GEOLOGICAL SURVEY OF THE TERRITORIES. 209 



then, the latter stream has, during the spring, carried more or less 

 water, which, however, has all sunk into the sauds of the lower part of 

 the channel before reaching Blackfoot, to which it should naturally be 

 tributary, if we may judge by the shape of the country as seen from 

 Higbam's Peak. Indeed, from that point, certain water-courses were 

 seen which lead me to suspect that, after once sinking, it again escapes 

 from the sand and renews its individuality, at least for a short space. 

 At present, it is evident that the connecting channel has been so deeply 

 cut that Sand Creek carrifesfar more water than does the original chan- 

 nel of Willow Creek below the separation ; and, if this continues to be 

 the case, it is not improbable that it may succeed in clearing away the 

 sand-obstructions from its lower channel and in establishing complete 

 surface-connection with Blackfoot. The tracing of these old channels — 

 and of others which doubtless exist in this broad flat i)lain — and the de- 

 termination of the relative dates of their occupation will be of much 

 local interest to geologists who may, in the future, make their homes 

 hereabout. On the upper course of Sand Creek, later in the season, we 

 found many shells in the soil of the banks, giving further proof of the 

 lateral movements of the old channels, while yet the general course of 

 the drainage was unchanged. 



Crossing Snake Eiver at Taylor's or Eagle Eock Bridge, we encamped 

 on its west bank, abotit seven miles above. The stream was very full, 

 carrying an immense body of water, whose surface was constantly broken 

 b}' the eddying whirls characteristic of irregular bottoms. After a long, 

 hot day, the temperature of the stream, at 6.20 p. m., was 62°, the air 

 being at 78°. At 4,20, on the next morning, with the air at 47°, (the 

 minimum thermometer marking 44°,) the river was still at 62°. Only a 

 very large and much-disturbed flow of water could thus escape all effects 

 of so great an atmospheric change of temperature. 



At medium and low stages of water, the river is confined, at the 

 bridge, to a single narrow and deep channel, worn in the basalt ; but, in. 

 times of flood, it here occupies two bridged channels, and elsewhere 

 spreads considerably upon its banks. On either side there are old 

 channels, more or less plainly marked, which were occupied by the 

 stream at times before it had worn its present channel so deep into the 

 rock. In xiassing northward, we found many of these, mostly dry, 

 though some of them are occupied, during the rainy season, by the 

 drainage of the neighboring plain pud retain some pools through most 

 of the year. The road here follows the bottoms, without anywhere 

 rising to the level of the surrounding plain. 



On the morning of July 16, we left the stage-road at Market Lake 

 Station, and turned eastward toward the Tetons, whose highest peak had 

 been visible at intervals, just above tiie horizon, ever since we crossed 

 the river. The basalt-terrace, which here stands from 50 to 60 feet above 

 the stream, is much broken near its borders, the edge being more or less 

 undermined and sunken. At short distances within the borders are 

 many depressed areas, occupying a few acres each, whose walls appear 

 to have once inclosed small ponds ; but these have long since beett 

 drained through the underlying sand and gravel, when the river cut its 

 channel to this lower level. Here, again, we see many of the unbroken 

 knolls of basalt, evidently consequent upon the shape of the underlying 

 surface at the time of the overflow. 



Since leaving Sand Creek, we had had constantly in view two rounded 

 buttes of moderate elevation, which were now immediately in front of us. 

 ^Vs we ai)proached, we found that they stood in the lower angle between 

 14 G s 



