or Sulphate of Irojt, as a Manure. 57 



of one-sixteenth of a grain, it is as harmless as a glass of 

 wine; and fiirthefj in that dose is a remedy tor inveterate 

 agues. 



From these considerations I conclude, that there is no 

 admissible contradictory evidence to the testimonies for the 

 fertilizing effect of sulphate of iron, unless by such con- 

 travening evidence the quantify stated to be vised exceed 

 /iftv hushels per acre; it being an established fact, that in 

 certain proportions this metallic salt is a poison to plants. 



This discovery of Mr. Willaume will, I think, give new 

 light, so as to explain fully the rationale of the improve- 

 ment of land by the burnt earth and ashes from paring and 

 burning. It is usual to account for the etfects of this pro- 

 cess, by referring to supposed alkaline or ot'ner salts ; bul 

 of these there is no evidence; nay, on trial I have not de- 

 tected them, or at least not in any efficient quantity ; but 

 tliis I know, that such earth and ashes contain oxide of 

 iron, and as I suspect of manganese ; which from the ana- 

 lysis, and the effect of salt of pe.it, must now be admitted 

 into the class of manures. This very communication of 

 Mr. Willaume affords evidence of the truth of this conjec- 

 ture; for the ashes of the peat whicb. affords the salt " have 

 been long known as a man\ire, and the demand is on the in- 

 crease :" of course, these ashes contain an unusual quantity 

 of oxide of iron. A consequence of this reasoning is, that 

 the burnt enrth of soils will, cceteris paribus, fertilize in pro- 

 portion to the oxide of iron it contains. Accordinglv, the 

 ashes of the peat, savs Mr. Willaume, have a svu-prising 

 effect; they " will double or treble a crop of any new sown 

 .grass, such as trefoil, &c.": they are .so beneficial, that, in 

 5j)itc of the cxpencc, they are carried in bags by higglers to 

 great distances. It would be extending this paper beyond 

 the proposed limits, to reason at greater length, and to make 

 a further induction of facts ; therefore I will close with as- 

 serting, that the more I contemplate the facts in .Mr. WiU 

 laun)e's letter, the more evidence I perceive for the truth, 

 that metallic salts and metallic oxides in general, and s.alts 

 and oxides of iron in particular, are manures, if applied iu 

 proper doses. 



I do not think it is within the design of this ]);tper to 

 make observations on the answers to the 'Jd, 3d, -itli, .5th, 

 and ()th queries, except once h)r all, desiring that it may be 

 understood that I consider the salt of peat, and the ashes of 

 peit, as operating in promoting vegetation analogous to 

 seasoning, rir condiments, taken with the food of animals; 

 tljat ij, analagous to raustard, cinnamon, ginger, Sec. which 



are 



