368 PHILOSOPHICAL TRANSACTIONS. ("anNO 170/. 



though they swim in salt water, and always receive the same into their stomach 

 and bowels; yet none of the salts mix with their blood, but coagulate in such 

 a manner in the stomach and guts, that they assume the figure of diamonds, 

 and pass through their bodies with the excrements. In short, we may con- 

 clude, that pearls are useless as a medicine ; and I must own that I have the 

 same opinion of gold too, though I have often heard it mightily cried up by 

 some people, as also silver by others. 



rfttNow, since pearls are produced as it were accidentally in the shells of oysters, 

 there is no doubt but that they have one and the same salt particles, and con- 

 sequently that their operations are uniform. For my farther satisfaction, I took 

 some very old oyster shells, that were quite dry with age, and found that they 

 were composed of a multitude of exceedingly thin laminae. Some of the inner 

 fine particles being burnt and thrown into water, &c. produced a scum of co- 

 agulated salt particles, just like the pearls when treated the same way. And 

 the like happened by boiling the pounded shells, and evaporating the water, as 

 when the pearl powder was boiled, &c. 



Concerning the Particles of Silver dissolved in Aquafortis, &c. By Signor 

 Antonio Magliabechi, N° 311, p. 2425. 



I communicated to you, some months ago, my opinion concerning diamonds, 

 viz. that they do not grow larger by lying in the earth, but that their magni- 

 tude and figure is assumed at once, and at the very time of the coagulation or 

 coalescence of the particles which compose them. I was the more confirmed 

 in this, by putting silver into a glass tube, about the thickness of my finger, 

 and length of my hand; and poured on it as much aquafortis as was sufficient 

 to dissolve it. I put this glass tube, which was a third part filled with aqua- 

 fortis impregnated with silver, into a pot filled with sand, and placed it almost 

 horizontally, and so as that it might not stir any way, in hopes that I might 

 the better observe, after a few days, the coagulating particles, subsiding to the 

 bottom, all along the length of the tube. Viewing this glass tube with a 

 microscope, I observed divers small long particles coagulated, which I judged 

 to be particles of salt petre ; for as I turned the tube a little before my eyes, 

 and as gently as I could, I put those particles into a little motion, and thereby 

 at once discovered three sides of them, which I imagined to be the half of 

 those bodies, and consequently that their figure was hexangular ; they appeared 

 also as clear as crystal. I saw a few long particles, some of which were in- 

 clining to a red, others to a peach colour. I further observed exceedingly small 

 particles, that had the figure of polished pointed diamonds ; others were co- 

 agulated more irregularly. 



