Nitre abounding in the _Nile_, when raised into the Air with the vapors, that exhale continually from this River, there is made out of their mixture, a Dew, that refreshes the Air, makes sickness to cease, and produces all those admirable effects, that make the _AEgyptians_ wish for it so passionately. And the same spirits of Niter, being joyned to the Paste, and to the Mud, raise the one, and augment the weight of the other. That, which Mr. _Buratini_ observes, that at the time of this inundation, the Niter-pits of the neighboring places vomit out liquid Niter, and that one may see issue out of the Earth abundance of Chrystals of Nitre, is alledged to fortify this conjecture; Which is yet more confirm'd by the Fertility, communicated to the Earth by the Mud of this River. For, plants do grow there in such abundance, that they would choak one another, if it were not remedied by throwing Sand upon the Fields; insomuch that the _AEgyptians_ must take as much pains to spread Sand to lessen the fatness of their Land, as other Nations do, to spread dung or other manure upon theirs to increase the fatness. In the _Fourth_ and _Fifth_, the Author undertakes to prove, that all those strange effects cannot be attributed to Rain or Snow, {253} and that the overflowing of the _Nile_ always happens at a certain day. In the _Last_, he alledges some Relations, serving to confirm his Opinion; Which are too long here to insist upon. _DE PRINCIPIIS ET RATIOCINATIONE GEOMETRARUM, Contra Fastum Professorum Geometriae;_ Authore _Thoma Hobbes_. It seems, that this Author is angry with all Geometricians, but himself; yea he plainly saith in the dedication of his Book, that _he invades the whole Nation of them_; and unwilling, it seems, to be call'd to an account for doing so; He will acknowledge no judge of _this_ Age; but is full of hopes, that posterity will pronounce for him. Mean while he ventures to advance this _Dilemma_; _Eorum qui de iisdem rebus mecum aliquid ediderunt, aut solus insanio Ego, aut solus non insanio; tertium enim non est, nisi (quod dicet forte aliquis) insaniamus omnes._ Doubtless, one of these will be granted him. As to the Book it self, he professes, that he doth not write it against _Geometry_, but _Geometers_; and that his design in it is, to shew, That there is no less uncertainty and falsity in the writings of _Mathematicians_, than there is in those of _Naturalists_, _Moralists_, &c., though he judges, that _Physicks_, _Ethicks_, _Politicks_, if they were well demonstrated, would be as certain as the _Mathematicks_.