CONTENTS. T ii 



PAG* 



Varies with distance of object. 13. Peculiarities of vision in short 

 sight explained, 14. In long sight. 15. The mounting of spec- 

 tacles. 16. Periscopic spectacles. 17. Both eyes have not 

 always the same power of vision. 18. Ophthalmometer. 19. 

 Application in selecting glasses. 20. Curious defects of vision . 193 



THE KALEIDOSCOPE. 



1. Origin of the name. 2. Structure of the instrument. 3. Its optical 

 effect. 4. Varieties of its form. 5. Its occasional use in the 

 arts. 6. Another optical toy depending on two reflections . 205 



