268 PHILOSOPHICAL TRANSACTIONS. [aNNO 1705. 



I could perceive a great number of salt particles, whose basis was an exact square, 

 all the four sides of which ascended pyramidically; the superficies of others, 

 which could be but just perceived by the help of a good microscope, was a very 

 small square, resembling the coagulations of common salt; and as this in 

 moist weather becomes liquid, so also did these ; but as soon as it was fair 

 and dry weather again, the watery parts exhaled, and the salts resumed their 

 former figure; I saw likewise among them some particles that were common salt. 



Now, I doubt not that many of these pumice-stones are found in the sea ; 

 for having viewed several of them, they appeared not to have any sharp angles ; 

 and, among the rest, there was one of an oval figure, and as large as a man's fist, 

 which when thrown into the water I saw it float with the half of its bulk above 

 the surface of the water; from whence I concluded, that by its long driving in 

 the water, the angles of such a stone were so worn off, that instead of having 

 sharp and uneven points, they were grown to be blunt and smooth. The same 

 stone being laid on the fire, I could perceive a smoky matter evaporating from it. 



This last experiment induced me to take some of the little pieces of the 

 stone, in order to keep together, as much as it was possible, the matter which 

 was exhaled from them ; and then I perceived that the first matter which was 

 driven off, was as a very bright vapour ; but the next, which was forced out by 

 a yet stronger fire, was not near so bright, and was charged with immense 

 numbers of exceedingly small particles, which, by reason of their weight, sunk 

 to the bottom, after which that vapour became clear: there was also drawn off 

 from the same stone a little matter, which I took to be sulphur. 



I have before now heard, that the sponges which are found in the sea did 

 grow upon the rocks; which however I could hardly conceive, believing that the 

 solid rocks could not produce such a substance; but when I came to be informed 

 that there are whole rocks in the sea composed of pumice-stone, it is easy to 

 imagine that they may produce such a matter as we call sponge. 



Having one of these sponges, in which I found a little hardness, from which 

 I supposed the sponge received its first grawth. Having opened that part of 

 the sponge, I took out of it a little shell, and some very small stones : the shell 

 was of a particular figure, and such as is not to be found on the sea shores. 

 Then examining several other sponges, I took various small shells, horns, and 

 stones out of them, and among the rest, one shell larger than any of those that 

 I had seen before; from whence I concluded, that the storms, by putting the 

 sea into an extraordinary motion, in or about those places where sponges grow 

 upon the rocks, had raised from the ground these small shells and stones, and 

 thrown them into the sponges while growing; the rather, because these little 

 shells and stones were not only surrounded in such a manner by the sponges, as 

 to impress their own figures in them, but even the parts of the sponges had 



