BRITISH COLUMBIA AND ADJACENT REGIONS, 



277 



from the axis of these rocks to the east or north-east were first ob- 

 served, and appear in abundance, at a height of from 2300 to 2500 

 feet, near the D'Echafaud River, in latitude 55° 45', longitude 120°. 



East of this point tho wide Peace-Biver plateau extends, and the 

 general character of the county in regard to its superficial deposits 

 is so uniform that it is unnecessary to particularize localities in de- 

 scribing it. Its surface is so thickly covered that exposures of the 

 underlying rocks are, as a rule, found only in the larger river-valleys. 

 The lower layers of the drift appear to represent the Boulder-clay of 

 the great plains to the south and east and the northern part of British 

 Columbia to the west ; they are sandy clays with boulders and 

 stones in abundance, and their upper surface is somewhat irregular, 

 rising in some places in ridges or broad gentle elevations, which 

 stand out above the newer silty deposits in which a great part of 

 the surface is enveloped. The silt is generally pale grey or fawn- 

 colour, and while in places passing almost into clay, becomes occa- 

 sionally a fine sand. This sandy covering of the surface is found 

 especially at the southern rim of the Peace basin, near the Atha- 

 basca, where the plateau attains an elevation of about 3300 feet 

 (long. 117°). The ridges at this elevation are still thickly strewn 

 with Laurentian boulders. 



In regard to the material of the drift, the stones and boulders 

 scattered over this great district are, in part, those of the Pocky Moun- 

 tains to the west, in part derived from the Laurentian axis to the 

 north and east. The fragments from the first-mentioned source are 

 generally of quartzite ; the limestone and other softer rocks accom- 

 panying these in abundance in the vicinity of the mountains, de- 

 creasing rapidly as we recede from them. The Laurentian mate- 

 rial is chiefly gneiss and granite of the usual well-marked types. 

 Between the Athabasca and Saskatchewan (long. 113° 30') the 

 plateau attains a maximum elevation of about 2300 feet, and 

 Laurentian boulders are everywhere exceedingly numerous. 



Additional Notes on the Coast. 



In the fiords penetrating the coast of the mainland of British 

 Columbia, and channels intervening between the numerous islands 

 lying off it, from the southern extremity of Alaska to the north end 

 of Yancouver Island, marks of the passage of glacier-ice are to be 

 found wherever the rocks are unweathered (see Map, ]). 278). These 

 marks are generally in strict conformity with the directions of the 

 passages, which it is evident must have been filled with ice moving 

 in the main seaward from the coast-ranges, in which many smaller 

 glaciers are still found. Whether at any time the supply of ice has 

 been so great as to form a confluent mass flowing toward the sea, at 

 right angles to the general direction of the coast mountains, and with- 

 out regard to the smaller features of the surface, has not been definitely 

 ascertained ; but it is highly probable that this has happened. The 

 outer islands of the Shore archipelago have scarcely been examined ; 

 but the little group called the Gnarled Islands (lat. 54° 39'), on the 

 south side of the strait, thirteen miles wide, which lies between 



Q.J.G.S. No. 146. u 



