[ 95 ]
XXXIX. The different Sorts alſo vary from one another in Colour, Compactneſs, and Gravity.
XL. As to their Colour, there is a black Kind found on the Sicilian Shores, which is compact and weighty, and ſomething reſembles that kind of the Pyrites called the Molaris: for there is a natural Pumice of this Texture, heavy and compact; and this is of more Value and more uſeful than many of the others; this Kind from the Shores is a better Abſtergent than the light white Kind: But the moſt abſtergent of all others, is that from the Sea itſelf.
different Species of the Pumice, are what may be obſerved in a greater or leſſer degree in the various Kinds we now have brought from Germany, the East Indies, and the burning Mountains; and the Author appears to have been very well acquainted with them: His aſſigning a greater Degree of the abſtergent Quality to that from the Shores than that from the burning Mountains; and a greater than even in that, to those of the Sea, is probably very juſt, though not now regarded, as the Sea Salt incorporated in the Maſs of thoſe, muſt add much to this Quality.
The Author having now gone through the Nature of the Pumices, returns to the Conſideration of thoſe Stones he was before deſcribing, and from the Hiſtory of which he had looked on this as a Digreſſion. The Stones here treated of, are what he has before named among the Gem Kind, as I have already obſerved in regard to the Senſe of the Word σφραγίδιον; ſome of the Species of which he
