THE LOESS 409 



ing for an untold period. As applicable to China, Kicht- 

 hofen's theory is perhaps adequate. Mr. Pumpelly is also 

 inclined to accept the theory as applicable to America, re- 

 marking that — 



No one can realize the capacity of wind as a transporter of 

 fine material who has not lived through at least one great storm 

 on a desert. In such a simoon the atmosphere is filled with a 

 driving mass of dust and sand which hides the country under 

 a mantle of impenetrable darkness, and penetrates every fabric : 

 it often destroys life by suffocation, and leaves in places a deposit 

 several feet deep. 



The prevailing westerly wind, carrying sand, carves and pol- 

 ishes the rocky crest of the Sierra Nevada, and, as Mr. King 

 tells me, has formed long wind-stream deltas — if I may coin 

 the term — in the form of lofty sand ranges stretching from 

 each pass eastward, far out on the desert. 



The often cited instances of far-driven volcanic ashes show 

 the ability of the wind to carry comparatively coarse dust 

 through distances of several hundred miles, but it does not 

 seem improbable that the finer particles may remain suspended 

 while the wind makes a complete circuit of the globe. I wit- 

 nessed on March 31st and April 1st, in 1863, a dust-fog at 

 Nagasaki which lasted two days, and left only a just percepti- 

 ble film of dust, observable only on the white, newly painted 

 deck of a yacht. A similar fall occurred simultaneously at 

 Shanghai, and both were contemporaneous with a terrific dust- 

 storm which during two days shrouded the country about 

 Tientsin in deep darkness. 



I am indebted again to Mr. Clarence King for the state- 

 ment that dust-fogs occur on the coast of California with the 

 prevailing west wind ; and this may be, as he suggests, the 

 finest residuum of the loess-dust of an Asiatic dust-storm.* 



Concerning the power of wind to transport dust, many 

 other striking illustrations have been noted. Showers of red- 

 dish dust occasionally fall upon ships far out at sea. Darwin 

 describes one such storm encountered by him near the Cape 



* "American Journal of Science," vol. cxvii, 1879, pp. 133, 134, 139. 



