Cut out of strong cardboard a piece of about 2 to 2-1/4 inches square. In the middle cut out a circle a little smaller than the lens with which you cover it, so that this lens holds on the edge of the hole. Cut out also two triangles of cardboard, having one side equal to the square, and a length in proportion to the focus of the lens; say for a simple lens of 3 inch focus, and one inch diameter, a length of one and a half inches. [Illustration: Fig. 2.] Paste the two triangles on the square at A and B, their base C must hold a rectangular mirror of the same dimensions as the side C of the square and the side of the triangles. On side D fix a roughened glass pane, or instead, a thin transparent sheet of paper; tissue paper for example. [Illustration: Fig. 3.] Cut a black piece of cardboard as indicated in Fig. 3 C; the dotted lines indicate the sides to be turned down. This shade is fixed on to the camera. [Illustration: Fig. 4.] Pass through the holes, S S, an iron rod or a long needle, which must pass likewise through the upper angle of the triangles, forming the sides, (Fig. 1). When your lens has been fixed on the round hole of the square your camera is complete. The shade produces complete obscurity so that the operator can see in the middle of the camera the object or person he wishes to photograph. In order to fix it on the photographic apparatus, one may fasten a wire, in the form of an elongated U, just below the mirror at E. The Phantom Needle. You know that when you sit at a window with a looking-glass in your hand, you can catch a beam of sunlight on the glass and throw it into the eyes of a person on the other side of the street. [Illustration] What have you done in this case? You answer at once that you have bent the sunlight out of its course and turned it in another direction. If the glass were not there it would fall in a straight line on the window seat. This bending out of the straight line is called reflection. Now for an experiment; cut a small round piece of cork, not quite half an inch thick. Run a needle into its center and place it in a tumbler two-thirds full of water, needle downwards. Looking down on the cork you cannot see the needle. Now alter your position, and stoop down so that your eye is on level with the table on which the glass stands. Then you will perceive the needle to be on the top of the cork. This apparent topsy-turveydom is called total reflection. The needle is reflected on the top of the water, and as the ray from your eye meets the top of the water, you see the needle, as it were, on the top of the cork. Amphitrite. At fairs, and in halls of mysteries a variety of optical illusions are presented. Under the name of Amphitrite, the spectacle is sometimes of a woman who seems to rise from the deep, moves about in the empty space, apparently without being sustained by anything or anybody.