256 GEOLOGICAL SURVEY OF THE TERRITORIES. 



Eiver, stiinds a large coDical mound, about 65 or 70 feet high aud j^er- 

 haps 250 feet in diameter at the base. Though circumstances prevented 

 me from making the desired examination of it, yet, from the regularity 

 of its outline, 1 feel quite certain that it is a structure of the age of the 

 Mound-builders. No other relics of that interesting people were seen 

 upon the entire trip, unless the rude rock-wall reported by Mr. Steven- 

 son as existing upon the summit of Mount Haydeu should prove to be 

 such. 



The broad valley soon narrows again to a deep caiion, walled by red 

 shaly sandstones, containing uo fossils beyond indistinct fucoidal mark- 

 ings, which are referred with doubt to the Triassic i)eriod. The gray 

 beds of the lower part of the series make their appearance in the lower 

 end of the canon. The stream is here broad aud shallow and easily 

 forded, so that the canon can be easily traversed at this season. From 

 this point the valley is wide and terraced, the bordering ridges being a 

 mile or more apart ; and this continues, gradually widening, to the 

 basin of Jackson's Lake. Just at the mouth of the narrow caiion, the 

 river bends sharply to the right and then to the left, so that the form 

 of the slopes gives the descending traveler reason to expect here a large 

 affluent ; but none exists. About a mile lower, we came suddenly upon 

 a small basin of hot springs, most of which are now nearly extinct, 

 though some large mounds on the river-bank give evidence of great 

 activity in former times. The active vents seen were all in the bed or 

 on the bottoms of the river, so that their flow was more or less mingled 

 with river-water ; and no temperatures were taken. The deposits are 

 siliceous. Mr. Taggart found, near here, at the foot of the second ter- 

 race, several conical depressions, from 30 to 40 feet deep and from 75 to 

 100 feet in diameter, which might have been old spring-basins, though 

 their origin is by no means certain. At the bottom of one of these lay 

 two dead rabbits, upon which there were no signs of violence. No other 

 signs of escaping gas were noticed. 



This hot-spring basin occurs at the upper edge of a belt of basalt, 

 which forms, a little farther on, lofty vertical walls, from 300 to 500 feet 

 high, through which a small stream, coming in from the north, has worn 

 a deep, narrow cauon. About two miles below this, high walls of nearly 

 white limestone appear on either hand, though the fading light of even- 

 ing prevented a clear understanding of the relative position of the beds 

 at the junction. It is probable that the basalt, escaping from some vent 

 in the volcanic range of Red Mountain, filled a large north and south val- 

 ley, of which the limestone had previously formed the western wall; "and 

 semi-metamorphism should be found in the limestones near the line of 

 contact. 



About three miles more brought us to the camp of the main X)aTty, at 

 the mouth of Lake Fork, where the broad valley of the Snake makes a 

 sweeping curve into its future southerly course, while Lake Fork itself 

 joins it from the north through the narrow caiion which it has worn 

 down through a high barrier of volcanic rock. 



In descending from Lake Lewis, the main party found the river-banks 

 low and rocky for a short distance, before the stream enters a caiion with 

 walls from 150 to 200 feet high, in which were encountered sharp rapids 

 and a vertical fall of about 30 feet. Then, for a mile or two, the slopes 

 are gradual, with narrow, swampy bottoms along the river. About three 

 miles below the lake, high, rocky banks indicate the approach to a deep 

 canon, which really commences at about three .and a half miles, with 

 perpendicular walls on both sides, inclosing a narrow channel with a 

 rapidly-sloping rocky floor, in some places partially obstructed by huge 



