The Ottawa Naturaeist. 11 



division. Thus in a small volume called " Esquisse Geologique du 

 Canada," published in connection with the Paris Exhibition, 1855, in the 

 chapter relating to the rocks afterwards known as the "Quebec Group," 

 after describing the Hudson River division near Quebec city and the 

 overlying slates and conglomerates of Levis, F it is stated that " this 

 formation at Quebec is succeeded by red and green slates with thin 

 bands of calcareous matter, and intercalated towards the summit with 

 great masses of quartzose sandstone, often calcareous, and coloured by a 

 mixture of argillaceous matter which is greenish or reddish. This series 

 of sandstones and slates which has a total thickness of 1000 metres has 

 been named by Logan the Sillery group, and appears to be the equiva- 

 lent of that which has been named by the New York geologists the 

 Shawangunk or Oneida conglomerate, which in central New York lies 

 between the Richelieu slates and the Medina sandstone." 



Subsequently however the finding of Calciferous and Chazy fossils in 

 the beds overlying the Hudson River portion led to a change of view as 

 to the age of the Sillery and Levis rocks, and to their being placed in a 

 much lower position in the geological scale. The subsequent 

 detailed work on these rocks shewed that the Sillery grits and slates 

 were of the horizon of the Potsdam sandstone, while the Levis lime- 

 stones and slates associated, were Calciferous. As for the so-called 

 Hudson River division, then supposed to be the lowest beds of the 

 series, the work of Lap worth and Ami has shewn these to be presum- 

 ably about the horizon of the Black River and Trenton. 



It would thus appear that in connection with the Rensselaer beds 

 the order as proposed by Mr. Dale, may be subject to criticism ; more 

 particularly when we consider the work done by Sir Win. Logan in 

 this area, and the resemblance, in every particular, to the beds which we call 

 the Sillery and Levis in Canada, and which the work of recent years has 

 placed on a satisfactory basis. And it is interesting to note how the views 

 of structure concerning the northern extension of these beds in Canada, 

 abandoned forty years ago by Logan and his associates, have so lately 

 been put forward by our fellow geologists south of the line. This may 

 readily be regarded as a clear case of history repeating itself. 



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