No. 129.] 211 



in the place of an insoluble silicate of potash, a very soluble car- 

 bonate of the same base ; the silica thus set free by the dissolving 

 out of the bases, is readily washed away by the rains, together 

 with the insoluble silicate of alumina, forming that well known 

 substance, clay. The proportion of silica and alumina is very near 

 that required to form a soil suitable for cultivation, but the chief 

 excellence consists in the large percentage of potash which it 

 must contain. 



To add anything in this connection with respect to the impor- 

 tance of potash, or any material containing it in large quantities, 

 is, I trust, at the present day, superfluous ; its beneficial efiects 

 have long been seen by all those acquainted with the astonishing 

 effects produced by the contents of the green sand deposites in 

 Monmouth county, if judiciously applied. These effects it is now 

 admitted beyond a possibility of question are owing to the potash 

 contained in the green mineral. 



The usefulness of this feldspar, judging from the results of 

 analysis, promises fully to equal that of the green sand, its pro- 

 portion of potash is in many cases larger, the green sand contain- 

 ing in the average specimens, but six or eight per cent, of alkali, 

 while the feldspar rarely contains less than ten per cent. The 

 decomposition of the feldspar is also quite as rapid and complete 

 as that of the green sand, and its abundance is equal to supplying 

 the largest demand. It is also highly probable from the result 

 obtained by Fownes and others, that these minerals also contain 

 a minute proportion of phosphoric acid, which, although making 

 but a small figure in the analysis, would still be of incalculable 

 benefit in a soil. In the feldspar from the northwest parts of the 

 State, in the vicinity of the beds of mineral phosphates of lime 

 of Sussex county, it is probable that the percentage will be much 

 larger. The phosphate of lime occurs almost uniformly associa- 

 ted with feldspar, and those portions of the vein consisting largely 

 of the latter mineral, still contain much phosphate of lime, and 

 it would seem as if the feldspar fi-om this locality, must be admi- 

 rably calculated to supply the wants of soils deficient in the two 

 important elements, phosphoric acid and potash, these elements 

 occurring as they do, already combined, and requiring only to be 



