330 H. C. COOKE 



limestones. Vennor, however, resigned from the Geological 

 Survey in the next year and his report was never published. In 

 1885, A- C. Lawson published the results of his work in the Rainy 

 Lake region, and demonstrated conclusively that the gneisses 

 there, previously known as Laurentian, were not sedimentary 

 rocks at all, but intrusive; and that, whatever the origin of the 

 gneissic textures, they could not possibly be accounted for as 

 reHcs of original bedding, since the rock had clearly been fluid 

 enough at one time to permit of the movement through it of frag- 

 ments of Keewatin. In 1887 he expressed the view that the 

 foliation was due to fiowage movements prior to complete solidifi- 

 cation. He also considered that the granite gneisses represented 

 the fused floor on which the Keewatin and Couchiching rocks had 

 been laid down, and definitely reparated the term Laurentian to 

 apply only to the intrusive gneisses. In the same year F. D. 

 Adams anounced in the Summary Report that his study of the 

 anorthosites north of the St. Lawrence River had shown that the 

 gneissic and massive portions were gradational into each other, 

 so that there was little doubt but that the whole body was of 

 igneous origin. A second statement to the same effect was made 

 by him in the Summary Report of the Geological Survey for 1891; 

 but his full report on the subject was not published till 1894. 

 A second report published in 1895 discusses the question of the 

 Lower Laurentian in the district north of Montreal, previously 

 subdivided into the Ottawa gneiss and the Grenville series; and 

 shows that gneissic structures may have originated in many ways 

 other than by original bedding, and that much of the gneiss here, 

 particularly the Ottawa gneiss, is of igneous origin, although 

 gneisses are present also whose composition indicates that they are 

 altered sediments. 



From this time it was generally recognized that the granite 

 gneisses are of igneous origin, not sedimentary, and as the sedi- 

 mentary parts of the old Laurentian series were already known 

 in the literature as the Grenville series, the name Laurentian was 

 restricted to its granitic parts. In many places, particularly in 

 Canada, the name was indiscriminately applied to any pre- 

 Cambrian granite of unknown age; but south of Lake Superior, 



