THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE III. VOL. II. 



No. v.— MAY, 1885. 



L — The Inland Seas and Salt-Lakes of the Glacial Period. 

 By T. F. Jamieson, F.G.S. 



IN certain parts of the world, wLere the climate is very dry, we 

 find examples of large salt lakes out of which no water ever 

 flows towards the ocean. These lakes are fed by the rains and 

 streams of the surrounding regions, but the evaporation from the 

 surface is so great that it dries up the water as fast as it comes in, 

 so that the lake remains stationary — the influx of water and the 

 amount evaporated just balancing one another. 



The Caspian Sea is the largest example of this nature ; there are 

 also the Sea of Aral, the Balkash, the Dead Sea, and many others of 

 lesser note. 



It is evident, however, that, should any change take place in the 

 climatic condition of the surrounding regions, these lakes would be 

 influenced thereby. 



If it got drier, the water would evaporate faster than it came in, 

 and the lake would diminish in size until an equilibrium was again 

 established, or it might even be dried up altogether and converted 

 into a plain of salt, as has been the case with many small lakes. 

 On the other hand, if the climate grew wetter, the lake would rise 

 in level and, were the humidity to increase enough, would go on 

 enlarging until the water filled the basin ; it would then send out 

 a river over the lowest part of the border, and be converted into an 

 ordinary fresh- water lake. 



In these salt lakes, therefore. Nature has furnished us with a 

 delicate means of detecting the secular changes that take place in 

 the atmospheric moisture of the surrounding regions, and if properly 

 studied, they ought to afford us considerable help in dealing with the 

 history of later geological times. 



A good many years ago I ventured to speculate upon the influence 

 which the Glacial period would have upon these lakes, and in 

 a paper upon a kindred topic published in the Quarterly Journal of 

 the Geological Society (1863, vol. xix. p. 258), I expressed myself 

 as follows : 



" More important effects, however, than these must have followed 

 from the refrigeration of the climate of Central Asia during the 

 Glacial period, and which I have not seen noticed. The great basin 

 of the continental streams, larger than the area of Europe, is re- 

 markable for its inland lakes from whence no streams ever reach 



DECADE III. TOL. II. NO. V. 13 



