830 EXPERIMENT STATION RECORD. 



Massachusetts. The purity of natural ice in relation to its source, and of artificial 

 ice in relation to the process of manufacture followed, is discussed. 



A soil study. Ill, The soil, W. P. Headden {Colorado Sta. Bui. 6.5, 2JP- 56). — 

 Previous bulletins (parts I and II) contain the results of observations on the effects 

 of the mechanical condition, the alkalis contained in, and the general properties of 

 the soil of a plat on the college farm, upon the crops grown on it. This bulletin 

 reports a continuation of this investigation, but deals exclusively with the chemical 

 and physical study of the soil used in the i)revious experiments. The soil, which 

 "varies in its character from a loamy soil with a calcareous, clayey sub.soil, to a fine 

 alluvium resting upon a stratum of gravel, separated from it by a rather compact 

 clay, but with no proper hard pan," was chosen because "it was considered to be the 

 most strongly alkalized plat to be found on the college farm." Examinations of this 

 and other soils of the eastern slope of the Rocky Mountains and of the plains lying 

 to the east in Colorado are reported, which show that these soils are in general very 

 similar in chemical (mass analysis) and mineralogical composition, the principal 

 variations in the latter respect being in the ratio of the quantities uf the minerals 

 present. "The surface soils of this section of Colorado prol)al)ly owe their mineral 

 constituents to a common source, the schists and granites of the Colorado range." 

 Feldsi)ar (orthoclase) is an almost universal constituent, and according to the sand 

 cultures with oats reported "serves as a source of potash and also of hydrous silicates 

 under ordinary cultural conditions. . . . This fact is of great importance to our 

 western agriculture, especially to the agriculture of the eastern slope of the Rocky 

 Mountains and eastward to the State line, as the irrigable lands are composed largely 

 of granitic materials and consecjuently contain a more or less considerable quantity 

 of feldspar, whose decomposition yields, slowly it may be, but a continuous sujjply 

 of this very important compound. . . . The theory of the formation of zeolitic 

 minerals, to serve as conveyors of tiie potash, etc., from the more stable minerals to 

 the plant, can not very well be ai)pealed to, at least as necessary. My experiments 

 do not show that zeolitic compounds are not formed, but they do show that if they 

 are formed their formation takes place so rapidly that perfectly fresh, but finely 

 pulverized, feldspar becomes an available source of potash in the short period 

 required for the growth of the oat plant. . . . 



"The alkali salts in the soils and waters of Colorado are essentially mixtures of 

 the sulphates of lime, magnesia, and soda. . . . Relative to the origin of such quan- 

 tities of sulphates ii these rocks and soils, the possible supply is abundant, for 

 throughout the moun ain masses we find sulphids disseminated everywhere, and we 

 have an almost inexhaustit)le source of sul{)huric acid for the formation of alkali in 

 the gypsum which is so abundant in our Jurassic and other formations." 



It is shown that by the analyses reported that the composition of the water-soluble 

 portion of the soil studied differs both from that of the incrustations of alkali formed 

 on the surface and from that of the portion in solution in the ground water. "The 

 incrustations are formed by the evaporation of water from the surface of the soil, 

 which, owing to the deportment of the solutions of these salts toward capillary 

 action, and the chenucal instability of the hydrated salts themselves, effects their 

 separation from the soil solutions. . . . The i)redominant s<jluble salt in the soil is 

 calcium sulphate, that in the alkali which effloresces from this ground is sodium sul- 

 phate, with magnesium sulphate second in quantity, while the calcium suljjhate is 

 but little greater than the sodium chlorid. . . . 



"The formation of these incrustations effects a rough sejjaration of the markedly 

 efflorescent salts, sodium and magnesium sulphates, from the permanent calcium 

 sulphate. Ordinary salt, sodium chlorid, which is present, is also concentrated in 

 the alkali, but not nearly to a like extent, as those already named. The highest fig- 

 ure obtained for the sodium sulphate in any sample of the water-soluble is in the 

 first 2 in. of a soil in which it amounts to 27 per cent. In the alkalis it is practically 



