250 GEOLOGICAL SUEVEY OF THE TEEEITOEIES. 



other Territories we find the difference much greater than would be an- 

 ticipated. For this purpose I give here the elevations of a few points : 



Feet. 



Albuquerque, New Mexico 5, 032 



Santa Fe, New Mexico. . 6, 840 



Denver, Colorado 5, 300 



Green Eiver, at the railroad (grossing 6, 140 



Salt Lake Citv 4, 350 



The Humboldt Sink 4, 017 



Fort Laramie 4, 519 



Sweet Water Eiver, at Independence Eock 5, 998 



South Pass City 7, 857 



Fort Hull, (about) 4, 200 



From this we see that even thelowest point of the Great Basin, near 

 the "Humboldt Sink," is 1,120 feet above the mouth of the St. Eegis de 

 Borgia and 733 feet above Fort Owen. This very important fact in 

 regard to the physical geography of this Territory will serve as an ex- 

 planation of its comparatively mild climate, notwithstanding its north- 

 ern latitude. 



The entire Territory may be divided into four sections, each having 

 its water system and natural boundaries tolerably well defined, as fol- 

 lows : The northwestern, which includes all that portion lying between 

 the Eocky Mountain and Bitter-Eoot Eange ; the southern, which is 

 drained by the three forks of the Missouri; the southeastern, which is 

 drained by the Yellowstone •, and the northern, which includes the val- 

 leys of Milk and Missouri Elvers, and the bordering plains. Mr. Gran- 

 ville Staart designates a fifth basin, embracing the country drained by the 

 Boulders and. the lower portion of the Jefferson ; but for the present 

 purpose, the foregoing division is probably the best, his fifth basin being 

 considered as a portion of the southern section. 



THE NOETHWESTEEN SECTION. 



This section, as before stated, is situated between the Eocky Mount- 

 ain Eange on the east and the Bitter-Eoot and Coeur d'Alene Mount- 

 ains on the west, extending from the forty-sixth parallel of latitude to 

 the British possessions, and including all of Missoula Oounty and the 

 southern half of Deer Lodge County. It is about one hundred and fifty 

 miles wide and two hundred miles long, containing an area of thirty 

 thousand square miles ; and is traversed from southeast to northwest 

 by Clark's Fork of the Columbia, and its leading tributaries. 



The northern part is variable in character, having some open prairie 

 country and valleys of limited extent, while much of it is broken and 

 rugged and covered with heavy pine forests. It is drained by Flathead 

 Eiver, which has three leading tributaries— Maple Eiver, coming from 

 the northwest ; Flathead, from the north ; and another branch from the 

 northeast. Near the forty-eighth j^arallel this stream expands into a 

 beautiful lake about thirty miles long and ten or twelve miles wide. 

 Below this it is of considerable size, flows in a southwest direction for 

 about fifty miles, and joins the Missoula, the two forming Clark's Fork.* 



* The main brancli of this stream has a number of different names. From the junc- 

 tion of Deer Lodge and Little Blackfoot Eivers to the mouth of Big Blackfoot, it is 

 called Hell Gate Eiver ; from there to the mouth of the Flathead it is called Missoula, 

 from there it retains the original name of Clark's Fork, though it is sometimes called 

 Columbia.. 



