Sea. is-

Of Metals.

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cíes, and therefore to be cold anddrying,

Preparations of Silver.

Caufticum Lunare, the LunarCaußic.

' Diflblve in a Phial any quan-' tky of Silver, with three times' as much Spirit of Nitre: Set the« Phial in a Sand-Heat, and evapo-' rate about two thirds of the Moif-' ture; pour the reft, while it is« hot, into a good Crucible, that■ mall be large, by reafon of the« Ebullition it will make. Place it' over a gentle Fire, and let it alone« till the boiling Matter links quietly« to the bottom of the Crucible,* Then increafe the Fire till it comes« to be like Oil, and pour it out into' an Iron Mould, a little oil'd and' heated, and it will prefently har-" den. Itmuft be kept dole ftopp'd,« elfe the Air will run it, and de-« ftroy its Efficacy ; but fo, it will' laft forever.'

This Stone may be made ofCof-f er, but it will not keep fo well ;becaufe that Metal being m&re po-rous, fooner admits the Air into it :There are many other Preparationsof Silver, but they are of no ufe,unleís for Amufement, and to makea fhew to no purpofe.

613. Ferrum, Iron. If ourregard of the Planets was tobe pro-portioned to the Medicinal Efficaciesof thofe Metals which the Chyrmftshave imagined them to influence ;Mars ought to be more in ourcfteem than the Sun or Moot, asIron is vafliy preferable in Medicineto either Gold or Siher, tho fup-pos'd to be under the Dominion ofthofe great Luminaries.

Naturalifts abundantly inform usconcerning the produftion of thisMetal; and Phyñcal Writers fuffi-ciently prove how much it is pre-ferable for 3II Medicinal Purpofesto Steel, which is only a more har-den'd compaif. Iron, made fo byArt j whereby it isrender'd more un-fit to yield thofe Principles, or Partsin Preparation, which the Phylicianrequires to be drawn out. Whatconcerns the Controveriy of its be-ing an Acid ax Alkali,is too triflingfor our Notice here ; we fhali onlytherefore inquire, by what manifeftProperties this Metal comestoaifbrdfo much of moment in PhyiicalPreparations.

And to this purpofe, thus far incommon may be concluded, as fromall other Metalline Particles; Thatfuch as can be mixed with the Blood,and made part of the circulatingFluid, muft of courfe, by the ne-ceffary Laws of Motion, from theirfoperior Gravities, be ofgreat forceto break their way, where Particlesof lefs Gravities cannot get rhro.For Mechanics teach nothing moreplainly, than that the Momenta ofall I'ercujfions are as the Reftanglesunder the Gravities and Celerities ofthe moving Bodies. By how muchmore Gravity then, a metalline Par-ticle has more than any other Par-ticle in the Blood, if their Celeri-ties are equal, by fo much the greaterwill the ftroke of the metalline Par-ticle be, againft every thing that(lands in its way, than of any othernot fo heavy : and therefore willany Obftruclion in the Glands andCapillaries be fooner remov'd byfuch Particles, than by thofe whichare lighter. This is a way ofReafoning that is plain to themeaneft Capacity ; and altho itmay be call'd Mathematical, aName terrible to fome in Phytic,S 4 yet

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