30 THE PLAINS. 



posed to account for the treelessness of the plains, have 

 really comparatively little to do with it. On the high 

 prairie the grass is very short. When on fire, the blaze, 

 from six to fifteen inches high, moves over the ground 

 slower or faster, according to the wind, but not with vitality 

 or heat enough to seriously injure a bush of a few inches 

 in diameter. Yet the high prairie is bare. In the 

 canons the grass is often five to ten feet high, and dried 

 leaves, shrubs, bushes, vines, furnish a storehouse of fuel, 

 sufficient to make a roaring vortex of twenty feet of 

 flame. And yet the canons are full of vegetation. The 

 only occasion where fire acts a prominent part as a cause 

 of the treelessness is at the lower ends of the canons, 

 where the bottoms widen out, and the hills, becoming 

 lower, are more remote, and afford less protection from the 

 wind. Trees will grow in such positions, but not so 

 stubbornly as in the canons. The fire in the long grass 

 about their trunks, fanned by the winds to which they 

 are exposed, will destroy the smaller, and so burn the 

 trunks and branches of the larger trees as frequently to 

 kill them. In many such places the islands in the stream 

 which fire cannot reach will be covered with fine trees 

 and thick vegetation, while the contiguous banks are as 

 bare as any portion of the high prairie. On many 

 streams, particularly on the North Platte, some of the 

 narrow bottoms of the canons are covered with splendid 

 trees, large and old, without any small young trees, or a 

 particle of underbush. This is undoubtedly the effect of 

 fire, and proves, I think, that prairie fires were not so 

 frequent a hundred years ago as now. 



As the settlements creep up the stream, and care is 

 taken to prevent fires, the young trees spring up, and, as 

 the growth of the cotton- wood is extremely rapid, all the 

 ground suited to their propagation is soon covered. 



Another great enemy to the trees is the beaver. This 

 animal is very plentiful on all the streams where there is 

 sufficient vegetation for his sustenance. The wooded 



