Alkali Carbonate Solution, 105 



into the perplexing alternations in the nature of the soluble 

 salts existing in alkali soils, even in closely contiguous spots ; 

 the alkali carbonates predominating in one spot, while in 

 others, not many yards away, sulphates and chlorides are 

 altogether predominant. A detailed discussion shows that 

 the carbonate almost always occurs in the lower, moister and 

 denser soils, while the neutral salts predominate on the higher 

 ground, and in open soils. Moreover, the carbonate always 

 exists in larger relative proportion in the depths of the soil, 

 where at times the, carbonate of soda forms the almost exclusive 

 ingredient f" showing clearly that, wherever in the soil column 

 carbonic acid is continually formed and retained, by fermenta- 

 tive or oxidation processes, the formation of carbonate pre- 

 dominates ; while near the surface, under the influence of aera- 

 tion, the reverse process gains ascendency. 



The Alkali Carbonates as a geological agency, — The pow- 

 erful chemical effects of alkali carbonates upon the rock ingre- 

 dients hardly require discussion. From the radical results 

 obtained in their fusion with silicates in the laboratory, to the 

 more gentle action exerted by alkaline carbonated mineral 

 waters in dissolving and redepositing silica, whether in the 

 form of sinter or of gold-bearing quartz veins, there is a wide 

 range of possible and probable reactions, less incisive than the 

 former, and more so than the latter, that will readily explain a 

 good many recondite as well as common phenomena of meta- 

 morphism as well as of vein formation, without resort to 

 violent hypotheses. Investigation has not yet progressed far 

 enough to teach us what may be the measure and direction of 

 the above reactions under the increase of heat and pressure, 

 which is so common a factor in geological deposits, and which, 

 with one accord, we connect with the phenomena of rock 

 metamorphism. The liquid carbonic dioxide, found inclosed in 

 quartz crystals, suggests forcibly to what extent the intensity 

 of the reactions in which it participates may be carried in the 

 depth of the earth ; and how under heavy pressure its mere 

 preponderance of chemical mass may, in the case before us, 

 intensify and multiply the reactions. 



Free carbonic acid, impregnating, in presence of earth carbon- 

 ates, any solution of alkali salts, will form a solvent of ampho- 

 teric reaction, both alkaline and acid in its solvent effects ; 

 corresponding in the body of the earth to that other ampho- 

 teric solvent, the hydrosodic and hydropotassic phosphates, 

 which play so important a part in vegetable and animal bodies. 

 In regard to the formation of deposits of metallic minerals we 

 need but remember the facility with which alkali sulphids are 



* See Bulletin of the Cal. Exp, Station No. 108, " The distribution of the salts 

 in alkali soils "; also Report of the same for 1894-95. 



