CLIMATE OF HISTORIC TIMES 527 



time. Moreover, each year, almost, brings new evidence of the great com- 

 plexity of Glacial periods, epochs, and stages. Thus, for many decades, 

 geologists have more and more been led to believe that the climate of the 

 past has been highly unstable, and that its changes have been of all de- 

 grees of intensity. 



PROGRESSIVE DESICCATION DURING HISTORIC TIMES 



Geographers are now debating the problem of the reality of historic 

 changes of climate in the same way in which geologists debated as to the 

 reality of Glacial epochs and stages. Several hypotheses present them- 

 selves. In the first place, the hypothesis of progressive desiccation has 

 been widely advocated. In many of the drier portions of the world, espe- 

 cially between 30° and 40° from the equator, and preeminently in west- 

 ern and central Asia and in the southwestern United States, almost in- 

 numerable facts seem to indicate that two or three thousand years ago 

 the climate was distinctly moister than at present. The evidence in- 

 cludes old lake strands, the traces of desiccated springs, roads in places 

 now too dry for caravans, other roads which make detours around 

 dry lake beds where no lakes now exist, and fragments of dead forests 

 extending over hundreds of square miles where trees can not now grow 

 for lack of water. Still stronger evidence is furnished by ancient ruins, 

 hundreds of which are located in places which are now so dry that only 

 Hie merest fraction of the former inhabitants could find water. The ruins 

 of Palmyra, in the Syrian Desert, show that it must once have been a city 

 like modern Damascus, with one or two hundred thousand inhabitants, but 

 its water supply now suffices for only one or two thousand. All attempts 

 to increase the water supply have had only a slight effect and the water is 

 notoriously sulphurous, whereas in the former days, when it was abun- 

 dant, it was renowned for its excellence. Hundreds of pages might be 

 devoted to describing similar ruins. Some of them are even more remark- 

 able for their dryness than is Niya, a site in the Tarim Desert of Chinese. 

 Turkestan. Yet there the evidence of desiccation within 2,000 years is 

 so strong that even so careful and conservative a man as Hann,^^ pro- 

 nounces it '^^liberzeugend," although in other regions he does not feel that 

 the matter has yet been settled. In all the discussions of the matter, so 

 far as I am aware, no opponent of the hypothesis of climatic changes has 

 ever even attempted to show by careful statistical analysis that the ancient 

 water supply of these ruins was no greater than that of the present. The 

 most that has been done is to suggest that there rnay have been sources 

 of water which are now unknown. Of course, this might be true in a 



^.T. Hann : Klimatoloprie. vol. 1, 1008. p. P.S: 



