FERTILITY OF DIFFERENT SOILS. HI 



often present, having in most cases entered the plants by means 

 of alkalies. In order to form a distinct conception of the quan- 

 tities of alkalies in aluminous minerals, it must be remembered 

 that felspar contains 17 J per cent, of potash, albite 11*43 per 

 cent, of soda, and mica 3 — 5 per cent. : — and that zeolites con- 

 tain, on an average, 13 — 16 per cent, of alkalies.* The late 

 analyses of Ch. Gmelin, Lowe, Fricke, Meyer, and Redten- 

 bacher, have also shown, that basalt and clinkstone contain from 

 J to 3 per cent, of potash, and from 5 — 7 per cent, of soda ; that 

 clay-slate contains from 2-75 — 3-31 per cent, of potash, and 

 loam from l£ — 4 per cent, of potash. 



If, now, we calculate from these data, and from the specific 

 weights of the different substances, how much potash must be 

 contained in a layer of soil, formed by the disintegration of 26,- 

 910 square feet (1 Hessian acre) of one of these rocks to the 

 depth of 20 inches, we find that a soil derived from 



Felspar contains - - 1,152,000 lbs. 



Clinkstone " from 200,000 to 400,000 " 



Basalt " " 47,500 " 75,000 " 



Clay-slate " " 100,000 " 200,000 " 



Loam " " 87,000 " 300,000 " 



The alkalies, potash, and soda, are present in all clays ; at 

 least, they have been found in all the argillaceous earths in 

 which they have been sought. The fact that they contain potash 

 may be proved in the clays of the transition and stratified moun- 

 tains, as well as in the recent formations surrounding Berlin, by 

 simply digesting them with sulphuric acid, by which process 

 alum is formed. (Mitscherlich.) It is well known also to all 

 manufacturers of alum, that the leys contain a certain quantity 

 of this salt ready formed, the potash of which has its origin from 

 the ashes of the stone and brown coal, which contains much 

 argillaceous earth. 



A thousandth part of loam mixed with the quartz in new red 

 sandstone, or with the lime in the different limestone formations, 

 uffbrds as much potash to a soil only twenty inches in depth as 

 is sufficient to supply a forest of pines growing upon it for a 



* Recent investigations have shown that potash felspars always contain 

 a certain quantity of soda, and that sdda felspars always contain potash. 



