190 OF TltE ANHYDROUS SULPHATE OF LIME. 



ciilty of taking out the fugar after its drainage. A fecond h, 

 that the holes in their bottom are too fmall, which renders 

 them liable to be obitructed, and the procefs to be greatly 

 retarded. 



(To be concluded in our next*) 



VIII. 



Defer iption of the Crystalline Forms of the Anhydrous Sulphate of 

 Lime, mthjbtne Obfervations on this Subjlance. By M. Lc 

 Comte de Bournon, Member of the Royal and Linnaan 

 Societies of London. Tranjlated from the Original, commu- 

 nicated by the Author *. 



L U n?ain?ng°no me GrYPSOM, or the fulphate of lime deprived of water, is a 

 water is a new new object in mineralogy : fcarcely has the fcience as yet 

 objea in mine- ca ft a glance upon this fubftance, and none of its cryftalline 

 forms have hitherto been determined. Having had opportu- 

 nities of examining fome of thefe forms, and at the fame time 

 of comparing a number of fpecimens of this fubftance, pro- 

 cured from different countries, I felt myfelf induced to lay 

 before the Public my obfervations upon this fubject, thinking 

 they might contribute to throw fome light upon the nature of 

 feveral (tones, with which we are not yet perfectly ac* 

 quainted. 

 Its primitive The primitive form of this fubftance, which has beendelig- 



prifm with reft- na ted by the name of Anhydrous Sulphate of Lime by the 

 angular bafes. Abbe Hauy, is a rectangular paralelopiped, as had been pre- 

 sumed by this able mineralogift ; but it does not appear that 

 this paralelopiped can be the perfect cube, as is indicated by 

 the habitual form of the cryftals, which when molt fimple, is 

 always a right prifm with rectangular bafes, having two op- 

 pofite fides broader than the two others (Fig. 1, Plate XL), 

 and feems equally to be indicated by the circumftances which 

 Eafily divided, accompany this form. The mechanical divifion is very eafy 

 upon all the faces of this cryftal ; but the longitudinal ftraight 

 faces prefent, in this refpect, a little more refinance than the 

 others. 



And a fterwards revifed by him. 



The 



