432 IMAGES FORMED BY REFLECTION. 



which are differently shaped on both sides, as, for ex- 

 ample, the hand, many letters, &c. ; thus the image of the 

 right hand is like the left hand, the image of the letter 

 p is like the letter q. This is called lateral inversion, 

 and in all these cases the reflection does nothing more 

 than shift the, .point of divergence of the rays, from 

 right to left, and from left to right. If the image is 

 again reflected from a second mirror, lateral inversion 

 takes place a second time, and the second image is 

 therefore in every respect like the original. If two 

 plane mirrors, S S l and S /S' 2 , in fig. 245, are placed 

 vertical and at right angles, their edges touching one 

 another, an object placod within the angle will in the 

 first instance produce one image in each mirror, B^ and 

 J3. 2 ; but each mirror with its image is again reflected 

 by the other mirror ; these reflected images must 

 obviously mutually coincide, and hence a third image, 

 J9 3 , is produced, which agrees in every respect with the 

 original object. 



Two rectangular pieces of good silvered plate-glass, not less than 

 15 cm long and 10 cm wide, or still larger if possible, are placed upon 

 pieces of cardboard of the same size, so as to protect the silvering, 

 and glass and cardboard are fixed together all round the edges with 

 strips of black paper, or fine ribbon, glued to the sides, so that onlv 

 a very small edging is left round the reflecting surface. The back 

 of the cardboard may be covered with paper to give it a better 

 appearance. The two mirrors are joined together along the smaller 

 side by hinges of black ribbon, as long as the mirrors are wide, 

 and glued across the back of the mirrors, while these are placed 

 with exactness over one another, their reflecting sides being in 

 close contact. The mirrors will open and close afterwards like a 

 book, and may be inclined to one another at any angle and placed 

 in a vertical position upon any horizontal surface. 



Place them in this manner nearly at right angles, and look at the 

 edge where they join.. The image J? 3 will at first appear inexact : 

 either a piece in the middle will be wanting, or it will appear double. 



