SOLUBLE CONSTITUENTS OF SOILS 865 



sary for zeolitic formation. It is, moreover, in a condition of 

 continual moisture, shut off from the oxidizing influence of at- 

 mospheric air, and under the weight of the thousands of fathoms 

 of overlying water which is here in a state of extreme quiescence, 

 being beyond the influence of superficial movements, as waves, 

 tides and currents. These conditions are so widely different from 

 those which exist in the superficial parts of land areas, that 

 they can be regarded as merely suggestive. The same may be 

 said relative to the zeolite (phillipsite and apophyllite) for- 

 mations at Plombieres as described by Daubree.^ Another fact 

 which militates against the theory of zeolitic formation in soils, 

 is the almost universal absence of these minerals in such secon- 

 dary, unmetamorphosed rocks as are the product of the recon- 

 solidation of the same class of materials as in their unconsolidated 

 condition form soils. If they once existed, it would seem strange 

 they have not in some cases at least survived. If formed in 

 soils, why should they not be formed in secondary rocks where 

 the conditions are apparently so much more favorable? 



It would, to the writer at least, seem more probable that the 

 soluble potash of soils exists, not in zeolitic combination, but 

 in some of the numerous decomposition products of feldspar, 

 nepheline, scapolite, etc., to which the name pinite is commonly 

 applied. Such at least is the case in the potash-rich soils of 

 Maryland, examined by R. L. Packard.^ It is possible also that 

 it may exist in compounds allied to glauconite. More probable 

 yet is the supposition that their absorption and retention is due 

 to the colloidal condition into which the silicate minerals have 

 been shown^ to pass under the influence of water and other agents 

 of decomposition. 



The writer has elsewhere* pointed out that, particularly 

 among basic rocks, there may be actually a larger percentage 

 of matter soluble in hydrochloric acid and sodium carbonate 

 solution in rocks ordinarily designated as fresh, than in the 

 debris resulting from their decomposition. This fact he has 

 since emphasized in a paper read at the December (1896) meet- 

 ing of the Geological Society of America, and from which the 

 following statements are drawn. Rock-weathering, it must be 



^Geologie Experimental, pp. 180 et seq. 

 ='Bti11. 21, Maryland Agricultural Experiment Station, 1893. 

 * See Bull. 92, Bureau of Chemistry, and 30, Bureau of Soils. U. S. Dept. 

 of Agriculture. 



*Bull. Geol. Soe. of America, Vol. VII, 1895, p. 355. 



