332 Journal, of Agricultural Research voi. x, no. ? 



of lime, ■which is largely present in the soils at the foot of the Rocky Mountains and 

 Sierra Nevada series, by means of carbonate of soda occurring as efflorescences on soil. 

 The usual origin of sulphate of soda is either directly from volcanic sources, or by the 

 delivery of springs containing salt derived from preexisting sedimentary beds. In 

 a few cases it is derived from the oxidation of sulphur in bituminous strata, or in 

 pyritiferous beds which, reacting on common salt, produce thenardite or other forms 

 of sodic sulphate. 



In 1 876 the East India Government on petition appointed a coinmittee 

 to investigate and report on the increasing encroachments of "reh," a 

 saline efflorescence on soil irrigated by canals. One member of this com- 

 mittee, Mr. Medlicott, Superintendent of the Geological Survey of India, 

 says (6), regarding the origin of "reh": 



Every one seems content to accept the reh as an ultimate fact — ^that there it is — as 

 much an original ingredient of the ground as the clay and sand. Now, I consider it 

 demonstrated that this view is false, and that an origin is assignable for reh which 

 introduces the gravest apprehensions as to the possible results of canal irrigation, 

 The present chief store of reh is in the saline subsoil-water — ^the upper water-bed 

 found more or less all over Upper India. Beneath this, at depths of from sixty to 

 one hundred feet, sweet water is found, containing no more salt than the canal water, 

 which is very pure. Now, I consider it certain that these upper deposits were origi- 

 nally as free from those salts as is now the alluvium of the delta; and that the present 

 state has been brought about in the course of generations, slowly but with increasing 

 rapidity, owing to the total subversion of the natural climatal conditions, chiefly 

 by the total destruction of forest vegetation. The explanation is simple: every soil 

 contains some reh, and all percolation water from soils is also contaminated by those 

 salts, which are the refuse products (the parts unassimilated by vegetation) in the 

 very slow process of formation and consumption of soil. Unless removed it must 

 accumulate ; and the natural process of purification is a certain necessary amount of 

 percolation and ground drainage, the pure rain-water passing through the soil carrying 

 off any iijjurious excess of these rejected salts. If the washing process is sufficiently 

 free to insure a certain discharge of this percolation water by natural subsoil drainage, 

 there will be a constant dilution and removal of the subsoil-water; but if the percolation 

 through the soil is no more than to restore what has been dissipated by capillary action 

 and evaporation during the dry season, the reh will go on accumulating in the upper 

 water-table; and such has been the condition of Upper India for many a day. 



Hilgard, soon after the beginning of his association with the University 

 of California in 1874, began his classical work upon the various phases 

 of the alkali problem. In his report to the president of the university 

 in 1877, he says (5, p. 43), in a discussion of the origin of alkali: . 



The immediate source of the alkali is usually to be found in the soil water, which, 

 rising from below and evaporating at the surface, deposits there whatever of dissolved 

 matters it may contain. 



And the manner in which it gets its way into the soil water is fully 

 discussed in the numerous subsequent publications on the subject by him 

 and possibly is fully represented by the following direct quotation (6, 



P- 9): 



The same alkali salts are formed everywhere in the world ; but in countries having 

 abundant rainfall they are currently washed, as formed, into the country drainage, 

 while in regions where rainfall is deficient, the scanty moisture only carries them a 



