56 PHILOSOPHICAL TRANSACTIONS. [aNNO 1703. 



seconds of a minute, such a coagulation of branched particles (which even 

 through a good microscope M^ere invisible) arising from a seeming clear dia- 

 phanous and hquid matter. 



From these coagulated small silver particles, I was led to consider the rich 

 silver stone, brought in small fragments from the West Indies ; which has its 

 particles coagulated in just such branches as appeared in the water by the 

 microscope ; from whence I am the more fully confirmed in my hypothesis, 

 that when the parts of that stone were a fluid substance, the silver particles 

 were also mixed with them ; and when the stone consolidated, the silver also 

 was coagulated in branches, just as we see it now lying in the stone, with 

 which it is surrounded, and as it were imprisoned ; from whence several have 

 imagined that in process of time the silver grew in the said stone. 



I took a piece of gold, and threw it into a proportionable quantity of aqua 

 regia; in the dissolving of which 1 saw air-bubbles ascending in like manner as 

 I said before of the silver. A little time after 1 took some of the aqua regia 

 thus impregnated, and laid it on a clean glass, to observe, after the mingled 

 salts were coagulated, what gold particles I could discover in them. When it 

 was fair warm weather, the salts were for the most part coagulated, but in such 

 a variety of figures, that they were hardly to be accounted for; sometimes re- 

 presenting an exact hexangular figure, by and by the very same figures were no 

 less irregular; the occasion of which was, as I conceive, because the coalescence 

 of new particles was not equal on every side ; but that which was the most 

 remarkable was, that upon these salt particles, that were as transparent as 

 yellow crystal, there lay other salt particles of a fine gold colour, and some- 

 times they appeared as if these fine gold coloured salts were inclosed in the 

 other salt particles, which caused a very agreeable phenomenon ; but when the 

 weather grew damp and moist, all the crystal salts were dissolved, and the gold- 

 coloured salts were mixed with the common particles. 



I took another little piece of gold, that had been wrought by a goldsmith 

 and having beaten it very thin, I put it into the same glass, where my other 

 gold had been, with aqua regia ; and observed that a white substance was 

 separated from it, and subsided in the bottom of the glass ; for as aqua fortis 

 dissolves silver, while the gold escapes untouched, so aqua regia dissolves gold, 

 without affecting the silver at all. Hence I infer, that the gold was alloyed 

 with some silver, which was the white substance, separated as before said. 

 The piece of gold that lay in the aqua regia would not unite with it ; 

 whence I concluded that there was too much gold, and too little water, for I 

 had made the glass so hot that I could not bear it with my hand. 



I took also a small piece of copper, and put it into aqua regia, where a 



