REFLECTION OF LIGHT. 307 



duced, and if the light were not gradually weakened hy 

 loss at each successive reflection, the number would be in- 

 finite. 



If the mirrors are placed so as to form an angle -with each other, the num- 

 ber of mutual reflections will be diminished, proportionably to the extent of 

 the angle formed by the mirrors. 



_, .^ ,, The construction of the optical instrument called the Kalei- 



Descnbe the , . _ 



Kaleidoscope. doscope IS based simply upon the multiplication of an image 



by two or more mirrors incUned toward each other. It con- 

 sists of a tube containing two or more narrow strips of looking-glass, which 

 run through it lengthwise, and are generally inclined at an angle of about 

 60°. If at one end of the tube a number of small pieces of colored glass 

 and other similar objects are placed, they will be reflected from the mirrors 

 in such a way as to form regular and most elegant combinations of figures. 

 An endless variety of symmetrical combinations may be thus formed, sinco 

 every time the instrument is moved or shaken the objects arrange themselves 

 differently, and ^ new figure is produced. 



_, , ^, Upon the surface of smooth water the sun, when it is nearly 



Why does the ^ ' ^ 



Bun appear at vertical, 33 at noon, appears to shine upon only one spot, 



noon to shine ^U the rest of the water appearing dark. The reason of this 

 point upon the is, that the rays fall at various degrees of obliquity on the 

 water ? Water, and are reflected at similar angles ; but as only those 



which meet the eye of the spectator are visible, the whole sur- 

 face will appear dark, except at the point where the reflection occurs. 



jijQ 241 Thus, in Fig. 241, of the rays 



S A, S B, and S C, only the ray 

 S C meets the eye of the specta- 

 tor, D. The point C, therefore, 

 will appear luminous to the spec- 

 tator D, but no other part of tho 

 surface. 



Another curious optical pheno- 

 D menon is seen when the rays of 

 the sun, or moon fall at an angle 

 upon the surface of water gently 

 agitated by the wind. A long, 

 tremulous path of light seems to 

 be formed toward the eye of the 

 spectator, while all the rest of the 

 surflice appears dark. The reason 

 of this appearance is, that every little wave, in an extent perhaps of miles, has 

 Bome part of its rounded surface with the direction or obliquity which, accord- 

 ing to the required relation of the angles of incidence and reflection, fits it to 

 reflect the light to the eye, and hence every wave in that extent sends its mo- 

 mentary gleam, which is succeeded by others. 



