CLIMATE OF HISTORIC TIMES 



535 



from lack of water and provisions. Various other authors, among whom 

 I have been one, have taken the opposite view, and have maintained that 

 the large size of Alexander's army, and especially the presence of ele- 

 phants, prove that the march would have been impossible under present 

 climatic conditions. As a matter of fact, it is extremely doubtful whether 

 any reliable conclusion can be drawn from this one incident when taken 

 by itself. We do not know whether Alexander's march took place during 

 an especially dry or an especially wet year. In a desert region like Ma- 

 kran, in southern Persia and Beluchistan, where the greatest difficulties 

 occurred, the rainfall varies greatly from year to year. We have no rec- 

 ords from Makran, but the conditions there are closely similar to those 

 of southern Arizona and New Mexico. In 1885 and 1905 the rainfall for 

 five stations in that region was as follows : 



1905. 



Mean rainfall dur- 

 ing pel iod since 

 observations 

 began. 



Yuma, Arizona 



Phoenix, Arizona 



Tucson, Arizona 



Lordsburg, New Mexico 



El Paso, Texas (on New Mexico border) 



Average 



2.72 

 3.77 



5.26 

 3.99 

 7.31 



11.41 

 19.73 

 24.17 

 19.50 



17.80 



4.61 



18.52 



3.13 



7.27 



11.66 



8.62 

 9.06 



7.95 



These stations are distributed over an area nearly 500 miles east and 

 west. Manifestly a traveler who spent the year 1885 in that region would 

 liave had much more difficulty in finding water and forage than one who 

 traveled in the same places in 1905. During 1885 the rainfall was 42 per 

 cent less than the average, and during 1905 it was 134 per cent more than 

 the average. Let us suppose, for the sake of argument, that the average 

 rainfall of southeastern Persia is 6 inches today and was 10 inches in the 

 days of Alexander. If the rainfall from year to year varied as much in 

 the past in Persia as it does now in N'ew Mexico and Arizona, the rain- 

 fall during an ancient dry year, corresponding in character to 1885, 

 would have been about 5.75 inches. On the other hand, if we suppose 

 that the rainfall then averaged less than at present^ — let us say 4 inches — 

 a wet year corresponding to 1905 in the American deserts might have 

 had a rainfall of about 10 inches. This being the case, it is clear 

 that our estimate of the importance of Alexander's march must depend 

 largely on whether 325 B. C. was a wet year or a dry year. Inasmuch 

 as we know nothing about this, we' must fall back on the fact that a 



