PHYSIOGRAPHY OF THE BOSTON MOUNTAINS, 

 ARKANSAS ^ 



The highlands of Arkansas lie in the northwestern part of 

 the state, and comprise about half its area. They are divided, 

 physiographically, into a north and a south part by the valley 

 of the Arkansas River. They are also divided structurally into 

 the same parts, the former being a region of horizontally-bedded 

 rocks, somewhat disturbed by faulting and folding, while the 

 latter, known as the Ouachita Mountains, is distinctly a folded 

 region. 



This northern division of the Arkansas highlands, with its 

 westward extension into Indian Territory, constitutes the south- 

 ern part of the Ozark region.^ In Arkansas, it is divided into a 

 low and a high part, the former extending northward into Mis- 

 souri, and passing, along its southern border, into the latter, by 

 an irregular but bold escarpment from 500 to 1000 feet high. 



It is this latter region that is known in Arkansas as the 

 Boston Mountains. Including that part which lies in Indian 

 Territory, its total length is about 215 miles, about 170 of which 

 is in Arkansas. Its average width approximates 35 miles. On 

 the south, it passes into the valley of the Arkansas River by 

 steep slopes, though less precipitous than those on the north. 



These mountains are by far the highest part of the Ozark 

 region as well as the most picturesque. Their highest point, so 

 far as determined, is some miles east of the town of Winslow, 

 on the St. Louis and San Francisco railway, where the altitude 

 is 2,250 feet. 3 From this region of highest elevation, they 



' Read before Section E of the American Association for tlie Advancement of 

 Science at the Denver meeting, August 1901. 



^ Tlie Ouachita Mountains have been included by some writers witli the Ozarks ; 

 but because of the great structural and topographic differences in the two regions, to 

 say nothing of the probable historic differences, this is manifestly wrong. 



3 Topographic map United States Geological Survey, Winslow quadrangle. 



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