﻿482 Canadian Record of Science. 



study of these rocks, by the aid of the microscope, 

 has established their clastic character. 



As regards the sedimentary nature of the underlying or 

 Fundamental Gneiss, it has also been clearly shown that 

 the early view as to its origin cannot now be maintained, 

 but that these oldest of the Laurentian rocks are igneous 

 in their character and represent metamorphosed portions 

 of the original cooled crust of the earth. It would 

 appear, therefore, that in the Laurentian system there are 

 two distinctly separable series of rocks, viz., an altered 

 igneous or basal portion and an altered sedimentary or 

 upper portion (Logan's Grenville series in part), while the 

 original upper member of the system is relegated to a 

 different class entirely. 



The grey gneiss, limestone and quartzite of the 

 Grenville series represent, therefore, presumably, the 

 oldest series of clastic or sedimentary rocks on the 

 American continent. The term Grenville, like many 

 others which have appeared in Canadian geology, is 

 useful tor purposes of comparison, though great portions 

 of the rock masses which were originally included in this 

 series have in recent years been removed from their 

 original place in the scale. In the present use of the 

 terra " Grenville series " it is proposed to include only 

 those rocks concerning whose origin there is no doubt and 

 to confine the use of the term to the clastic members 

 of the series as far as this is possible. These have a wide 

 distribution throughout the Ottawa basin, and are 

 apparently continuous to the west with the series 

 described by Vennor in Ontario, nearly thirty years ago, 

 as the '•' Hastings series." > In character, however, many 

 of the rocks of the latter differ from those of the original 

 Grenville series. Thus, in the Hastings series, there is a 

 large preponderance of schists of various kinds, along with 

 dolomites and slaty limestones, which present a much less 

 altered aspect than is found in the limestones of the 



