R. of this copper one part, and of latton [_Orichalcum_] two parts, melt it with a very quick Fire, and first indeed the latton, to which afterward add the friable copper; pour out the mixture melted and thou shalt have a very hard metal unfileable, yet not so brittle, but like steel, of which diverse things may be formed serving in stead of iron and steel instruments; take of this hard metal three parts of the best tin without lead one part, melt and effuse it, and the matter of looking-glasses will be made. This mixture is a hard white metal making the best looking glasses, but if this labor seem tedious, take of copper three parts, of tin one part, of white Arsenick half a part for the matter of looking-glasses, which are fine but brittle, as well in the melting as polishing, therefore carefully to be handled. I must here set down a thing worthy to be observed, and known to few; _viz._: a false opinion of many, especially of those who attribute knowledge to themselves of the proprieties of metals. In the second part (of subtile spirits) mention is made of the pores of metals, for experience witnesseth, that those subtile spirits as of harts-horn, tartar, soot, and sometimes those sulphureous ones of salts and metals do evaporate through pewter vessels, which at the first hearing every man cannot conceive, for whose sake this discourse is made. Make two balls of Copper, and two of pure Tin not mixt with lead, of one and the same form and quantity, the weight of which balls observe exactly, which done, again melt the aforesaid balls or bullets into one, and first the copper, to which melted add the Tin, lest much Tin evaporate in the melting; & presently pour out the mixture melted into the mold of the first balls, and there will not come forth four nor scarce three balls, the weight of the four balls being reserved; if then metals are not porous, whence I pray doth that great alteration of quantity proceed? therefore know that metals are porous more or less; gold hath the fewest pores, silver hath more, Mercury more than that, Lead more than Mercury, Copper more than Lead, and Iron than copper, but tin hath most of all.