what we call in 

 French, structure ployie (contorted beds). This does not agree 

 very well with the asserted overturn. According to my view, when 

 a huge formation of rock, more than a mile in thickness, and occu- 

 pying many thousand square miles in geographical extent, has been 

 turned completely upside down (as Mr. Marcou says his new Ta- 

 conic system has been) by some tremendous convulsion of nature, the 

 structure must indicate a very considerable amount of disturbance. 



Passing now from Quebec to Phillipsburgh and Swanton, Mr. 

 Marcou, has given us another section to indicate the succession at 

 these two latter localities. It is as follows in descending order :. 



1. Potsdam sandstone, „ 300 feet. 



2. Swanton slates, 2000 " 



3. Phillipsburgh group, 1300 " 



4. Georgia slates, 400 " 



5. St. Alban's group, 3000 " 



