CORRELATION OF DISTRIBUTIONAL FEATURES. 523 



maximum length is very similar in the two, being 237 days for the 

 Upper Sonoran and 241 days for the Carolinian, but the minimum 

 value for the former is 25 days and for the latter 127 days. Whereas 

 the moisture conditions of the Alleghanian Zone were found to lie well 

 within the extremes for the Transition Zone we ha,ve in the case of the 

 Upper Sonoran and Carolinian Zones a more sharp separation of the 

 ranges of these conditions. In every case there is an overlapping of 

 moisture conditions, by which the minimum values of the Carolinian 

 are seen to be lower than the maximum values for the Upper Sonoran. 

 This circumstance is duer to the fact that the highest moisture values 

 of the Upper Sonoran are registered on the Pacific coast, while the 

 lowest values of the Carolinian are experienced along the one-hundredth 

 meridian. 



The minimum sunshine values for the Carolinian and Upper Sonoran 

 Zones are very similar, but the amplitude of the former is only half 

 that of the latter. The moisture-temperature index is higher in its 

 extreme values and wider in its amplitude in the Carolinian Zone, 

 • reaching a maximum which is about midway of the amplitude for the 

 United States. 



Among the relatively narrow amplitudes for this zone should be 

 noted the normal daily mean precipitation for the average frostless 

 season and the number of days in the longest normal dry period 

 within that season. It is of interest to no^e that the length of the dry 

 period shows a narrow amplitude in the Carolinian Zone, indicating 

 its critical limiting importance, whereas the longest rainy periods are 

 demonstrated to have a critical value for the Upper Sonoran. Con- 

 versely, the length of the rainy period shows a wide, but imperfectly 



TCMPeKATUMC 



Oats in Normal Frostlch Scaion (F. S.) 

 Hot Davs. F. S. ' 

 Colo Oats, F. S. . 



Phtsiolocical Summation, F, S, C 



Normal Dailt Mcan. coldest 14 oats of Ycar C 



Normal Dailt Mean, Ycar C 



PfltCIRITATIOH 



Normal Oailv Mean. F. S. 



DATS IN LONGEST NORMAL RaiNT PERIOD, F. S, 



DATS IN LONStST Normal Drt Period, F. S. 

 Mean Total. Year 



Cvaroration 

 Daily Mean, 1867-6, F. S. Q 



Moisture Ratios 

 Normal P/e. F. S. C 



Normal rr/E. F. S. C 



Normal P/E, Year C 



humioitt 

 Normal Mean, F. S d 



Sunshine 

 Normal Dailt Duration. F. S. IZ 



MOISTURC-TCMRERATURE INDICES 



Normal P/E x T, F. S., Pmtscolocicai Method C 



Fig. 40. Climatic extremes for the Carolinian Zone. 



