130 C. W. Hayes — Expedition through the Yukon District. 



contours are generally smooth and flowing, and the surface, 

 excei3t in the southern and glaciated portion of the region, shows 

 the effect of long continued exposure to the action of subaerial 

 "agencies. While rock decay has made little progress, so that 

 the surface is practically free from soil, rock disintegration has 

 been extremely active and the country is thickly mantled with 

 rock debris of varjdng degrees of coarseness. Projecting through 

 this mantle of debris, above smooth gentle slopes, are many 

 isolated pinnacles and toAvers of rock rendered esj)ecially con- 

 spicuous hy contrast with their moss-covered talus slopes. Sur- 

 face degradation is greatly retarded by the luxuriant growth of 

 moss which covers practically the entire surface of the country. 

 The annual precipitation is largely confined to the winter months, 

 and the water from the melting snow is held by the sponge-like 

 moss, which remains saturated throughout the short but hot and 

 dry summer. Thus, Avith a rainfall which in loAver latitudes 

 Avould condition an arid region, a large part of the surface is 

 SAvampy, quite irrespective of slope ; that is, Avherever the ma- 

 terial composing it is sufficiently compact to become impervious 

 to Avater by freezing. On account of this slow and imperfect 

 surface drainage the slopes are not cut into the ravines and 

 arroyas so characteristic of arid regions. The plateau extends 

 Avest of White river, though it is there rather more diversified 

 than toward the east by a number of high sharjo peaks, probably 

 of A'olcanic origin. 



Approaching the northern base of the St Elias range the 

 plateau character is almost Avholly lost, giving Ava}^ to steep and 

 rugged though not lofty mountains separated by rather wide 

 river valleys. There is, however, no merging of the plateau in 

 the St Elias mountains, but south of a Avell marked limit the 

 AAdiole character of the topography suffers a complete change. 

 BetAveen the southern limit of the interior plateau and the 

 northern base of the St Elias mountains is a depression running ,, 

 23arallel Avith the mountain range and having an altitude of 

 about 4,000 feet. It contains the upper part of White river for 

 a distance of about thirty miles, and probably also in its north- 

 Avestern continuation the headAvaters of the Tananah. South- 

 Avard across this de]3ression Avas seen the abrupt northern face 

 of the St Elias mountains, Avith many sharp and rugged peaks 

 rising to altitudes of 10,000 to 12,000 feet. Only the steepest 

 slopes Avere free from snoAV, and the region presented a striking 



