to perform such and such Effects; as upon the account of the particular texture of that and the other Ingredients, associated after a determinate Manner into one Concrete (though possibly such a proportion of that ingredient may be more convenient than an other for the constituting of such a body.) Thus in a clock the hand is mov'd upon the dyal, the bell is struck, and the other actions belonging to the engine are perform'd, not because the Wheeles are of brass or iron, or part of one metal and part of another, or because the weights are of Lead, but by Vertue of the size, shape, bigness, and co-aptation of the several parts; which would performe the same things though the wheels were of Silver, or Lead, or Wood, and the Weights of Stone or Clay; provided the Fabrick or Contrivance of the engine were the same: though it be not to be deny'd, that Brasse and Steel are more convenient materials to make clock-wheels of than Lead, or Wood. And to let you see, _Eleutherius_, that 'tis sometimes at least, upon the Texture of the small parts of a body, and not alwaies upon the presence, or recesse, or increase, or Decrement of any one of its Principle, that it may lose some such Qualities, and acquire some such others as are thought very strongly inherent to the bodies they Reside in. [Errata: in;] I will add to what may from my past discourse be refer'd to this purpose, this Notable Example, from my Own experience; That Lead may without any additament, and only by various applications of the Fire, lose its colour, and acquire sometimes a gray, sometimes a yellowish, sometimes a red, sometimes an _amethihstine_ [Transcriber's Note: amethistine] colour; and after having past through these, and perhaps divers others, again recover its leaden colour, and be made a bright body. That also this Lead, which is so flexible a metal, may be made as brittle as Glasse, and presently be brought to be again flexible and Malleable as before. And besides, that the same lead, which I find by _Microscopes_ to be one of the most opacous bodies in the World, may be reduced to a fine transparent glasse; whence yet it may returne to an opacous Nature again; and all this, as I said, without the addition of any extraneous body, and meerly by the manner and Method of exposing it to the Fire. But (sayes _Carneades_) after having already put you to so prolix a trouble, it is time for me to relieve you with a promise of putting speedily a period to it; And to make good that promise, I shall from all that I have hitherto discoursed with you, deduce but this one proposition by way of Corollary. [_That it may as yet be doubted, whether or no there be any determinate Number of Elements; Or, if you please, whether or no all compound bodies, do consist of the same number of Elementary ingredients or material Principles._]