1791' LITERARY INTELLIGENCER. 343 



I do hereby certify, that the above narned Henry Wyn- 

 koop, is a perlon of undoubted good characler, and worthy 

 of credit ; and I do alfo farther teftify, that the plaiier of 

 Paris is much ufed as a manure, in the neighbourhocd of 

 Philadelphia, and that it is genf rally held in high eilima- 

 tion by thofe who have tried it as a manure. 



Samuel Powkll, 

 Prefldent of the Agricultural Society. 

 Philadelphia, June 30, 1 789. 



Letter on the Ufe of Plajier of Paris as a Mcviire, tak- 

 en from a Publication, iutltled, The Am^irican Mu- 

 seum. 



" Having, for four years pall, made ufe of a large quan- 

 tity of plafter of Paris or gypfum as a manure upon a variety 

 of foils, and under diiTereut circumftances, — I beg leave to 

 Jay before you the relult of my experiments, together with 

 fonie obfervations refpeCiing the nature of this foflll. 1' am 

 the more anxious to comply with my duty to the fociety in 

 this refpec):, becauie many of our fcUow-cItizens are loJing 

 the great advantage to be derived from the ufe of this ma- 

 nure ; entertaiaing an opinion, .that it does not in itfelf con- 

 tain any nutriment to plants, but that it a<fis merely as a 

 ftimulus to the foil, by which, although vegetation is for a 

 (hort time rapidly promoted, yet the ground becomes ex- 

 haulled, and is left a dead inert mafs. 



I. In the year 1785, I fowed three acres of light iilng- 

 lafs * foil, containing a little clay, with barley and clover. 

 In the month of April the following year, 1 divided the 

 field into tJiree parts, and ilrewed ilx buihels of French gyp- 

 fum on No. I J the fame qu;intity of the American gypfum, 

 brought from the bay of Fundy, on No. 2 j and left the in- 

 termediate fpace. No. 3, without qny. On cutting the 

 firll crop, that year, little diffeience could be obferved j the 

 fecond crop produced double the quantity of grafs, v/here 

 the gypfum had been put ; and In the I'uccecding year, lhe> 

 difference was Itill greater, in favour of this manure. Early 

 in October 1 787, the clover lay was ploughed ontc, about 

 four inches deep, was fowed \vith rye, and in tl^at rpugh 

 ilate, was harrowed. The rye was of & iuperior* quality, 

 ♦ This }6 a diftin^ion of foil« not known in this countjy. Edit. 



