CIIAI'TKR. I. 



T'M'iniR \\>\\\ . 



Till-; le-jion here un.hr consideration lies mostly between 

 tin- 4.")tli ;m<l 4!th parallds of north latitude. Its width 

 fn>m rmrtli to south is '27(5 miles, and. measured west 

 from the 1<>4th meridian it extends 624 miles across the main 

 and secondary rank's ,.f the l\o< ky Mountains. The t-ital area 

 is tins.- to 17."). (Kin s(|iiare miles. This embraces nearly all of 

 tin- State >f .Montana and includes a portion of eastern and 

 northern Idaho. 



Tin- mountain ranires of Montana have mostly a southeast 

 to northwest direction. They are thus essentially parallel with 

 valleys ..!' <jnat<T ..r |. ss width between. Most of these inter- 

 moiintain valleys have in width from two to twenty miles of 

 river bottom and bench land, mostly the latter, which ascends 

 'gradually or abruptly into foothills, behind which rise ruined 

 mountains, dissected by numerous strong tributaries of the main 

 stream^. Th valleys proper are but narrow strips as a rule in 

 the broad drainage basins of which they form a part. 



The mountains and valleys have been formed by successive 



faultiii-_r and tiltinir on a "rand scale. The eastern slope of a 



rari'je usually represents its fault face (7), the western slope 



inclines mop- -jradually to the foot of the next abrupt ascent. 



Only two _'!'' at mountain chains, however, figure conspicuously 



the spread of tin- flora of the state, the others are 



.bordinate or iie'jli'jible importance. One of these is 



the r.in.-r L'oot Mountains and those shorter ranges to the north- 



Hine -j'-ii'-ral al i'jiiment, the other is the ( 'out 'mental 



Divide, 

 Th.- eastern border of Montana <>n the Missouri lies 1898 feet 



above sea level. Knun this point the land irradually rises to 

 '"' miles to the \v,-st and drops down a<rain to about 

 1800 feet when- the Kn.,tenai li'ivei' crosses the westei'n boundary 

 of M'.ntana. the lowest point in the State. The altitu le of half 

 the > more ^ ab<,\e :',nno feet, The hirhest point is 



