THE MAGIC TELESCOPE. 233 



of absorbing all of the light which falls upon them except 

 that portion which forms the color which they present to 

 the eye. And this, as was stated at the close of the last 

 chapter, is the philosophy of color. 



In respect to the regular and systematic reflection which 

 is produced from smooth and polished surfaces, if the sur- 

 faces are plane, the rays are reflected, as has already been 

 explained, in such a manner that their relative condition 

 in respect to each other is not changed. The whole beam 

 is turned out of its course, it is true, but without any 

 change in its internal constitution, and the image which it 

 is capable of producing in the eye is not changed in its 

 form or in its magnitude, but only in its apparent place. 

 When the reflecting surface is not plane, but is of some 

 other regular mathematical form, as, for example, when it 

 is concave, convex, cylindrical, or conical, the rays are re- 

 flected with regularity, so as to form images on the retina 

 of the eye; but these images are enlarged, or diminished, 

 or changed in various ways, according to the effect of the 

 surface in modifying the directions of the rays in respect 

 to each other. The eye, it must always be remembered, 

 can take cognizance of the rays only when they enter it, 

 and is wholly unconscious of any change of direction which 

 they may have been subjected to on their passage. 



There is a very curious piece of apparatus, called the 

 magic telescope, which serves admirably to illustrate this 

 principle. 



There is a stand with a concealed channel passing 

 through it, in which small square pieces of looking-glass 

 are fixed at angles of 45, one at each end. Above these 

 ends are two upright tubes which have the appearance 

 only of simple supports, though they are really hollow. 

 Upon each of these supports are two short tubes, like tele- 

 scope tubes, with an open space between them. In each 



