36 ROYAL SOCIETY OF CANADA 



elsewhere intervene, has never been deposited in this area, since the 

 basal beds of the Potsdam are composed largely of the débris of the 

 Grenville and Hastings rocks. 



Comparing the Grenville and Hastings series of the east with those 

 styled Couchiching and Keewatin in the west, it may be said that while 

 the former resembles most closely the Grenville rocks, the Keewatin 

 presents certain features more generally found in the rocks of the 

 Eastings series. As for the relations of the Hastings and Grenville series 

 themselves, it is now considered by those most recently engaged in work- 

 ing out this problem, that the latter represents some portion of the 

 Hastings, in a generally more highly metamorphic condition, while the 

 latter from its position nearer the centre of the basin, has apparently a 

 greater thickness of strata, some of which do not appear in the portion 

 found in the more immediate vicinity of the Ottawa River. 



Following the studies of Lawson in the west, the detailed study and 

 mapping of the several divisions of the crystallines of the Ottawa dis- 

 trict and the area further to the west, where the original investigations 

 on the rocks of the Hastings series were commenced nearly forty years 

 ago, were soon undertaken by several workers, principally by Messrs. Bar- 

 low and Adams in Hastings and Haliburton, and by the author in the 

 area east of the Ottawa and in Eenfrew county, west of the river. The 

 observations which have been carried out systematically over a very 

 large area for some years have now reached a point when satisfactory 

 conclusions can be arrived at. In the area west of the Ottawa the 

 conditions, as already intimated, appear to very closely resemble those 

 described by Lawson for the country west of Lake Superior. There 

 is always the association of upper gneiss and schists described in the 

 Couchiching, with areas, often of large extent, of what appear to be 

 the underlying Laurentian granite-gneiss, but in the eastern district 

 there is also a very large development of crystalline limestone, quartz- 

 ites and sometimes slaty rocks, which are a part of the upper series. In 

 many of these places the granite has cut through the limestone and 

 other members, precisely as has the anorthosites of the Ottawa and St. 

 Jerome district. In other cases the limestone and associated gneiss ap- 

 pear to have been thrust aside and the disappearance of certain mem- 

 bers is probably due to unequal denudation and sometimes to squeez- 

 ing. 



In order to explain this feature of the association of the two series 

 of upper and lower gneiss, a theory was put fonvard by Barlow and 

 Adams, in a paper read before the Geological Society of America in 

 1897. In this, the view was taken strongly corroborative of that ad- 

 vanced by Lawson. The rocks of the Grenville and Hastings series 



