CLIMATE AND PHYSICAL CONDITIONS OF KEEWATIN 3 



crust or its downward extension. For example, Rosenbusch in 

 the new edition of his Elemente der Gesteinslehre speaks of the 

 crystalline schists underlying all later rocks as representing, at 

 least in part, the earth's erste Erstarrungskruste. 1 Like some 

 others of the older geologists he still holds to the Nebular Hy- 

 pothesis and looks on the basal complex as having been formed 

 at the stage when the molten earth had so far cooled as to consoli- 

 date on the surface, producing plutonic rocks' and crystalline 

 schists. According to this hypothesis it was still too hot to per- 

 mit the condensation of water, so that no rivers or oceans were 

 possible. 



Elaborate theories of continent- and mountain-building are still 

 founded on this idea of the earth's progressive cooling, and it is 

 hard for geologists brought up like the present writer on the fiery 

 diet of a Nebular Hypothesis as an introduction to historic geology 

 to rid their minds of so firmly imbedded a prepossession. That 

 astronomers also are afflicted with these bad dreams is plain from 

 certain recent popular writings on the history of Mars as com- 

 pared with earth. The conviction is however growing in the minds 

 of many geologists that even the pre-Huronian or Archaean can- 

 not be looked on as exceptional; that the Huronian basal conglom- 

 erate means a break in time, but no break in the continuity of 

 marine and terrestial processes ; that the affairs of the world were 

 conducted in the same way before this great interval as after it. 



Evidence of various kinds in favor of this will be given in sub- 

 sequent pages. 



THE KEEWATIN ERUPTIVE S 



"The basal complex" of the western lakes region was split 

 up many years ago by Lawson into the Laurentian granites and 

 gneisses and the Keewatin, the latter looked on as consisting essen- 

 tially of eruptives. In the original Keewatin region on Lake-of- 

 the-Woods eruptive rocks are in great preponderance, though 

 Lawson recognized the presence of subordinate amounts of sedi- 

 ments, which will be referred to later. 



These eruptives are chiefly basic — now mostly transformed 



*Op. tit., 35. 



