CHANGES OF CLIMATE 463 



earlier than during the preceding century, but three days later than 

 during the second century preceding. At the present time, the average 

 date of the grape harvest in Aubonne is exactly the same as at the close 

 of the sixteenth century. After a careful study of the conditions of the 

 date tree, from the fourth century, B. C, Eginitis concludes that the 

 climate of the eastern portion of the Mediterranean basin has not 

 changed appreciably during twenty-three centuries. In China, a com- 

 parison of the ancient and present-day conditions of cultivation, of silk 

 production, and of bird migrations, has led Biot to a similar conclusion. 

 In some cases, the reported cultivation of cereals, or other soil products, 

 in certain at present unfavorable climates has been shown to be purely 

 a myth; as in the case of a supposed extended cereal cultivation in 

 Iceland in former times. 



Secondly, a good many of the reports by explorers from little-known 

 regions are contradictory. Thus Lake Aral, which was diminishing in 

 area for many years, is recently reported by Berg as increasing. Lake 

 Balkash, which was rapidly drying up, has also begun to fill again. 

 Partly submerged trees are noted as having been seen by Berg, who in 

 June, 1902, found the lake waters quite fresh. As the lake has no 

 outlet, this is an interesting fact. In Africa, Lake Victoria which, it 

 was generally agreed, was sinking in the period 1878-1892, has since 

 shown a tendency to rise. Lake Bukwa, east of Tanganyika, has risen 

 within the last few years. Beports that the Sea of Azov is drying up 

 have been explained as due to a silting up of a lake. Lake Chad is 

 very probably subject to oscillations, sometimes spreading beyond its 

 usual limits as the result of several years of heavy rainfall. Such 

 diverse reports show the need of caution in jumping at conclusions of 

 climatic change. An increased use of water for irrigation may cause 

 the level of water in a lake to fall, as has been the case to some extent 

 in Great Salt Lake. Periodic oscillations, giving higher and then 

 lower water, do not indicate progressive change in one direction. Many 

 writers have thus seen a law in what was really a chance coincidence. 

 Partsch believes that the ancient settlements on the interior lakes of 

 northern Africa show that these lakes contained no more water formerly 

 than they do now. Some have claimed that the supposed desiccation of 

 the climate of northern Africa resulted from deforestation, but no cer- 

 tain evidence exists of the presence or destruction of such forests, and 

 if deforestation did take place, no considerable change of climate could 

 have resulted. 



Thirdly, where a progressive desiccation seems to have taken place, 

 the question should be asked, is less rain actually falling, or have the 

 inhabitants less capacity, less energy, less ability than formerly? Is 

 the change from a once cultivated area to a barren expanse the result 

 of decreasing rainfall, or of the emigration of the former inhabitants 



