The art of glass shewing how to make all sorts of glass, crystal and enamel : likewise the making of pearls, precious stones, china and looking-glasses : to which is added, the method of painting on glass and enameling : also how to extract the colours from minerals, metals, herbs and flowers ... : illustrated with proper sculptures / written originally in French, by Mr. H. Blancourt, and now first translated into English ; with an appendix, containing exact instructions for making glass-eyes of all colours.

CHAP. CCLVI. To Polish the Steel Mirrours.

WHATSOEVER Exactness you use in Mould∣ing these, they do never receive their true Shape and Perfection, until they are Polished and Burnished; in doing which, least you should spoil, or endamage them, you must Work away the Out∣side at the Wheel, with the Sand-stone, which the Pewterers and Brasiers make use of, and then apply the Handle, and Polish them sufficiently by rubbing with Water.

This done, take it off this Wheel, and put it on the Second, where rub it with Emery prepared, that

it may be finely polished, so as the Scars may be scarce perceptible. Do this in an Oblique Line.

Then take it off this, and set it on such another; rub it with Blood-stone prepared, and afterwards use Calx of Tin, working it for a long time, until it have its due Burnish and Perfection, still doing it in the same Obliquity.

You must keep these Mirrours from the Moistness of the Air, and Steams; or if they should happen to be endamaged by any such, you may restore them by rubbing on them a piece of Deer, or Goats Skin, humouring the Oblique Line; you must not use any Woollen, or Linen Stuff, for they spoil these Mir∣rours.

These Mirrours may be also polished with Lead Artificially melted, with Emery and Water, for the First Process; and very fine Emery and Lead for the Second; and in the Last, with Blood-stone and Tin Dross; these make a finer Burnish than the for∣mer; for the Mirrour is highly polished by the Tin-Dross.

This is all we resolve to give account of on these sort of Mirrours, for attracting and uniting the Sun Beams. There are many other, as Cylinders, Py∣ramids, whereof we forbear to discourse, since the Authors which have writ of them, have done it with much more sufficiency than we pretend to.

They ascribe the first Invention of Burning Mir∣rours to Prometheus, when he stole the Fire from Heaven to carry to the Earth. Archimedes made ve∣ry happy use of them in defence of his Country, when he burnt the Fleet of Marcellus before Syracuse, by placing his Burning Glass on the highest Turret in the City, whence proceeded such a mighty Confla∣gration, as destroy'd that vast Flota in spight of Neptune and the Waters. Proclus too, a Brave and Famous Mathematician, burnt the Fleet of Vitelian,

that came to Besiege Constantinople; which he pre∣served by this Industry.

Many other Fine and Admirable Relations might be given of the Effects of these Mirrours, but they are too tedious: We shall therefore here put an end to this Chapter, and consequently the whole Book, desiring the Reader to receive all in good part, and excuse the lesser Faults of Impression and Phrase, since we can assure him the Doses are justly prescri∣bed, and the Preparations exact which we have as∣signed.