56 On the Use of Green Vitriol of Iran, 



a very copious greenish sediment ; and the same effect en- 

 sued with caustic volatile alkali. 



11. The solution (2) with oxalic acid, gave instantly a 

 very turbid blucish green precipitation. 



The preceding experiments manifested that the peat salt 

 consists ot" sulphate of iron, vulgarly calU'.d green vitriol of 

 iron, mixed with a very minute proportion of siliceous 

 earth, and of lime imited cither to sulplmric acid or to car- 

 bonic acid. But the presence of the earths mao;nesia and 

 argil ; the uncombir.e^l alkalis ; the uncon}bined acids ; 

 are by these experiments excluded. In short, the salt of 

 peat is almost pure sulj^hale of iron. 



REMARKS. 



1. The salt of peat js, I apprehend, deposited bv evapo- 

 rations which run over the moors where it is found ; and 

 hence I should expect many of such waters to be strongly 

 impregnated v/ith it, and in many parts the soil to be tingecj 

 red and yellow by ochre. \zxy likely* on inquiry much 

 iron pvrites will be found on or near the moors. 



2. The quantity spread on land is said to be fifty bushels 

 per acre, which 1 estimate at 2,250 pounds avoirdupolsc ; 

 thjs will give near seven ounces and a half per square yard, 

 If a larger quantity be applied, it is observed it will prove 

 extremelv deleterious. Tliis is true also of every other ma- 

 nure, such as lime, alkaline salts, marine salt j nav, of the 

 dung of animals ; for if thev be used in certain quantities 

 they poison plants instead of promoting their growth. This 

 is equally true in the animal kingdom; for there is not an 

 article taken as food, or as seasoning, which is not a poison 

 if taken in certain quantities. A human creature may b(f 

 poisoned or alimented by beef or pudding, according to the 

 quantitv of them taken into the stomach. Ife mav be poi- 

 soned or have digestion greatly assisted bv salt or pepper,* 

 according to their quantity. In brief, the vulgar notion of 

 the term pois-m is erroneous : for by it is conceived that 

 substances so called are in their nature positively destruc- 

 tive of life; but the truth is, that the most virulent poisons 

 are, in all reason aqd fact, only deleterious according to the 

 quantity applied. White arsenic, swallowed in the quantity 

 often grains or less, \yill destroy life; but in the quantity 



* " This is,'' says Mr. Wiilaumc, " exactly the f.ict. This sul- 

 phate of iron, the salt <>f peat, during the heat of the sunamcr is fre- 

 quently found in a cry^t.iirizcil state, very white, and crackling under 

 the feet; but is deliquescent in that form, and turns to its former dark 

 polour when the air bccoine.s moist." — Note ky Mr. J. IV. Willaxime. 



Of 



