VOL. XXIII.] PHILOSOPHICAL TRANSACTIONS. 67 



little gold had been already dissolved, and presently observed that the aqua 

 regia began to operate on the copper, as if it had lain in aqua fortis; the 

 gold also cemented with the copper, but in much smaller branches than silver 

 in aqua fortis; and I saw that the gold coagulated so strongly with the copper, 

 that the water about the copper was quite divested of its gold colour ; and 

 after an hour's time, the water was so impregnated with the particles of the 

 copper, that it assumed a green colour, and then one might perceive with the 

 naked eye the gold that lay about the copper. 



Again, I took other aqua regia, that was impregnated with as much gold as 

 it could dissolve, and observed that the coagulated salt particles were of an ex- 

 ceedingly fine gold colour, being composed of extremely small particles, and the 

 corners or angles were very regular. I placed these salts before my microscope, 

 and they seemed of such a figure and texture, as if it had been a piece of gold 

 newly taken out of the mines. 



Now, in order to expose to view the coagulated salt particles in their first 

 coalition, I put the said impregnated water on a clean glass, and then caused 

 part of it to run off the glass again, that the remainder might lie as thin as 

 possibly in the glass without touching it, imagining that the said water lying 

 thus thin, the salt particles might coagulate the more regularly; and I observed 

 afterwards that most of those salt particles were hexangular, though so ex- 

 ceedingly small that they almost escaped the sight, and many of them were re- 

 gular hexangles, as represented; see fig. 12, abc ; fig. 13, def; fig. 14, ghi ; 

 fig. 15, KLM ; and fig. l6, nop. Most of these figures were as transparent as 

 glass, and all of them were surrounded with a liquid matter, somewhat of a 

 gold colour, which did not exhale, though the weather was very warm and dry. 



I saw also a vast number of particles so exceedingly small, that their figure 

 was not distinguishable, though I believed them to be salt particles likewise; the 

 rather, because I could not observe any of these small salts lying near the 

 aforesaid large ones, which, through the sympathetic inclination of homogene- 

 ous bodies, I concluded to be composed of a congeries of such small ones. I 

 saw also other particles that were not pellucid at all, which I suppose were 

 surrounded with so many gold particles, that they were not only of an irregular 

 figure, but also opaque. Many of these salt figures were more protuberant in 

 the circumference than in the middle, and had also several rings, which still 

 the more confirms me in the opinion of those secret inclinations of like bodies ; 

 and thus in their increase they preserve the same shape which the single salts 

 had put on at their first coagulation. 



Into such water I also put a little piece of copper, and observed that imme- 

 diately the gold had partly united itself with the copper, but the aqua regia had 



VOL. V. I 



