FERTILISING PROPERTIES OF THE GREEN SAND. 307 



it a certain fertilising value, as an application to the 

 poor thin sandy soils of which I have spoken, as being- 

 covered so extensively with orchards of the short-lived 

 peach-tree. Loose beds of green sand, of an exceedingly 

 pure kind that is to say, consisting of green granules 

 intermixed with grains of quartz, in which the former 

 abound in a far greater degree than has, I believe, ever 

 been met with in our English green sands occur in 

 New Jersey. From these beds the fine loose sand is 

 dug up, and carted to considerable distances to be spread 

 upon the land. Its efficacy is very generally acknow 

 ledged, but few accurate results of experiments have been 

 published, from which its precise value can be estimated. 



Among the persons who interest themselves with 

 scientific agriculture at Philadelphia, I conversed upon 

 this matter with Dr Elhvyn, the President of the Local 

 Agricultural Society ; with Professor Rogers, the suc 

 cessor of Dr Hare in the chemical chair of the Medical 

 College of Philadelphia, and with Dr Emerson, who has 

 edited some valuable agricultural works ; and I found 

 them universally of opinion, that i\& potash contained in 

 the green grains was the cause of the fertilising action 

 of the sand, to which it gave the green colour. In the 

 pure green grains, this potash amounted by analysis to 

 8 per cent or upwards, and ascribing, after Liebig, a pre 

 ponderating influence to this ingredient of plants and 

 soils, the discovery of this potash was held by these 

 gentlemen to be a satisfactory explanation also of the 

 good effects of the green sand, when applied to the 

 naturally poor arenaceous soils. 



Without refusing a certain virtue to the potash, which 

 green sand and other rocky substances may contain, the 

 following facts satisfied me that the matter in question, 

 so far from being cleared up, was still open to investiga 

 tion. Thus it was acknowledged, first that all samples 

 of green sand, that beds from every locality, did not pro- 



