must on no account be raised to levels which would effect crops by seepage of water 

 from new canals. Seismological parties are studying the structure of geological strata 

 by measuring tremors caused by explosions. 



Meteorological stations have been set up in many places in the Caspian lowlands 

 and Asian deserts to collect data which, among other things, may give information 

 concerning the origin of the dry desert winds referred to above, and assist in com- 

 bating sandstorms. A special laboratory for the study of sandstorms has been set up 

 in the Ashkhabad by the Turkmenian branch of the Academy of Sciences of the U.S.S.R. 



Protection of both canals and of irrigated land in the desert against shifting sand 

 and wind are essential. Shelter belts of poplar trees can be quickly grown when 

 watered; they now form wind breaks round the fields of Tashkent and other oases, but 

 unlike the steppe forests, these poplar windbreaks depend on irrigation. Altogether one 

 and a quarter million acres of desert forest will be grown to shelter the canal and the 

 watered land; this work is co-ordinated by a special Ministry of Forestry for the con- 

 struction schemes. The Black Saxaul tree grows without irrigation in the desert, and ' 

 was once more widespread in occurrence than at present, having been cut down for fire 

 wood. In the summer of 1951 seeds of this tree were collected, and in the spring of 

 1952 were sown over large areas by parties operating from camels (this traditional ship 

 of the desert is now very little used). The black saxaul sends its roots down to a 

 depth of 30 feet, thus fixing the soil as well as gaining moisture, and in 10 years it 

 can reach a height of 20 feet and a trunk girth of 1 foot. The controlled use of this 

 tree should provide substantial yields of timber within 25 to 30 years. Ash, white 

 acacia, apricot and mulberry will also contribute to the shelter belts when the water 

 comes, and smaller species of sand fixing vegetation and saplings are now being 

 planted on a large scale. For the protection of young trees wind screens made of reeds 

 have proved to be more satisfactory than solid ones. Impervious sheets hold back all 

 the sand, and produce dunes before becoming buried. The setting up of the screens 

 in sand is mechanised. Experiments are also in progress on the utilisation of a waste 

 product from industry which, when sprayed on to sandy soil, will immobilise the sur- 

 face, yet leave it permeable to rain and to vegetation. 



There is much work connected with the irrigation of the desert which is of indirect 

 biological importance. Seepage outward from canals is being checked by packing with 

 clay, concrete or asphalt being prohibitively expensive. Intense rates of evaporation 

 will lead not only to the loss of high percentages of the water entering the Turkmenian 

 canal, but also to silt deposition and a tendency for the water to become saline. The 

 silt content of the canal water is estimated to reach 20- 25 million tons, and when de- 

 posited will be removed by electric excavators and suction dredgers, besides by silt 

 eliminators such as those already in use in Uzbekistan. These are floating instal- 

 lations which, by stream directing shields, allow only pure water to enter a canal, 

 thereby reducing the cost of cleaning out the canal to one tenth of its previous figure. 

 Again a special centre, the All -Union Scientific Research Institute for Hydro -tech- 

 nique and Amelioration, is dealing with this work. 



The other side of the scientific work concerns the productivity of the watered 

 desert, and this is being prosecuted in laboratories as far apart as Moscow and Tash- 



151 



