Mat 11, 1906.] 



SCIENCE. 



727 



division, giving higher extremes, ranges and 

 means. The temperature records of south- 

 western Arizona (including Tinajas Altas) 

 during the summer of 1905, in fact, fall 

 into three groups or classes, viz: (1) the 

 mountain class, represented by Kingman; 

 (2) the interior plains class, comprising 

 Aztec, Mohave, Mohawk, Parker and Sen- 

 tinel; and (3) what may be called the Gulf 

 class, represented by Yuma and Tinajas 

 Altas. Denoted by their more striking fea- 

 tures, these may be considered, respectively, 

 the cool, the hot and the equable varieties or 

 phases of southwestern Arizona's summer 

 climate. These are illustrated in the ac- 

 companying Table IV., compiled chiefly 

 from Jesunofsky's report for July;^^ two 



classes. The classes of climate or their 

 districts might be defined also by moisture 

 (vapor, precipitation, or both) though they 

 intergrade; in general it may be said — 

 though the qualifying factors are many — 

 that the vapor-content decreases and the 

 precipitation increases east and northeast 

 of the gulfward zone represented by Yuma 

 and Tinajas Altas. 



GENERAL INTEEENCES. 



Through earlier observations in Arizona, 

 Sonora and California the coastwise zone 

 commonly called the fog-belt — an irregular 

 zone extending inland from three to 

 twenty-five miles (according to local con- 

 figuration) from the Pacific and Gulf 



TABLE IV. — CLiMATAii TYPES OF WESTERN ARIZONA. (Defined by Temperature Records for July, 1905.) 



typical stations of the southern division 

 being introduced partly to illustrate the 

 extension eastward of the two interior 



' Not given in Jesunofsky's tables. 



' Introduced from adjacent ' division ' for com- 

 parison. 



"Computed from Jesunofsky's figures (excepting 

 Tinajas Altas) . 



^° Excluding Mohawk and Sentinel records, 

 in which actual minima do not appear. 



" Published at Phtpnix, August 22, 1905. Other 

 monthly reports are entirely consistent, though 

 not accessible at this writing. 



coasts— was well known, and its dominant 

 influence on flora and fauna was under- 

 stood; and the recognition of this zone led 

 naturally to inferences concerning the more 

 striking climatic features of Tinajas Altas 

 and Yuma. So the records were soon seen 

 to indicate the existence of a zone parallel 

 with and inland from the fog belt which 

 may be both denoted and described as a 

 vapor belt, i. e., a zone in which the ag- 

 gregate volume of aqueous vapor is con- 



