A mirror is to be made as follows: first make a hoop or fillet of wood about the width of a half-crown piece, and let the thickness be about a quarter of an inch. In the middle of this hoop fasten a bottom of wood or brass, and place several hooks of the size of small peas. Then open the one side of this bottom, set in a piece of crystal glass, and fasten it in the hoop close to the bottom;
then take a quantity of quicksilver, and put so much into the hoop as will cover the bottom; then let into the hoop another piece of crystal glass fitted thereto, and cement the sides that the quicksilver may not run out, and it is done,—the use whereof I shall not insist upon, since he that is versed in optical illusions will better conceive it, than any words of mine can either direct or assist him.
The Magic-Lantern.
This lantern is called magical on account of the formidable apparitions that, by virtue of light, show upon the white wall of a dark room. The body of it is generally made of tin, and of the shape of a lamp. Towards the back is a concave looking-glass of metal, which may either be spherical or parabolical, and which, by a grove made in the bottom of the lantern, may be either advanced nearer or put farther back from the lamp, in which is oil or spirit of wine; and the match ought to be a little thick, that when it is lighted it may cast a good light that may easily reflect from the glass to the fore part of the lantern, where there is an aperture with a prospective in it, composed of two glasses, that make the rays converge and magnify the object.
When you mean to make use of this admirable machine, light the lamp, the light of which will be much augmented by the looking-glass at a reasonable distance. Between the fore part of the lantern and the prospective glass you have a trough, made on purpose, in which you are to run along a flat frame, with transparent colours on glass. Then all these little figures, passing successively before the prospective glass, through which passes the light of the lamp, will be painted and represented with the same colours upon the wall of a dark room, and in a gigantic and monstrous manner.
By this lantern you may show birds, beasts, and all sorts of fish, &c. &c. &c.
The Phantascope.
The Phantascope is a magic-lantern improved; that is, it will magnify or diminish the figures it is to reflect, without impairing their neatness.
This instrument is composed of a tin box, surmounted by a kind of chimney, pierced on one of its faces with a hole of a diameter corresponding with that of the cylinders, sliding into one another like the tubes of an opera-glass: this tube is adjusted by means of a slide established above the aperture made in the phantascope. The part of the adjoining cylinder is so adjusted to receive alternately wooden tablets, in which are opened cavities to contain the figures painted upon glass. The flat side of the half ball is placed in that tube, nearly close enough to touch the painted figures: this half ball is called the object glass.