be formed at g h. The image, therefore, and not the object, is viewed by the eye D Е, through the lens e f, which is so placed that the image g h may be in its focus, and the eye about the same distance on the other side; the rays of each pencil will be parallel after going out of the eye-glass as at e and f, till they come to the eye at k, where they will begin to converge by the refractive humour of the eye, and having crossed each other and passed through the crystalline and vitreous humours, they will form the inverted image A B on the retina. There are generally two eyeglasses, by which means the object is less magnified, but more of it is seen.

The solar microscope depends on the sunshine, and is used in a darkened room. It is composed of a tube, a looking glass, a convex lens, and a single microscope. The sun's rays are re. flected by the looking-glass through the tube upon the object, the image of which is thrown upon a wbite screen, sheet, &c. placed at a distance to receive it. The magnifying power of the instrument is in proportion as the distance of the image from the object glass is greater than the object itself is from it. Thus if the distance of the object from the object glass be of an inch, and the distance of the picture be 10 feet or 120 inches, then the object is magnified in length 480 times.

The mugic lantern, is an instrument used to magnify paintings on glass, and throwing their images upon a white screen in a darkened chamber. Thus Fig. 10, represents the machine with the effect it produces. The lantern contains a reflector which is so situated as to have the light of a candle in its focus. On the fore part of the lan

tern there is a thick double convex lens, or a planoconvex (usually called a bull's eye) of short focus. The fantern is closed on every side, so that no light can come out of it, but what passes through the fens. In the direction of this lens there is a tube & fixed to the lantern, which has a lateral aperture from side to side; through this the glass slider a d' with the painted small images, is moved in an inverted position. The forepart of the tube 20 * contains another sliding tube, which carries à double convex lens. The effect of those parts is as follows: the thick lens throws a great deal of light from the candle upon the image.'' And to increase that light still more a reflector is often, but hot always, placed on such lanterns ; for as the fame is in the focus of the reflector, the light proceeds in parallel lines from the reflector to the lens. The image being thus well illuminated, senás forth rays from every point, which, hy passing through the lens, are converged to a focus upon the wall and form the large images, as is shewn in fig. 10.

The phantasmagoria" is like the magic lantern, only instead of painting the figures on transparent glass, all the glass is opaque, except the Figure only, which being painted in transparent colours the light shines through it, and no light can fall on the screen, but what passes through the figure. The screen is very thin silk between the spectators and the lantern, and by moving the lantern backwards or forwards, the figures seem to recede or approach. 1. ; ** A multiplying glass is made by grinding down "the side of a conves glass into several flat surfaces,