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SCIENTIFIC APPARATUS. 



Euclidean space, in which form and magnitude do not remain the 

 same when a figure is moved from one part of space to another, 

 but are themselves functions of the position. Cylindrical and 

 conical mirrors have been used for showing the effect, known as 

 the anamorphosis, whereby drawings suitably distorted are restored 

 to their proper proportions. Conical mirrors, or reflecting cones, 

 which must be of glass, serve also for producing radial polari- 

 sation. Parabolic, and other curved mirrors, are used in light- 



houses for illumination, and in reflecting telescopes. The rays 

 from a luminous point, placed in the focus, are reflected by a 

 parabolic mirror in a parallel beam of light ; and conversely 

 parallel rays, as those from the sun, are collected by parabolic 

 reflectors at the focus. 



The amount of light reflected from the surfaces of various media, 

 and at various angles, has been the subject of much careful 

 experiment. "When the light is polarised the question becomes a 

 very profound one. 



