[ells] CANADIAN GEOLOGICAL NOMENCLATURE 31 



obscure, has always been considered admissible, but does not quite 

 satisfy the conditions of the problem, regarding the true positions of the 

 different members which make up the whole series. Such names as 

 Couchiching, Keewatin,' Steep Eock series, Vermilion, etc., employed in 

 the study of the area west of Lake Superior, have been there well em- 

 ployed to distinguish certain groups of rocks, the structure and re- 

 lations of which have been observed in different localities ; but until 'a 

 correct idea can be had as to the true position of each of these, and of 

 their relations to each other and to the great underlying mass upon which 

 they now rest, as well as to the somewhat similar rocks in eastern Canada, 

 these additions to our nomenclature cannot be regarded as greatly enlarg- 

 ing our knowledge concerning the systematic structure of the whole. So 

 also the new term Algonkian, employed by some of the geologists of the 

 United States, for certain portions of this great group of crystalline 

 rocks, and which has not, hitherto, been readily accepted by Canadian 

 workers, does not afford much information as to the proper or satis- 

 factory settlement of this great question; while Azoic, Eozoic and 

 Archsean, terms which have also been applied from time to time, for the 

 whole or for portions of the crystalline rocks, can now be accepted as 

 applicable, only in the broader sense, to the rocks of the series as a 

 whole. 



That there was a first formed crust of the earth, on which all sub- 

 sequent rock formations have been deposited, is conceded by all. Such 

 original crust, wherever it may be found, may well be accepted as repre- 

 senting our oldest rock series; and in our present scheme of nomencla- 

 ture, may be safely assigned to the Laurentian division. This old crust, 

 presumably greatly modified from its original condition as a consolidated 

 mass, has been recognized over large areas, and in many widely separated 

 districts, throughout the northern portion of the Dominion. In this we 

 may reasonably include our first formed granites and syenites, which 

 from some cause have, since their formation, frequently assumed a 

 foliated structure to which the name gneiss has been applied; and in 

 these no trace of sedimentation or stratification has yet been discerned. 

 Upon this view our scheme for this portion, would coincide closely with 

 that laid down in 18:7-78, by Dr. Selwyn. 



Upon this there has been deposited, largely through the "agency of 

 water, a great series of formations, comprising gneiss, schist, quartzite, 

 limestone and conglomerate, which must evidently be assigned to a 

 higher position in the scheme. These must have been largely derived 

 from the decay and waste of the pre-existing crust; but they have in turn 

 been invaded by great masses of granites and other kinds of igneous 

 rocks, which have helped to swell their original volume greatly, and the 



