36 Reviews — Dr. A. C. Lawson — The Rainy Lake Region. 



It may be well to say that the matter first examined was sent to the 

 writer some years back by Mr. E. Waller, who worked with Mr. 

 Hyndman on the mollusca; and, secondly, from a quantity of Mr. 

 Hyndman's own washings, placed at his disposal by Mr. S. A. 

 Stewart, of Belfast. 



S, E "V" I E "W S. 



I. — Report on the Geology of the Rainy Lake Region. By 

 Andrew C. Lawson, M.A., Ph.D. Annual Report of the 

 Geological and Natural History Survey of Canada for 

 1887. Part F. 



THE progress of knowledge with reference to the foliated crystalline 

 rocks has been very rapid of late years, and accompanied by 

 incidents that may almost be described as sensational. One such 

 incident was the announcement by Mr. Lawson at the meeting of 

 the International Geological Congress, held in London, that the 

 Laurentian rocks in the neighbourhood of Rainy Lake were in- 

 trusive into a series consisting of schists, diabases, felsites, agglome- 

 rates, and greywackes. 



Up to the time of the announcement of Mr. Lawson's discoveries 

 it had been supposed that the Laurentian rocks were always older 

 than the rocks in contact with them, and the hunters after that 

 geological Will o' th' wisp, the primitive crust of the earth, were 

 beginning to feel tolerably satisfied that they had at last caught the 

 object which had hitherto eluded their grasp. It was seen at 

 once that Mr. Lawson's discoveries reopened the whole Laurentian 

 question, and made it possible if not probable that the so-called 

 Laurentian system was a complex, and that the most characteristic 

 rocks of the system — the gneisses — were plutonic igneous rocks, 

 actually of later date than rocks which have been formed by such 

 agencies as are now in operation at the surface of the earth. 



We have in the Memoir before us the details of Mr. Lawson's 

 work, illustrated by an admirable map of the Rainy Lake region, 

 and by photographs of actual junctions. A study of this Memoir will 

 leave no doubt in the mind of any geologist that Mr. Lawson has 

 fully established his main point, which is this — that over an area of 

 several thousand square miles the gneisses hitherto 1 regarded as 

 Laurentian have consolidated as such from a plastic magma long 

 after the formation of the rocks which encircle them. As this point 

 is one of great importance we will give a somewhat detailed account 

 of Mr. Lawson's work. 



The rocks into which the Laurentian is intrusive are divided by 

 the author into two series — the Coutchiching and the Keewatin. 

 The earlier or Coutchiching series consists mainly of mica-schists 

 and granulitic gneisses. The dominant constituents of the mica- 

 schists are granulitic quartz and biotite. The gneisses differ from 



1 The term Laurentian is still retained for these rocks in this Memoir. 



