In painting these slides, all the glass in the frame around the figures is to be blackened with the opaque black, so that all light is excluded except that which comes through the figures. When this slide is painted, varnish it and paste a narrow strip of paper on the top and bottom of the glass for the movable glass to slide on without scratching the picture.
The black patches on the movable glass are painted and varnished on the inside of the glass. To get these in the right place, place the glass in position over the picture, and when pushed in as far as it will go, mark with your black on the outside of the glass the outline of the arm that is to be covered in that position; then pull out the glass as far as it will go and mark in the same way the outline of the other arm; turn the glass over and fill in the outlines with opaque black, and on putting the glass in its place in the frame you will have a figure with its arms raised or lowered. Now put the glass in its place, and fix it there by pressing into the wood of the frame two small pins at the top and two at the bottom. In putting in these pins allow room for the glass to slide easily.
The construction of lever slides is something like that of the slipping slides, except that the movable glass is circular, and the picture on the glass in the frame is painted circular and has a background. The movable glass has painted on it only the limb that is to be moved. You can get these circular glasses cut at a glazier’s; have them three inches in diameter. Fig. 7 will explain how the two glasses are to be painted. By placing the movable glass over the fixed glass, and moving it partly round and back again, the two boys will appear to move up and down. Of course the point that the board hinges on must be in the centre of the picture. Before painting the picture, cut out a piece of thin board a quarter of an inch thick, three inches wide, and six inches long. Cut this in the shape of Fig. 8 (the dark part represents the wood). Glue this wood on to the glass inside the frame, and cut away the front edge of the frame down to the glass.
Now you can paint your picture, and while that is drying take one of your circular glasses and fit a rim--made of thin brass plate, a sixteenth of an inch thick--to it. This rim is to fit the glass tightly, and is to be a quarter of an inch wide; the ends are to lap a little, and are to be soldered together. Now cut from the same brass plate a strip two and a half inches long and a quarter of an inch wide, and solder this on to the rim, as in Fig. 9. Fix the circular glass in this rim, and on the inside paint the board and children on it, put it in its place in the circular hollow in the frame, and fasten it in its place with small pins pressed into the wood and bent over the brass rim (Fig. 10). By raising or lowering the lever the board will rock up or down.