103 



ANNALS NEW YORK ACADEMY OF SCIENCES 



We may say, therefore, that the consecutive curves of temperature for 

 the United States, if compared with the Arequipa curve, may belong to a 

 direct type similar to the Arequipa variation (considered as a standard 

 of the equatorial or direct variation), or to an inverse type.^" Some 

 curves, it may be added, must be called indifferent, since, to a certain 

 extent, they belong to both types of variation at the same time. Finally, 

 there is the independent type. 



Fig. 56. — Comparison of variations in California and Texas icith tlie Arequipa curve 



Most curves may belong, temporarily, to one type or the other, but this 

 is not a complication, because, if the results gained from the comparison 

 of the consecutive maps are kept in mind, it is plain that it could not be 



^ Compare the maps published by Frank H. Bigelow : "Studies on the circulation of 

 the atmospheres. . . ." Monthly Weather Review, Vol. 31, p. 515. Washington, 

 1903. Also : Sir Norman Lockyer and Wm. .T. S. Lockyer : "The behaviour of the 

 short-period atmospheric pressure variation over the earth's surface." (Proc. Roy. Sec. 

 London, Vol. 73, p. 457. London, 1904.) 



