Experimental notes of the mechanical origine or production of fixtness.

CHAP. II. (Book 2)

AND first, it seems precarious to affirm, that in all bodies, or even in all the sensible parts of mixts, Acid and Alcalizate parts are found; there not having been, that I know, any Ex∣perimental Induction made of parti∣culars any thing near numerous enough to make out so great an asser∣tion, and in divers bodies, wherein Experience is vouch'd for the inex∣istence of these Principles, that Inex∣istence is indeed proved not by direct and clear experience, but upon a sup∣position, that such and such effects flow from the operations of the as∣sumed Principles.

Some Spagyrists, when they see Aqua fortis dissolve Filings of Cop∣per, conclude from thence, that the Acid spirits of the Menstruum meet in the metal with an Alcali upon which they work; which is but an unsafe way of arguing, since good Spirit of Urin, which they take to be a volatile Alcali, and which will make a great Conflict with Aqua fortis, will, as I have elsewhere noted, dissolve filings of Copper both readily enough and more genuinly than the Acid liquor is wont to do. So when they see the Magistery of Pearl or Coral, made by dropping oil of Tartar into the solutions of those bodies made with spirit of Vinegar, they ascribe the Precipitation to the fixt Alcali of the Tartar, that mortifies the Acidity of the spirit of Vinegar; whereas the Precipitation would no less insue, if, instead of Alcalizat oil of Tartar, we imploy that highly acid liquor which they call Oleum Sulphuris per Cam∣panam.

I think also it may be doubted, whether those, I reason with, are so certain as they suppose, that at least when they can manifestly discover an Acid, for instance, in a body, the operation of that body upon another, which they judge to abound with an Alcali, must be the effect of a Con∣flict between those two jarring Prin∣ciples, or, if I may so call them, Duel∣lists. For an Acid body may do ma∣ny things, not simply as an acid, but on the score of a Texture or modificati∣on, which endows it with other Qua∣lities as well as Acidity, whose being associated with those other Qualities in some cases may be but accidental to the effect to be produced; since by one or more of these other Qualities the body may act in cases, where Pre∣judice may make a Chymist consider nothing but Acidity. Thus when some Chymists see an acid Menstruum, as Aqua fortis, spirit of Salt, oil of Vi∣triol, &c. dissolve Iron, they present∣ly ascribe the effect to an Acidity of the liquors, whereas well dephlegmed

Urinous Spirits, which they hold to have a great Antipathy to Acids, will, as I have tried in some of them, readi∣ly enough dissolve crude Iron even in the Cold. And on the other side, Mercury will not work on the filings of Iron, though this be so open a metal that even weak liquors will do it; and yet if one should urge, that Quicksilver readily dissolves Gold in Amalgamation, he may expect to be told, according to their Doctrine, that Mercury has in it an occult acid, by which it performs the solution; whereas it seems much more proba∣ble, that Mercury has Corpuscles of such a shape and size as fit them to in∣sinuate themselves into the Commen∣surate Pores they meet with in Gold, but make them unfit to enter readily the Pores of Iron, to which Nature has not made them congruous; as on the other side the saline Corpuscles of Aqua fortis will easily find admission into the Pores of Iron, but not into those of Gold, to which they do not correspond as they do to the others.

And when a knife, whose blade is touched with a Load-stone, cuts bread and takes up filings of Iron, it does neither of them upon the score of Alcali and Acidum, but the one up∣on the visible shape and the stiffness of the blade, and the other upon the latent Contrivance or change of Tex∣ture produced by the operation of the Load-stone in the particles that compose the Steel.

This may perhaps be farther illu∣strated by adding, that when blew Vitriol, being beaten and finely sear∣ced, makes a white pouder, that whiteness is a quality which the pou∣der has not as being of a Vitriolate Nature. For Rock-Crystal or Venice-glass being finely beaten will have the same operation on the Eye, but it proceeds from the transparen∣cy of the body and the minuteness, multitude and confus'd scituation of the Corpuscles that make up the Pouder. And therefore, if other bo∣dies be brought by Comminution in∣to parts endow'd with such Mechani∣cal

affections, as we have named; these aggregates will act upon the or∣gans of Sight as white bodies.