3^4 



SALINE EFFLORESCENCE UPON WALLS, &C. 



It was fulphate 

 of magne/ia, 

 very pure. 



face of the ftone'c'tlracy I place the fulleft confidence, exprefsly ftated, that 

 Minder, and not ^^^ taken from the furface of the ftone itfelf, and not fronft 

 from the mortar, the joints, or any part that had been covered with mortar. It 

 exifted there in large quantity, and was difpofed in the form 

 of projefling fpiculse. Upon fubjecling ft to the ufual trials, 

 I found it to be a very pure fulphate of magnefia. In order 

 to afcertain with precifionthe degree of its purity, I prepared 

 a quantity of the fulphate of magnefia, by uniting together its 

 eor>ftitaent parts. This artificial fait, ar>d the lait from York, 

 after being cryftallized, were expofed for fome time to the 

 fame degree of heat, and when all the water of cryftallization 

 appeared to be expelled, equal weights of them were diflblved 

 in equal weights of water: 100 grains of thefe folutions had 

 the muriate of barytes refpeftively added, until no farther 

 precipitation was produced, when it appeared that exaftly 

 the fame weight of barytes was necefiary to faturate each fo» 

 lulion. The portions of precipitated fulphate of barytes were 

 colleded and dried, and when examined by a nice balance, 

 exhibited fcarcely any perceptible difference in weight; they 

 each amounted to 7.9 grains. A firailar procefs being adopted 

 with refpefl to the common Epfora fait of the fliops, the pre- 

 cipitate was found to be 7.35 grains only. Before I quit this 

 uibjecl, Imay remark that another friend, in vifiting the ca- 

 thedral at Tewkefbury, noticed a faline efflorefcence on the 

 infide of fome part of that building ; he collefled a portion of 

 it, intending to give it me for examination; but it was acci- 

 dentally loft. Perhaps fome of your readers, who reiide in 

 that neighbourhood, may be induced to examine it, and tranf- 

 mit the refult to your Journal. I confefs myfelf totally unable 

 to explain the produdion of the fulphate of magnefia on tlie 

 furface of a freeftone, fuch as, I believe, forms the body of 

 York Minfter. 

 Account of a Among the folid concretions which are formed in different 



concretion in the parts of the human body, thofe from the falivary du6ls are og- 

 ^ " ^* cafionally met with. I lately procured one of thefe fub- 

 llances, of which I will give you a brief account. It was a 

 cylinder, pointed at one end, of l>alf an inch in length, and 

 fomewhat more than •— of an inch in diameter j it weighed 

 Jfgr. It was white and fmcolh on the outfide, and its in- 

 ternal fra^fture did not exhibit any marks of regular organiza- 

 tion. To half a grain of the concretion a few dropS'of diluted 



Hittfialic- 



^»i. Wlience 

 came t'he mag- 

 .nefia ? 



