limestone ''differ in no way either in constituent quality 

 or diversity of arrangement from the gneiss lower down." 



Subsequently this lower gneiss was called the "Ottawa 

 Series" while the upper group, differentiated in the first 

 place solely on account of the presence of the limestones, 

 was included under the name Middle Laurentian or 

 "Grenville Series." He afterwards found in Eastern 

 Ontario a series of rocks which he considered in all proba- 

 bility to represent the Grenville series in a less altered 

 state and to this he gave the name of the "Hastings 

 Series." The foliation of the gneisses was regarded by 

 him as the survival of an almost obliterated bedding. 

 The name Upper Laurentian was given to a terrane formed 

 chiefly of anorthosites which were afterwards shown to 

 be of irruptive origin, and with which were classified by 

 mistake certain gneiss and limestone bands identical in 

 character with those included as the Grenville series, to 

 which they clearly belong. For many years very little 

 light was thrown upon the relations of the Grenville series 

 and the Ottawa series or "Fundamental Gneiss" as it was 

 frequently called. The relationship of the Grenville and 

 Hastings series also remained a matter of uncertainty. 



In 1885 Dr. Andrew C. Lawson showed the presence 

 in the region north-west of Lake Superior of great bodies 

 of foliated granitic rocks forming the base of the geological 

 column and the equivalent of the "Fundamental Gneiss" 

 of Logan. This gneiss, as Lawson conclusively demon- 

 strated, is intruded through the oldest sedimentary rocks 

 (Keewatin group) of that region in the form of great 

 batholiths. This work marked an epoch in the interpre- 

 tation of Pre-Cambrian geology not only in Canada 

 but in all North America. 



Then followed, in 1893, Adams' demonstration that 

 Logan's "Upper Laurentian" did not exist as an inde- 

 pendent geological series, the anorthosites, which were 

 considered as constituting its main features, being in 

 reality great intrusive masses. In a subsequent (1895) 

 paper he showed that two distinct classes of rocks could 

 be distinguished in the remaining portion of the Laurentian, 

 the first being beyond all doubt igneous rocks and the 

 second consisting of highly altered rocks of aqueous origin. 



From the results of these investigations, it became 

 evident that if a satisfactory knowledge of the origin, 

 character, structure and relations of the Laurentian 



