ACCESSORY INSTRUMENTS 



147 



this careful adjustment of the light. The rays, passing 

 through the objects, strike rather downwards upon the mirrors, 

 and are again reflected rather upwards ; and in many instru- 

 ments the effect is better if the front lens is somewhat in- 

 clined, so as to be perpendicular to the course of the rays. 

 The kaleidoscope should always be warmed before use, to 

 prevent dew upon the mirrors, if the night is at all cold. 



I have seen a beautiful lantern kaleidoscope, specially 

 constructed by Mr. Darker, in which the mirrors were adjust- 

 able by a screw to any angle through a considerable range. 

 Such a form must necessarily be expensive ; but an instrument 

 of this kind is far removed from a mere lantern toy, and 

 becomes at once an exquisite piece of experimental appa- 

 ratus for demonstrating the laws and phenomena of multiple 

 reflection, 



FIG. 77 



Aphengescope 



FIG. T8 



80. Opaque Pictures. Another simple instrument for 

 exhibiting cartes de visite and other opaque objects, such as 

 the works of a watch, is often called the Aphengescope the 

 mania for giving Greek names to lantern affairs is inexplicable 

 to the ordinary mind. The usual arrangements are shown in 

 figs. 77 and 78, one being adapted for two lanterns, and the 



L2 



