242 USE 0F GREEN VITRIOL 



to communicate to the public in two memoirs. Permit me 

 to obferve, in the meanwhile, that the fulphate of iron, applied 

 to vegetables in the manner I have mentioned, " is only (to 

 ufe your own words) a poifon, like almoft every thing elfe, 

 from the over-dofe." In fever al of 'my experiments, the branches 

 of vegetables that were placed in vejjels containing folutions of 

 fulphate of iron and copper, lived longer and exhibited more 

 figns of vigour, than fimilar branches that ivere placed in equal 

 quantities of fvnple water. It is true, that, in many other ex- 

 periments, thefe metallic falts proved fatal to my plants ; but 

 ' y this was when I employed too large a dofe. In like manner 

 I had found feveral years ago *, that camphire, by greatly 

 Simulating, often kills vegetables ; and yet, when properly 

 dofed, this is a very wholefome ilimulant to plants. I had 

 alfo found, that large dofes of nitre (which is unqueftionably 

 a powerful Ilimulant both with reipedt to animals and vege- 

 tables) produce an appearance like genuine gangrene in the 

 leaves of vegetables : and yet it is certain that nitre, when 

 it is judicioufly dofed, may be made to greatly affift the healthy 

 vegetation of plants. 



Excufe the liberty I have taken in troubling you with thefe 

 few loofe hints, and permit me to fubfcribe myfelf, 



Sir, your very humble and obedient Servant, &c. 



Benjamin Smith Barton. 



4. Sulphate of Iron in the Peat of Tiujfia, found by Profejfor 



Robifon. 



Sulphate of iron Something elfe befides vegetable matter is necefiary to form 



exifts in Ruffian p eat of ^Jack mofs of the moors. The fmell of burning peat 



is different from that of vegetable matter. Peat afhes, fays 



the Profefibr, always contain a very great proportion of iron ; 



he has feen three places in Ruffia where there is fuperficial 



peat mofs, and in all of them the vitriol is fo abundant as to 



effiorefce. In particular, on a moor near St. Peterlburgh, the 



clods (hew the vitriol (fulphate of iron) every morning when 



the dew has evaporated. According to this learned Profeflbr's 



obfervation, the fulphate of iron in pit coal may be accounted 



for in the following manner : " peat mofles form very regular 



* See Trnnfa&ions of the American Philofophical Society, 

 Vol. IV. No. xxvii. 



flrata, 



