322 GEOLOGY OF THE BLACK HILLS. 



The tall slender pines will be very useful to the settlers in this region, 

 being well adapted for fencing and house-building purposes. The resinous 

 character of the wood makes it a most excellent fuel, burning with a long 

 smoky flame, giving out an intense heat, almost equaling in this respect 

 the pitch-pine of the Southern States. 



On the tops of the ridges and hills, where the trees are exposed to the 

 violence of the storms, the timber is wind-shaken and injured in quality ; 

 but on the more sheltered hill-sides, the broad level mesas, and in the 

 numerous valleys and parks, the trees are free from this evil, and are remark- 

 ably straight and regular in growth. Pines were sometimes encountered, 

 blown down by the wind across the narrow ravines, the trunk of the tree, 

 even when 1 to 2 feet in diameter, being broken short off by the violence 

 of the fall on the rocks. This rarely happens with the spruce under similar 

 circumstances, owing to the greater transverse strength of the wood. 



The Black Hills have been subjected in the past to extensive forest- 

 fires, which have destroyed the timber over considerable areas. Around 

 Custer Peak and along the limestone divide, in the central portion of the 

 Hills, on the headwaters of the Box Elder and Rapid Creeks, scarcely a 

 living tree is to be seen for miles. The timber, deadened by the fire and 

 the trees left standing, their decaying trunks stripped of bark by weather 

 or prostrated by the wind, cover the ground, crossing each other at all 

 angles, forming an impassable abattis. 



Some portions of the parks and valleys, now destitute of trees, show 

 by the presence of charred and decaying stumps that they were once 

 covered by forest, but generally the pine springs up again as soon as it is 

 burnt off, though sometimes it is succeeded for a time by thickets of small 

 aspens. 



Along the eastern and northeastern slopes of the Black Hills, at a 

 distance of not more than ten miles from the edge of the plains, the pine is 

 partly replaced by burr-oak and white elm of moderate size. These trees 

 are found in groves in the valleys and swales between the hills, and 

 associated with white birch in the ravines of the streams. Neither the oak 

 nor elm attains a large size, the trees averaging 30 to 40 feet in height and 

 10 to 15 inches through. 



