CHAPTER II. 



SOUTHWESTEKN SECTION. 



GENEEAIi TOPOGEAPHICAIi FEATUKES, DRAINAGE, ETC. 



The soutliern boundary of tlie district, conforming to the parallel 43° 

 north latitude, forms tlie base of an irregularly triangular-sbaped area, 

 the remaining two sides of wbicb are defined by the Snake Eiver, and 

 comprising in the neighborhood of 1,900 squaxe miles, embraces the 

 territory referred to under the above designation. Of this area quite 

 two-thirds are embraced in the highland region which stretches across 

 the southern line from the western boundary of the district to Salt 

 Eiver, its northern border sinking into the Snake plains, which latter 

 comprise the remaining third of the section. The Snake Eiver bound- 

 ary, of course, constitutes the main drainage, receiving the numerous 

 affluents which drain the interior southern highlands. Of these, the 

 Blackfopt Eiver, whose course is mainly within this Territory, is the 

 largest. It rises in the central southern portion in a broad basin lying 

 to the north of the Bear Eiver drainage, and flowing southerly, it re- 

 turns ; passing thence northerly a distance of about 25 miles it again 

 suddenly bends westward, breaking through the upraised border of the 

 volcanic flows and emerging into the plain, joins the Snake a few miles 

 north of the southwest corner of the district. It is a fine httle stream 

 with a total length of 75 miles or so, with a diversified course of interior 

 grassy, sage plain or basin, basaltic caSon, and open sandy plain. In 

 the extreme southwest the sources of Eoss Fork flow down from the 

 Mount Putnam Hills, and gathering on the edge of the x)lain, flow west- 

 ward beyond our limits into the Snake. In the northerly continuation 

 of the same basin in which the Blackfoot rises, several other small 

 streams gather their waters from sj^rings which issue from the volcanic 

 ledges and neighboring highlands, and flow northward through Willow 

 Creek into the upland plain where their courses are caiioned in basaltic 

 rocks. Still farther to the east the drainage of a considerable area is 

 accumulated in the marshy depression known as John Gray's Lake, which 

 finds an outlet also through "Willow Creek into the Snake to the north- 

 westward, its lower course being canoned in the basalt of the border 

 upland. The eastern border is drained by several smaller streams, 

 among which McCoy and Fall Creeks are the largest, which take their 

 rise in the heart of the Caribou Eange in beautiful little mountain 

 basins, forcing their way across the axis of the range through deep, 

 picturesque gorges. In the southeast. Salt Eiver gains the Snake at a 

 point just below the lower entrance of the Grand Canon. It winds 

 through a broad valley flanked by hills, which, farther to the south wai'd 

 beyond our district, opens out into an extensive basin-like area. 



The eastern border of the region is occupied by a wide belt of low 

 mountains, the Caribou Eange, which trends northwest and southeast, 

 with an extent of some 40 miles within this district. Separating the Car- 

 ibou from the Blackfoot Eange, on the west intervenes an extensive 

 basin drained by Willow Creek, the average breadth of which is about 

 12 miles, and which is traversed by several low, rocky ridges, whoso 



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