Not knowing whether an agricultural Society is still in existence in Pennsylvania, I have chosen to adress this to you to whose Institution no useful discovery is foreign—

I had heard here that the ashes of Pyrites were used as a manure, but I could meet with no satisfactory information on the subject till in a little excursion that I made lately into Flanders I was enabled to see the process & to procure the Samples I enclose.

I observed two persons at some distance from the road employed stiring a heap of earth which emitted smoke but no flame visible at that distance—Leaving my post-chaise & going to them I found that the earth they were burning was a Pyrites Sample No. 1 this was laid upon an earthen floor, in the open air in a bed of about thirty feet long & ten wide and about a foot thick it was reduced into small particles like what I enclose, & when dry contained sufficient Sulphur to burn without any addition.—when the fire was checked in time it formed the red ashes No. 2 which was more valuable than the black No. 3—these other were sifted in a fine sive when they were carried many miles on the backs of asses & used as a manure particularly on grass lands in the proportion of about six bushels to the acre—the corn was also dried in it afore it had been steeped before Sowing & very considerable effect was found from this process. You will observe in this a striking resemblance to the effects of Gypsum & indeed it almost demonstrates that Gypsum derives its fertilizing quality from the Sulphuric acid—this is probably disengaged by slow combustion & retained by the earth either in a combined or uncombined State as the earth may or may not be calcarious or as it may or may not contain vegetable matter reducible to ashes with which it would unite—In writing to the agricultural Society of New-york upon this subject I have suggested to them the Idea of trying diluted Sulphuric & other acids as manures the effect of which would be more instantaneous probably than any combination of them with earth—perhaps too this fertilising quality may not be confined to the mineral acids, if not I have proposed to them a trial of the pyroligneous acid which may by easy process be obtained cheaper than any other.

But the samples enclosed may enable the members of Society to find the earth, which I have reason to think by no means uncommon in the United States—I also send small samples of the Clay used in the fabric of china at Seves to aid the recherches of such of their members, as may wish to make it an object of enquiry—

I have the honor to be, Sir with the highest respect Your most Obt hume Servt