or Sulphate of Iron, as a Manure. 61 



Ye^alive to the effects of various stimulating articles, such 

 Us camphor, &c. upon vegetables ; and on the absorption 

 of certain powerful n)incral substances into the organic sys-» 

 tern of vegetables. In numerous instances I have subjected 

 the stems and leaves of plants, young and old, large and 

 small, to the influence of the sulphates of iron and copper. 

 I have found that both of these metallic salts are very 

 greedily absorbed by vegetables, insomuch that I have de- 

 tected the presence of iron in the vessels of a branch of mul- 

 berry, at the height of five or six feet above the place of im- 

 mersion, in a solution of the sulphate of this metal. A full 

 account of my experiments I design to communicate to the 

 public in two memoirs. Permit me to observe in the mean- 

 while, that the sulphate of iron applied to vegetables in the 

 manner I have mentioned " is only (to use your own words) 

 a poison, like almost every thing else, from the over-dose." 

 In several of my experiments the branches of vegetables that 

 were placed in vessels containing solutions of the sulphate 

 of iron and copper, lived longer and exhibited more sitrns 

 of vigour than similar branches that were placed in equal 

 quantities of simple water. It is true, that in many other 

 experiments these metallic salts proved fatal to my plants; 

 but this was when I employed too large a dose. In like 

 manner I had found, several years ago *, that camphor, 

 by greatly stimulating, often kills vegetables ; and yet, when 

 properly dosed, this is a very wholesome stimulant to plants. 

 I had also found that large doses of nitre (which is unques- 

 tionably a powerful stimulant, both with respect to animals 

 and vegetables) produce an appearance like genuine gan- 

 grene in the leaves of vegetables ; and yet it is certain that 

 nitre, when it is judiciously dosed, maybe made to greatly 

 assist the healthy vegetation of plants. 



Excuse the liberty I have taken in troubling you with 

 these few loose hints, and permit me to subscribe myself, 

 Sir, your very humble and obedient servant, kc. 

 To Dr. Pearson. Bknmamin Smith Barton. 



4. Sulphate of Iron in the Peat of Russia, found hy 

 Professor R'lhhison. 



Something else l>e?i(Us vegetable matter is necessary to 

 form peat or black mos> of the moors. The smell of burn- 

 ing peat is difleicnt from that of vegetable matter. Peat 

 ashes, says the professor, always contain a very great pro- 



" See TraO'.aaiorjs of the American Plii!o?opliicaJ Society, vol. iv. 

 no. 27. 



portion 



