144 AN AMERICAN FOREST BLOWN DOWN. 



moved with great velocity along the desert. The 

 dust clouds in spots rose to a great altitude, and as they 

 progressed occasional blasts of wind shot out laterally 

 across the water, showing how fiercely the storm was then 

 blowing on shore. This lasted perhaps an hour, and 

 then all was again still ; the ruddy coloured chain of 

 desert hills once more stood out in all their barren 

 desolation; their outlines in the now pellucid atmo- 

 sphere showing as clearly as if they were modelled in 

 adamant, so that their minutest details were dis- 

 cernible. 



In the same way in the wooded tracts of forest, 

 found near the courses of rivers in the great plains 

 region of America, the track of some of these rushes 

 of air may be traced, where they have passed through 

 the wood, like the blast from the mouth of a cannon. 

 In their course (which may vary from 100, to per- 

 haps 500 or more yards in width), the whole forest 

 is levelled to the ground; not one tree, in many cases, 

 having been left standing where the vortex of the 

 storm has passed. The narrow front along which 

 such hurricanes frequently move, is thus seen in 

 the clearest way; and the traveller through these 

 wild regions (as they were when we visited them) 

 had frequent and ample opportunity of noting their 

 exact effects. At other times circling eddies of wind 

 will scoop a space, right out of the heart of a wood, 

 destroying everything within its vortex, but leaving 

 the trees all round it untouched; it is therefore clear 

 that the whirlwind has been of the ascending form : 

 and so everything outside of its rotatory whirl escapes. 

 The influence of the eddy in fact probably extends 

 only a very short way beyond its edge. We do not 



