134 DEPARTMENTAL REPORTS. 



The investigations of the influence of dissolved salts on the capil- 

 lary rise of soil moisture have also been continued. This subject has 

 an important bearing upon the treatment of alkali lands. It was 

 found that dilute solutions of neutral salts have practically no influ- 

 ence upon the capillary action, while concentrated solutions of all 

 salts materially diminish the extent of the capillary movement. In 

 the case of the alkaline salts, however, the capillary rise is consid- 

 erably greater than for neutral salts of the same concentration. A 

 detailed description of these results and their practical bearing is now 

 in course of publication. 



RELATION BETWEEN CARBONATES AND BICARBONATES IN ALKALI SOILS. 



In continuation of the work on carbon dioxide an investigation has 

 been made in connection with the chemical laboratory of this Division 

 of the equilibrium between carbonates and bicarbonates in solutions 

 of various concentrations and temperatures. The economic bearing 

 of this investigation and the results obtained will be further referred to. 



SPECIAL APPARATUS. 



The special electrical apparatus devised in the physical laboratory 

 for the investigation of soluble salt content of soils is now being 

 extensively used by the field parties in the alkali investigations in 

 the West. A filter has recently been devised for the removal of sus- 

 pended clay from soil solutions, and has been found very useful in 

 the field and laboratory. Perfectly clear soil solutions can be quickly 

 obtained by its use, and chemical determinations in the field which 

 were formerly difficult or impossible on account of the suspended clay 

 can now be readily carried on. 



MECHANICAL SOIL ANALYSIS. 



During the past year 640 complete mechanical soil analyses have 

 been made. These analyses have been restricted almost entirely to 

 the examination of the various soil types established by the field par- 

 ties, serving as a check upon the field classification and as a matter 

 of information regarding the mechanical texture of the soils. The 

 method of analysis, which involves the use of a centrifugal apparatus 

 to separate the sand and clay, is much more rapid than the methods 

 formerly employed, and two men can now readily make 50 complete 

 analyses a week. 



USE OF PHOTOGRAPHY. 



Photography has become a valuable adjunct to the work of the 

 Division, both in illustrating the characteristic features of the areas 

 surveyed and in the preparation of the base maps for field use. The 

 topographic sheets of the Geological Survey are used as base maps 

 whenever available, but frequently we are dependent upon county 

 atlases or other maps. These maps naturally vary greatly as to scale, 

 but can be readily and quickly reduced by means of photography to 

 the uniform scale of 1 inch to the mile, used in the work of the Divi- 

 sion. For this purpose a modest photographic equipment for enlarg- 

 ing and reducing has been installed. Photographic paper used is also 

 prepared at small cost in the laboratory, and the preparation of the 

 base maps can now be rapidly and economically carried on. 



