84 Notices of Memoirs — Dr. Ells — Problems in Quebec Geology. 



sedimentary origin, it has been very conclusively demonstrated, 

 chietly through the agency of the microscope, that this is for the 

 most part at least an altered igneous rock, and that the supposed 

 bedding planes owe their existence to other causes than those of 

 sedimentation. 



The original Upper Laurentian division, which included the great 

 area of the Anorthosite rocks, also supposed at one time to represent 

 altered sedimentary deposits, has been removed from the position it 

 once occupied, since it has been proved, both by the evidence in the 

 field and in the laboratory, to be of igneous origin and subsequent to 

 the deposition of the limestone and quartzite series with which it is 

 associated, so that the Grenville Series, according to the earlier 

 view as to the succession of strata, may now be taken to represent 

 the upper portion of the Laurentian system. 



It may also be assumed to represent the lowest division of the 

 clastic or sedimentary rocks in Canada. The relations of these 

 to the rocks which have been styled the " Hastings Series " in 

 Ontario are such that they may, in part at least, be regarded as 

 portions of the same series which have been described in different 

 portions of the field under different names ; but whether these be 

 regarded as belonging to the Laurentian or Huronian systems, is 

 of small moment so long as their true relationship to each other 

 and to the underlying Fundamental Gneiss is clearly understood. 



To the east of the St. Lawrence the old dispute as to the age 

 of the fossiliferous rocks near the city of Quebec, as well as of their 

 relations to the crystalline schists of the mountain area in the 

 interior of the province, may now be considered as satisfactorily 

 settled. The former hypothesis by which the crystalline schists 

 ■were regarded as the equivalents, in point of time, of the 

 fossiliferous sediments of the St. Lawrence Valley has been clearly 

 shown to be unfounded, and the schists of the Sutton Mountain 

 area are now assigned to the Huronian system, or are at least 

 beneath the lowest Cambrian of the district. The relative position 

 of the several divisions of the fossiliferous Quebec group has also 

 been ascertained, and it is now established that the Sillery division 

 is situated stratigraphically beneath the Levis, instead of being, 

 as was at one time supposed, above it. As regards the age of 

 the several divisions of the Quebec group (fossiliferous), it may 

 be said that the Levis is the apparent equivalent of the Calciferous 

 formation, and that in its upper portion it approaches the Chazy ; 

 while the upper portion of the Sillery is the apparent equivalent 

 of the Potsdam Sandstone formation. Between the upper Sillery 

 and the great mass of the rocks which have been referred to this 

 division, there is a fault of considerable magnitude, so that the 

 lower portion of the Sillery presumably includes rocks which have 

 been elsewhere classed as Cambrian, and these may extend as low as 

 the Paradoxides zone or division of that system. 



The areas of black slate and limestone, which, in the General 

 Eeport for 1863, were regarded as beneath the crystalline schists 

 and referable to the Potsdam formation, have been determined, on 



