DISTRIBUTION AND RELATION OF THE ARCHEAN ROCKS. 335 



means of transport by canoes. The lakes vary in size from mere ponds 

 to great island-dotted sheets of water, of which the largest — the Lake of 

 the Woods — embraces within its shore lines an area of hardly less than 

 six thousand square miles. Probably one-fourth of the whole area is 

 occupied by water. Tbe land surface presents a tumbled and irregular 

 succession of low, rounded hills, with here and there a sharp ridge or 

 steep escarpment, but bold and rugged scenery is extremely rare. The 

 surface has .a gentle average slope from the watersheds to the drainage 

 basins, and it is doubtful if the top of the highest hill is over seven hun- 

 dred feet above the bottom of the lowest and deepest lake. This area 

 occupies the southern margin of the Arctic basin. 



Present Status of the Investigations. — A description of tbe distribution of 

 the various rocks would be tedious and incomprehensible without con- 

 stant reference to a good map. A large portion of the area is depicted 

 on maps already published by the Canadian Geological Survey. A re- 

 port upon and map of part of the remainder have been prepared by the 

 writer and are now in press, while topographic and geologic materials 

 relating to still another portion of the remainder have been collected and 

 are now being prepared for publication. In addition to this, the writer 

 has made several preliminary reconnoissances and surveys in those por- 

 tions in which the field-work is incomplete. 



Distribution and Relation of the Rocks. 



Without entering into the details of rock distribution, there is one im- 

 portant feature of it which is worthy of attention. 



TIFO GREAT DIVISIONS AXD THEIR EXTENT. 



Lower Archean Series. — Separating tbe rocks for the present into two 

 great divisions, (1) the lower granitic and syenitic rocks, more or less 

 massive, and (2) the upper micaceous, hornblendic and trappean rocks, 

 for the most part distinctly schistose, we find that the former occupy 

 large rounded or ovoid areas which sometimes anastomose and the 

 peripheries of which approach each other to within comparatively narrow 

 limits. The longest axes of these areas are rudely linear to and parallel 

 with each other and have a general northeast or east-north direction. 

 In geographic extent these granitoid 'rocks cover considerably more than 

 halt of the whole country. It is interesting to note that such nuclear 

 areas of granite are reported by Barlow north of Lake Huron and are 

 mapped by Hitchcock in New Hampshire. As we pass from the Lake 

 of the Woods in an cast-southeast direction obliquely across the granitic 

 areas we find that they become proportionately narrower and longer in 



