8 



plained by MIDDENDORFF, WALTHER (p. 122) and SOLGER (p. 

 149). In contrast to the dunes of western Europe, the barchans 

 do not owe their occurrence to the sand having at first found 

 shelter behind some obstacle, but they take that form which 

 offers least resistance to the wind, hence they must be regarded 

 as gigantic wave- lines in the sand. Good pictures of barchans 

 may be seen in BESSEY. 



Other forms of sand landscapes are dealt with in the 

 chapter on the formation of the sand desert. 



The Aralocaspian formations which originated in the 

 post-pliocene Aralocaspian Basin consist of sandy clays de- 

 posited on the bottom of the basin. The area of the older 

 sea was considerably larger than that of the present lakes; 

 thus, its eastern part extended down both sides of the isolated 

 mountains Bukan Tau and Sultan Uis Dagh so that these 

 occupied a peninsula in the sea. As the sea dried up, many 

 smaller lakes were left. 



Loess, as is well known, is a calcareous loam inter- 

 sected by innumerable irregular veins which often contain 

 roots of plants. "Ein Leichenfeld von unzahlbaren Genera- 

 tionen von Grasern", as RICHTHOFEN puts it (I, p. 71). Loess 

 is now generally regarded as an eolian deposit derived from 

 dust-drift, since the finest material shifted by the wind if 

 not taken right away must sooner or later come to rest 

 either in water or on a fixed " steppe", because the wind 

 would carry it away again from any other place (RICHTHOFEN 

 I, p. 98). In the first case the material will go to form stra- 

 tified deposits on the sea-bottom, in the latter it will form 

 land-loess which is not stratified. 



In Turkestan Loess may attain a great thickness, accor- 

 ding to ROMANOWSKI up to 1500 feet. It occurs more especi- 

 ally in the south-eastern, southern and eastern parts of the 

 territory, but also occurs in patches in other places (Musn- 

 KETOW). 



Like all areas without drainage to the sea, the Trans- 

 caspian plains are rich in salts, since if the products of 

 disintegration and chemical weathering cannot be taken out 

 of the country, they must remain. Most of the Russian 

 authors known to me are of opinion that the salts origin- 



