90 GEORGE MERCER DAWSON ON THE 



with comparatively narrow intervening valleys. Nearly parallel to 

 these two great ranges is the Coast or Cascade range, in which the 

 average altitude of the higher peaks is between 6000 and 7000 feet, 

 while some exceed 9000 feet. A fonrth range may be traced, in a 

 partly submerged condition, in the mountains of Vancouver and the 

 Queen-Charlotte Islands. Between the Coast range and the Selkirk 

 or Gold range lies the great interior plateau of British Columbia, 

 with an average width of 100 miles, and a mean elevation of about 

 3500 feet. Its height, on the whole, increases to the south, while 

 northward it falls gradually towards the cluster of great lakes, and 

 the low country of the Peace-River valley. This plateau region has 

 over a great part of its area been covered by wide-spread flows of 

 basalt and other igneous rocks, in the later Tertiary period. It is 

 now dissected by deep and trough-like river-valleys, into most of 

 which water standing at 3000 feet above the present sea-level would 

 penetrate, dividing its surface into a number of islands. In some 

 places the plateau is pretty level and uniform ; but usually it is only 

 when broadly viewed that its character is apparent. The best pub- 

 lished maps of British Columbia but imperfectly indicate even its 

 grander physical features ; but I believe, from information received, 

 that the north-western end of the plateau is blocked by high moun- 

 tainous country, formed by a coalescence of the three great ranges 

 in latitude 55° 30'*. Nearly coincident with the 49th parallel is a 

 second transverse mountainous zone, formed in a similar way, which 

 may be considered as bounding the plateau to the south, though tra- 

 versed by several great river-valleys, of which that of the Okanagan, 

 in longitude 119° 30', is the deepest. 



No modern glaciers have been seen in the Rocky Mountains, near 

 the 49th parallel, though much snow lies among the higher peaks, 

 and northward, about the sources of the Saskatchewan, true glaciers 

 are found. It is probable that some glaciers may also exist in parts 

 of the Selkirk range. In the Coast range glaciers abound from the 

 49th parallel north-westward. To the south they are summit- 

 glaciers, but northward, about latitude 51°, fill long valleys, and still 

 further north are reported as comiug down nearly to the sea-level in 

 some places. 



Three main structure-directions serve to account for the greater part 

 of the depressions of the surface now occupied by rivers, lakes, and 

 the fjords of the coast: — 1, a north-westerly and south-easterly series 

 of hollows, dependent on the general direction of folding of the rocks 

 of the country ; 2, a north and south, or meridional series, due, where 

 I have had the opportunity of examining it, to systems of parallel 

 cracking ; 3, an east and west, or transverse series, occupied by many 

 lakes and rivers, but the cause of which has not yet been determined. 

 There are also traces, indicated by valleys in some parts of the map, of 

 structure transverse to the main direction of folding. It is, of course, 

 not intended to affirm that the causes mentioned produced these 

 features directly, but merely that certain structural lines of weakness 



* Called the Peak Mountains on old maps. 



