Se<fl. VII. Agriculture and Vegetation. 35 



with acids. This reafoning is put beyond 

 all doubt by the following experiment. 



Exp. 1 6. I took one pound of good rich 

 mould, and mixed with it one drachm of fait 

 of fteel; put it into a pot, and fowed feme 

 barley in it in the beginning of May. Some 

 of them (hot up about an inch, looked very 

 ill-coloured and fickly, and then died; 

 while other grains in another pot, filled 

 with the fame earth, throve very well. 



THUS a very fmall quantity of iron, 

 diffolved by the vitriolic acid, rendered a 

 great quantity of rich eartii unfruitful, and 

 therefore ought to be looked on as the ve- 

 getable poifon of till. If this poifon can 

 admit of a cure, I imagine it is only to be 

 found in lime or marl, which will attract 

 the acids from the iron, and make it, at leaft 

 in a great meafure, indiflblvable in water. 



THOUGH the admixture of iron with 



the foil may be a very general caufe of un- 



D 2 fruit- 



