and therefore they also, as being round, must be also incorruptible; and likewise in the remainders, which environ these eight lesser Spheres, a man may understand that there are others: so that in the end, resolving the whole Die into innumerable balls, it must necessarily be granted incorruptible. And the same discourse and resolution may be made in all other figures.
Salv.Your method in making the conclusion, for if v. g. a round Chrystal were, by reason of its figure, incorruptible; namely, received from thence a faculy of resisting all internal and external alterations, we should not find, that the joyning to it other Chrystal, and reducing it v. g. into a Cube, would any whit alter it within, or without; so as that it would thereupon become lesse apt to resist the new ambient, made of the same matter, than it was to resist the other, of a matter different; and especially, if it be true, that corruption is generated by contraries, as Aristotle saith; and with what can you enclose that ball of Crystal, that is lesse contrary to it, than Crystal it self? But we are not aware how time flies away; and it will be too late before we come to an end of our dispute, if we should make so long discourses, upon every particular; besides our memories are so confounded in the multiplicity of notions, that I can very hardly recal to mind the Propotsiions, which I proposed in order to Simplicius, for our consideration.
Simpl.I very well remember them: And as to this particular question of the montuosity of the Moon, there yet remains unanswered that which I have alledged, as the cause, (and which may very well serve for a solution) of that Phænomenon, saying, that it is an illusion proceeding from the parts of the Moon, being unequally opacous, and perspicuous.
Sagr.Even now, when Simplicius ascribed the apparent Protnberancies or unevennesses of the Moon (according to the opinion of a certain Peripatetick his friend) to the diversly opacous, and perspicuous parts of the said Moon,Mother of Pearl accommodated to imitate the apparent unevennesses of the Moons surface. conformable to which the like illusions are seen in Crystal, and Jems of divers kinds, I bethought my self of a matter much more commodious for the representing such effects; which is such, that I verily believe, that that Philosopher would give any price for it; and it is the mother of Pearl, which is wrought into divers figures, and though it be brought to an extreme evennesse, yet it seemeth to the eye in several parts, so variously hollow and knotty, that we can scarce credit our feeling of their evennesse.
Salv.This invention is truly ingenious; and that which hath not been done already, may be done in time to come; and if there have been produced other Jems, and Crystals, which have nothing to do with the illusions of the mother of Pearl, these maybe
