4^ On a n£iv futminathig Mercury, 



As to the force of dilated mercury, Mr, Baum^ relates a 



remarkable inftance of it, as follows: 



*' Un alchymifte fe prefenta a Mr. Geoffroy, et I'affura 

 qn'il avoit trouve le moyen de fixer le rnercure par une ope- 

 ration fort fimple. II fit conftruire fix boites rondes en fcr 

 fort epais, qui entroient les unes dans les autres ; la derniere 

 itoit afiTujettie par deux cercles de fer qui fe croifoient ea 

 angles droits. On avoit mis quelques livres de rnercure dans 

 la capacite de la premiere : on mlt cet appareil dans un 

 fourneau alfez rempli de charbon pour faire rougir a. blanc 

 les boites de fer ; mais, lorfque la chaleur eut penetre fuffi- 

 famment le mercure, les bottcs creverent, avec une telle ex- 

 plofion qu'il fe fit un bruit epouvantable : des morccaux de 

 boites furent lances avec tant de rapidite, qu'il y en eut qui 

 palferent au travers de deux planchers ; d'autres firent fur la 

 muraille des effets femblables k ceux des eclats de bombes *." 



Had the alchemifi: propofed to fix water by the fame ap- 

 paratus, the neft of boxes muft, I fuppofe, have likewife been 

 ruptured ; yet it does not follow that the explofion would 

 have been fo tremendous : indeed it is probable that it would 

 not; for, if (as Mr. Kirwan remarked to me) fubftances which 

 have the greateft fpecific gravity have likewife the greateft 

 attraftion of cohefion, the fuppofition that the vapour of 

 mercury exceeds in expanfive force the vapour of water, 

 would agree with a pofition of Sir Ifaac Newton, that thofe 

 f articles recede from one another •with the greatejl force, and 

 are mojt difficultly brought together, which upon contact cohere 



moji flrongly\. 



Section IX. 



Before I attempt to inveftigate the conftituent principles of 

 this powder, it will be proper to defcribe the procefs and ma- 

 nipulations which, from frequent trials, feem to me beft cal- 

 culated to produce it. 



lOO grains, or a greater proportional quantity, of quick- 

 niver (not exceeding 500 grains %) are to be diffolved, with 



heat, 



* CbyTnie expi-imentaleet raifonnee, Tom. 11.^. l^l. Paris, Zvo. 1773, 

 ^ Newton's Optics, p. 372, 4.th edition. LonJon 1730. 

 ^ The rcafon of this limitation is not on account of any danger attend* 



ing 



