VOL. XXVI.] PHILOSOPHICAL TRANSACTIONS. 429 



top of the water, but it was imfjossible to discover their figure; and then the 

 aquafortis which had been impregnated with tlie red coral was very clear, but 

 when I came to view it through a microscope, I discovered, that there were 

 still a vast number of the long particles floating in it. On placing the said 

 very small particles before a greater magnifier, I discovered such exceedingly 

 slender particles, as almost escaped the sight, and which I suppose were alto- 

 gether invisible before. With this glass I discovered long particles, which not 

 only exceeded the rest in length, but also in thickness, and the ends of which 

 were obtuse ; and having discovered in some few of them three distinct sides, 

 I concluded that they were of a hexangular figure, and consequently that they 

 were particles of saltpetre. 



From these observations, I considered whether all those salt particles, in 

 which I had discovered so many different figures, were not originally of the 

 same shape with those very slender salt particles I discovered on dissolving the 

 coral in the aquafortis, notwithstanding they were a thousand times smaller 

 than they appeared through the microscope; and the difference of their figures 

 may perhaps be only occasioned by the accession or coagulation of other par- 

 ticles, which may be greater or less in one place than in another ; and accord- 

 ingly their figure and size be determined by their nearness to or distance from 

 one another. 



After this I broke off two small pieces of red coral, and placed them on a 

 piece of wood coal, which I made red hot by blowing on it the flame of a wax 

 candle ; and in that condition threw them into a little clean rain water, and 

 presently observed the coral to be dissolved into a fine white substance, and 

 soon after the matter overspread with a scum, which gradually increased in 

 thickness ; and about two hours after, among the infinite number of exceed- 

 ingly small salt particles, I saw some of a larger size coagulated, agreeing with 

 the above salt particles ; in short, one would imagine that the salt particles that 

 were separated from that little piece of coral, and which were coagulated in 

 and upon the water, made altogether a greater body, than even all the parts of 

 the coral itself would amount to. 



Having been informed, that a certain physician made use of coral in his me- 

 dicines; and being myself of opinion, that coral can be of no manner of ser- 

 vice to the bodies of men, I beat some of the finest coral to powder, then 

 mixed it with fair rain water, and caused the mixture to boil ; then put some 

 drops on clean glass plates to evaporate; after which there remained nothing 

 more than by evaporating rain water alone ; so that nothing of the coral was 

 dissolved by the boiling. From whence I conclude, it is impossible that those 

 fixed salts, of which coral is for the most part composed, can possibly be dis- 



