OiiCdlcarious and GypfioUa Eay-ths. o/ 



more accurate anal) fis of tlicm than m;- imperfeft knowledge 

 of chyniiflry has permlited me to make. I mixed a quart of 

 pulverized Gypfitm with an equal quantity of v/ood afhes, and 

 leached it with boiling water; as it evaporated, it depofited a 

 lak of a dirty brown colour^ the cryflals imperfeftly formed. 

 It was faturated with a folution of pptafiies, and, when Cf^ld, 

 fnot into regular cryftals, which were fliarp at the point, and 

 broad at the bafe, not unlike to the blade of a fmall fword. 

 Though this is not the form of vitriolated tartar (which is the 

 ialt produced from the vitriolic acid and a vegetable alkali) 

 the difference may have ar fen from a metalic gas, which 

 might have been detached from the glazing of the vefTel 

 in which it was boiled. This I the rather imagine, as I 

 'afterwards obtained vitriolated tartar by fuiTering the liquor to 

 evaporate flo\yly in the open air, to which it was expofed for 

 three weeks. Pulverized lime/lone, treated in the fame v/ay, 

 gave a irteutral fait, confifting of a great number of long thin 

 needles, equally thick at either extremity. As this is the fait 

 produced by combining fixed air with the vegetable alkali, it 

 proves that the efTential fait of limeftone is fixed aii\_ which 

 Jliews a difference between that and Gypfum that may" in cer- 

 tain circuiiiftances be of confequence, particularly in foils that 

 abound with a vitriolic acid, as many boggy foils do ; in 

 which cafe the limeftone fhould be preferred, fince the elefiive 

 attraQion between fixed air and C altar icus earth is weaker 



