GEOLOGICAL SURVEY OF THE TERRITOEIES. 253 



queiitly au inch or more in diameter. At the very crest, vegetation is 

 reduced to a few grasses and Alpine plants, and the gray, red, and yel- 

 low rock-lichens which so commonly make tbese high levels brilliant. 



The extreme crest consists of a dark, brecciated porphyry ; but, only 

 a few feet lower, we find an abundance of the purplish-pink laminated 

 porphyry, which forms a large part of the mountain. All the rock is 

 quite ferruginous, so that, on weathering, it attains the dark-red tint so 

 characteristic of the mountain as seen from a distance. 



In the south slope of the mountain there is another huge crater like 

 hollow, but I doubt its being really an old crater. Its slo[)es are steep, 

 with loose rubbish, on which we could hardl3" stand, while at the same 

 time we could with difficulty drag our horses down it to our chosen 

 camping-spot in a grassy opening by the side/)f the small stream formed 

 from the snow-banks, which probably never entirely disappear from the 

 head of this hollow. A snow-fed pond lies on a small flat near the head 

 of the stream. A large dike of very compact trap crosses this ravine 

 just above camp, running about north 44° west. Mr. Ilering, with his 

 assistants, remained upon the summit until ^fter dark, for star-observa- 

 tions, but succeeded in bringing his instruments safely to camp. 



Next morning (12th) Mr. Heriug and Mr. Stevenson returned to the 

 main party, while the rest of us went on to examine the head-waters of 

 the Snake, whose general position we had seen from the summit of the 

 mountain. About a mile below our camp, we came to a curious little 

 spring-pool, standing on a marshy bottom. Around its edge there was 

 a dam-like border of roots, grass, and moss, by which the water was 

 held at perhaps a foot above the surrounding marsh. Apparently the 

 spring had burst up through an old turf, which had turned up at the 

 edges, and through which the water had never been able to break down 

 au open passage, though escaping through its mass and over its edges. 



Our descent continued to be quite rapid for nearly two miles farther, 

 when we reached the meadow-lilvc bottom of a stream coming in from 

 the left, which apparently giithers the water from the springs which 

 escape from the foot of the mountain, nearly round to the basin of Heart 

 Lake. From the junction of the two streams we held our course south- 

 easterly, over a spflr about 500 feet high, until we struck Heart Kiver 

 not far above its junction with Barlow's Eiver. As the streaia leaves 

 Heart Lake, it flows for some miles through dense forests of pine and 

 spruce, and then through a deep, narrow canon, apparently of volcanic 

 rock, from which it issues just above where we struck it. This river is 

 evidently not subject to the great freshets which are common on many 

 of the streams hereabout, and it is therefore probable that Heart Lake 

 acts as a retaining reservoir for the waters of the melting* snows, while 

 the melting itself goes on more slowly in this densely-timbered basin 

 than on the barer slopes. 



The valley about the junction of the two streams contains a consider- 

 able area of beaver-ponds. Continuing southward, up, the valley of Bar- 

 low's lliver, we rode for two or three miles over a level, sage-covered 

 prairie, but little above high-water mark. The stream has a very wide, 

 gravelly channel, in contrast with which its present flow seemed very 

 small, though really of pretty good size. The lower slopes of Mount 

 Hancock on the west, and those of an unnamed peak of nearly equal 

 height on the east, soon close in upon the stream, forming a deep and 

 narrow caiion. To avoid traveling in the bed of the stream, we followed 

 some of the numerous gauie-trails, which led us to from 300 to 400 feet 

 above its level, but finally brought us down again about ten miles from 

 Heart Eiver, and just below some small falls and rapids, where the 



