248 PROF. G. F. WRIGHT ON RECENT GEOLOGICAL [May I9OI, 



through the Ceutral plateau eroded valleys several miles wide and 

 of great depth, having evidently, in the period of their history, 

 brought down sediment enough to have filled the depression many 

 times over. It is significant also that the lake is now inhabited 

 by a species of seal closely allied to those found in the Caspian Sea. 



Passing over the low-lying region west of the Yenisei River, we 

 ascended the Irtish lliver from Omsk to Somipalatinsk, and travelled 

 by tarantass to Tashkend, 1200 miles along the base of the high 

 mountains which form the border of the Central Asiatic Plateau on 

 the north-west. Our route took us through Sergiopol and south of 

 Lake Balkash, through Kopal, Yeruoe, Tokmak, Auleata, Chimkent, 

 Tashkend, Samarkand, and Merv to the Caspian Sea. As far as 

 Tashkend the Ala Tau and Alexandrovsky Mountains rose imme- 

 diately to the south of our route, to heights frequently reaching 

 1 5,000 feet. The general elevation of the road was between 2000 and 

 3000 feet, while the latitude is about that of Switzerland. Eut while 

 Ijcal glaciers can be frequently seen in the higher portions of the 

 chain, and the water of nearly all the larger mountain-streams is to 

 some extent turbid with glacier-detritus, there are no signs that 

 glaciers ever deployed out upon the plains as they did from the Alps 

 during the Glacial Period. 



Por 600 miles, however, between Vernoe and Samarkand, our route 

 lay over a broad terrace of loess, in many pPices certainly 100 feet 

 thick. This constitutes the fertile irrigated belt of territory which 

 gives importance to Turkestan, and furnishes valuable data for the 

 interpretation of the problems of post-Pliocene geological movements. 

 The belt of loess is of varying width, and; merges gradually into the 

 drifting sands of the deserts to the north. It is present in special 

 abundance in the valleys of the Hi, the Chu, the Sur Daria, and the 

 Amu Daria Rivers. It is on diametrically the opposite side of the 

 Central Asiatic Plateau from the similar deposits in China, while 

 they are so persistent, so continuous, and so extensive, that nothing 

 but a wide-spread submergence of the region to the extent of 

 about 3000 feet would seem to explain the phenomena. 



]*^or is contributory evidence of such a submergence wanting. 

 Lake Balkash, about 1000 feet above the sea,, has no outlet ; yet I 

 was told by the geologists in St. Petersburg that its water is nearly 

 fresh. This indicates that a comparatively short time has elapsed 

 since it discharged its waters into some lower basin. The Aral 

 Sea, also, has no outlet, and its waters are only brackish. 'No 

 long time can have elapsed since it discharged into the Caspian Sea 

 through the well-marked dry channel that can be easily traced 

 between the two basins. The saltness of the Caspian Sea is also 

 only about one third; that of the ocean. The innumerable dried-up 

 lakes which had no extensive tributaries are now salt-beds. 



All this indicates very recent physical changes in tlie region, of a 

 nature to have great influence upon the climate. Enclosed basins 

 such as these would naturally contain water much Salter than that 

 of the ocean. It is evident, therefore, that upon the emergence of 



