550 PHILOSOPHICAL TRANSACTIONS. [aNNO 17 10, 



many rough diamonds ; I separated the sih'er, and melted it, and then poured ' 

 fresh aquafortis upon it, that I might once more discover the crystalline or 

 adamantine figures of it ; but in vain, for I could only now and then meet 

 with one crystalline figure of the shape of a diamond. 



For further satisfaction therefore, I took a piece of silver, being part of a 

 Portuguese piece-of-eight, many years ago, and threw it into aquafortis, when 

 the-water was soon tinged with a green colour; from whence I inferred there 

 was a great deal of copper in it. After the silver had lain eleven days in the 

 aquafortis, I saw a great many long particles coagulated in it, which I judged 

 to be hexangular, and as clear as crystal. I poured off this water very gently, 

 that the long particles discovered by my microscope might remain in the glass; 

 and then I poured upon them 4 times as much rain water as there had been 

 aquafortis before in the same place, that the salt particles still in the glass 

 might go over to the water : I then drew this water off again, and poured on 

 fresh ; and then viewing the particles through my microscope, observed 

 them in great numbers sticking to the sides of the glass ; but found, that those 

 which were as clear as crystal before, had lost a great deal of their tran- 

 sparency, and assumed a pale red colour, which gradually became redder ; and 

 after some hours the colour was so deep, that it appeared blackish, having no 

 manner of transparency ; and where the particles lay thick together, they ap- 

 peared to the naked eye like a whitish matter. 



I likewise poured off very gently the aquafortis from another glass, in which 

 were a great number of these long crystalline particles, and then turned the 

 glass upside down, that the little water remaining in it might be drained out ; 

 by which means a great number of the said particles remained sticking to the 

 sides of the glass ; and as I had poured no rain water upon them, they pre- 

 served their transparency. 



As often as I dissolved the silver in aquafortis, I could not discover any 

 diamond-like figures worth speaking of, but only several very long particles, 

 such as are represented, pi. 13, fig. ], 2, 3, 4, 5, on which I suspected the 

 aquafortis was not good; but was informed it was the same tliat was sold, not 

 only to the gold and silversmiths, but also to the silk dyers. However, having 

 suffered formerly, in endeavouring to separate gold from silver, by using aqua- 

 fortis that had been drawn off from foul copperas and salt, (that it might be 

 sold the cheaper,) I procured from a goldsmith some of his aquafortis, in 

 which I dissolved not only my own silver, but also some that had been 

 coined in England, which proved to my satisfaction; for I discovered therein 

 as many particles of the form of bright diamonds, as in any of my foregoing 

 observations ; pnly with this difference, that the crystalline particles of the 



