656 



POPULAR SCIENCE MONTHLY. 



California 9 



Arizona 7 



Washington 5 



Oregon 3 



Colorado 2 



Kansas 2 



North Dakota 2 



Oklahoma 2 



South Dakota 2 



Nevada 



Montana 



Nebraska 



Iowa 



Illinois 



While the number of reported storms is too small to warrant a 

 discussion of their geographical distribution in the United States, 

 the above table so far, no doubt, correctly represents the facts 

 that it shows an increase from the Western plains to the Pacific 

 coast, and comes to a maximum in the Southwest. On the plains 

 most places are reported to experience dust storms two or three 

 times in a year, while on the Pacific coast estimates and records 

 for different places range considerably above this number. At 

 Los Angeles, Cal., one observer says that there are " two or three 

 in the course of a year, possibly a few more." From Yuma, 

 Ariz., the statement comes that " any high wind, without rain, 

 generally blows clouds of dust," and six sand storms were recorded 

 by observer A. Ashenberger in the Weather Bureau station at that 

 place during 1893. At Ontario, Cal., it is estimated that there are 

 from twelve to forty dust storms in a year. It is said that these 

 storms are " most common and strongest in passes in the mountain 

 ranges in California," that they are " very severe on the east side 

 of the Coast Range," and that " nearly every part of California is 

 afflicted [by them] at times." From the reports which are at 

 hand an estimate of the minimum frequency of these disturbances 

 in places in the West, where topographical and climatal condi- 

 tions do not forbid them, is two in a year for the territory east of 

 the Rocky Mountains and five in a year for the Great Basin and 

 the western slope. A maximum estimate would be four annually 

 for the former region and twenty for the latter. 



Data on the areal extent of each separate storm are meager, as 

 reports of simultaneous observations have been secured in but 

 few instances. Where such observations have been reported they 

 represent, as is evident, the minimum extent of the storm in one 

 direction, since it may have extended beyond the points from 

 which the reports have come. The few instances of reported 

 areal extent of dust storms may be tabulated as follows : 



Artfcd Extent of Single Storms. 



From Milton, Ore., to Colfax, Wash 80 miles. 



" Fresno, Cal., to Santa Maria, Cal 120 " 



" Mojave, Cal., to Oceanside, Cal 140 " 



" Salem, S. Dak., to Sanborn, N. Dak 216 " 



" Santa Anna, Cal., to San Diego, Cal 270 " 



" Over the greater part of Nevada " 300 " 



Over most of northern Iowa and Illinois 400 " 



