CHANGES OF CLIMATE 459 



indicates a gradual desiccation from early historical times down to the 

 present day. His study of climatic changes in that region is one of 

 the most thorough ever made, for the evidence of archeology, of tradi-, 

 tion, of history and of physiography has been carefully matched and 

 found to accord in a very striking manner. Huntington has found 

 evidence of the abandonment of successive village sites as the inhabit- 

 ants moved further upstream in search of more water. Patches of 

 dead jungle show that vegetation once flourished where aridity now 

 renders plant growth impossible. 



In northern Africa certain ancient historical records have been 

 taken by different writers to indicate a general decrease of rainfall 

 during the last 3,000 or more years, the remains of cities and the ruins 

 of irrigating works pointing to a larger population and a greater water 

 supply formerly than at present. The presence of certain animals, 

 now no longer found there, is implied by ancient records, and from 

 this fact also a change of climate is inferred. In his crossing of the 

 Sahara between Algeria and the Niger, Gautier found evidence of a 

 former large population. A gradual desiccation of the region is, there- 

 fore, believed to have taken place, but to-day the equatorial rain belt 

 seems to be again advancing farther north, giving an increased rain- 

 fall. Gautier divides the history here into three periods, (1) dense 

 population, (2) aridity, and (3) the present change to a steppe 

 character. 



Farther south, several lakes have been reported as decreasing in 

 size, e. g., Chad, Ngami and Victoria; and wells and springs as run- 

 ning dry. In the Lake Chad district, Chevalier reports the discovery 

 of vegetable and animal remains which indicate an invasion of the 

 Sudan by a Saharan climate. Neolithic relics indicate the former 

 presence there of prosperous communities. Again, to note another 

 instance, it is often held that a steady decrease in rainfall has taken 

 place over Greece, Syria and other eastern Mediterranean lands, result- 

 ing in a gradual and inevitable deterioration and decay of their people. 

 These examples might be multiplied, for reports of climatic changes of 

 one kind or another are numerous from many parts of the globe. 



What Meteorological Records show. — As concerns the popular im- 

 pression regarding change of climate, it is clear at the start that no 

 definite answer can be given on the basis of tradition, or of general 

 impression, or even of the memory of the ' oldest inhabitant.' Human 

 memories are very unreliable things, and there are many reasons for 

 their being particularly untrustworthy in matters of this kind. The 

 only answer of real value must be based on what the instrumental 

 records of temperature, and of rain and snowfall show. Accurate 

 instruments, properly exposed, and carefully read, do not lie; do not 



