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XXII. It is ſaid alſo, that on expoſing to the Sun's Rays ſome are wholly dried up; ſo as to be rendered uſeleſs, unleſs macerated and impregnated again with Moiſture: while others by the ſame means become ſofter and more brittle. It is evident that the Humidity is extracted in both theſe Caſes; the Difference is, that the more denſe and compact Stones harden by this drying; whereas the looſer, and thoſe of a leſs firm Texture, become more brittle and ſoft by it.
XXIII. Some of the more brittle Stones there alſo are, which become as it were burning Coals, when put into a Fire, and continue ſo a long time: of this Kind are thoſe about Bena, found
Degrees of Fire, they require to bring them to it, are proportioned to their different Contact of Parts, or Degrees of Coheſion. Such as have leaſt Contacts melt ſooneſt, and for this Reaſon Lead melts more readily than Gold. The different Gravity of the Subſtances has nothing to do in this, ſince it is not according to the Quantity of Matter they contain; but the Number of Points in which the Particles of that Matter touch one another; and for this Reaſon it is that Lead, which is heavier than moſt other Metals, notwithſtanding its ſuperior Quantity of Matter; melts alſo more readily than moſt others.
