528 THE FRESH-WATER LOCHS OF SCOTLAND 
These plateaus separate the lowlands of Siberia and the Aralo-Caspian 
depression from the lowlands of Mesopotamia, India, and China to 
the south, and together with the Aralo-Caspian depression form most 
of the inland drainage area of the continent. The lower terrace of 
the eastern plateau, which is occupied by Eastern Turkestan in the 
west and by the Desert of Gobi in the east, is known as the Central 
Asian depression ; but as its altitude varies from 3000 to 4000 feet 
in the highest part to 2200 feet in the lowest — the depression of 
Lob Nor — the term must be taken as purely relative to the height 
of the surrounding plateau. 
It has long been surmised by historians that certain parts of Asia 
have been growing more arid, and the phrase, "the desiccation of 
Asia,'' has been much used in this connection. But while some 
employ it to denote the process of change from the coldness or 
moisture of the Glacial period to the comparative aridity of the 
geological epoch of to-day, and maintain that this process is accelerated 
by that gradual elevation of parts of the continent which led to the 
separation of the Tertiary inland seas, and which is still in progress 
at the present time," others take it as meaning a gradual change in 
climate supposed to have taken place during the period covered by 
history. Bruckner,^ from a study of meteorological records and of 
the fluctuations in the level of the Caspian and other isolated lakes, 
comes to the conclusion that the variations of climate form a cycle 
of thirty-five years. WoeikofF,^ basing his reasoning on recent 
Russian investigations on Central Asian lakes, such as those of Berg 
on the Sea of Aral, and on the examination of the meteorological 
records for the town of Barnaul in Western Siberia, for which a 
longer series is available than for any other Asiatic station, adopts 
the theory that if variations are recurrent the period must extend 
over at least sixty years ; but as records of meteorological observations 
date back little more than one hundred years the precise length can- 
not be determined for some considerable time. Central Asia he 
considers to have just passed through a minimum phase. Ellsworth 
Huntington ^ holds that, between the recurrent glacial epochs at one 
end of the scale and the climatic variation at the other there is an 
intermediate pulsation, the beats of which are to be reckoned by 
thousands of years and will be coincident with regular fluctuations of 
rainfall and temperature throughout the world. 
1 Kropotkin, " The Desiccation of Eur-Asia," Geogr. Journ., vol.xxiii.p. 724, 1904, 
2 Kropotkin, "The Orography of Asia," Geogr. Journ., vol. xxiii. p. 346, 1904. 
3 Kiimaschwankungefi seit 1700, Wien, 1890. 
4 " Der Aral See und sein Gebiet nach den neuesten Forschungen," Petermann 
Mitt., Bd. Ixv. p. 82, 1909. 
° The Pulse of Asia, London, 1907. 
