GEOLOGICAL WORK OF THE ATMOSPHERE 91 



conclusion, has however, been questioned. The loess of some 

 other regions has been referred to the same origin, and much of it 

 is quite certainly eolian. 1 From the flood plains of such rivers as 

 the Missouri, clouds of dust are swept up and out over the adjacent 

 high lands at the present time, whenever the surface of the flood 

 plain is dry and the wind strong. This dust is very like loess, if, 

 indeed, it is not loess. 



Fig. 53. Interstratified eolian sand and loess near Milford, Nebraska. 



(Condra.) 



The transportation of dust is important wherever strong winds 

 blow over dry surfaces free or nearly free of vegetation, and com- 

 posed of earthy or sandy matter. Its effects may be seen in such 

 regions as the sage-brush plains of western North America. The 

 roots of the sage-brush hold the soil immediately about them, 

 but between the clumps of brush where there is little other vege- 

 tation, the wind has often blown away the soil to such an extent 

 that the base of each shrub stands up several inches, or even a 

 foot or two, above its surroundings. Such mounds are often partly 

 due to the lodgment of dust about the bushes. 



^hamberlin; Jour, of Geol., Vol. V, p. 79. 



