st. johx.] jackson's basin. 443 



pliitkeatres and profound gorges that mark the crest of the WindEiver 

 Mountains, and the scarcely less remarkable or inferior volcanic heights 

 in the vicinity of To-gwo-tee Pass and the region around the sources of 

 the Yellowstone. 



JACKSON'S BASIN. 



Before passing to the consideration of the highlands of this portion of 

 the district, which will be treated of in specific connected order, a brief 

 notice of the mountain-locked valley commonly known as Jackson's Hole, 

 will first engage our attention. Extending in a northerly and southerly 

 direction a distance of about 45 miles, ranging in breadth from 5 to 15 

 miles, and in altitude 6,000 to 6,800 feet above sea-level, it presents a 

 surface diversified by levels of low, gravelly bottom, beautiful terrace- 

 plains, with low, grassy hills rising in the midst, and densely timbered 

 ridges skirting the western border, along which are nestled the lakelet 

 expansions of the streams that issue from the Teton Mountains, and to 

 the north the beautiful body of water into which the Snake Eiver ex- 

 pands, which has received the name of Jackson's Lake. To the west 

 rises the lofty, precipitous barrier of the Teton Range, which to the north 

 sinks to the level of the high outlying volcanic divide at the northern 

 extremity of the range, and to the south is prolonged in the mazes of 

 the Snake River Range, forming a continuous belt of rugged mountain 

 wall abruptly hemming this side of the valley. On the east the moun- 

 tain border is much less regular and elevated, with a wide belt of out- 

 lying, gentle slopes, interspersed with forests of pine, groves of aspen, 

 and extensive tracts of pasturage. Perhaps no region in the Northwest 

 presents so varied, beautiful, and majestic scenery. 



Quaternary. — The whole valley is filled with an immense accumulation 

 of Quaternary deposits, consisting of well- water- worn or rounded debris 

 derived from the neighboring mountains, and which the action of the 

 streams has formed into various terrace-levels, the higher of which form 

 quite extensive plains covered with sage and excellent grazing. The soil 

 is of a light -brown marly nature, based upon a subsoil of coarser materials ; 

 which latter often appears at the surface in the lower bottoms, and also 

 in the higher levels, giving rise to gravelly, barren tracts. Again, con- 

 siderable areas of the bottoms along the beaver-dammed water-courses 

 are converted into ponds and willowy bogs, which merge into luxuriant, 

 spongy meadows, very like the natural vegas of the Southwest. The 

 streams are generally rapid and shallow, their clear, cold waters spread- 

 ing over bowlder-strewn beds and interrupted by bars of shingle and 

 cobblestones, which often divide the streams into a network of easily- 

 forded channels ; but in the season when their volume is swollen by the 

 melting of the snow and their banks run full, they present far more 

 formidable obstacles to the progress of the traveller. 



In the debouchure of East Pass Creek the west-side terraces may 

 be well studied. They are seen to form high undulating and sloping- 

 benches, for the most part heavily timbered with impenetrable tracts of 

 young pines, and strewn with large blocks of granite. In their passage 

 across this bench the small streams have eroded pretty little valleys 40 

 to 60 feet deep, and have also built lesser terraces, which are conspicu- 

 ous for the prevalence of water- worn fragments of sedimentary rocks, sand- 

 stone and limestone, which the streams brought down at a later period. 

 To the north, however, it is very likely that Archaean debris prevails 

 throughout, in the ancient as well as in the more recent formed benches. 

 Professor Bradley and Mr. Taggart, who examined in this quarter the^ 

 outlying benches immediately at the foot of the culminating Archaean 



