orange may be produced. Directions are given for using the top on the lantern, and casting the colors on the screen, so that a great many persons may see it at once.

Another method of producing these recompositions is illustrated in Fig. 11. We have here a square piece of board for a base, an upright block at the corner, two pieces of glass to which the dotted lines

run, and in which reflections are to be seen at the spots where the lines meet, and three pieces of paper at A, B, and C, painted respectively red, green, and violet. The image of A is supposed to go through