4 THE BOOK OF THE LANTERX. 



creasing the light from any lantern by using a parabolic 

 reflector behind the lamp or candle flame. The passage 

 (translated) runs as follows : 



" To construct an ingenious lantern which may show 

 things written at a great distance so that they can be 

 read 



" Let a lantern be made of the same cylindrical figure 

 C 



PIG. 2. 



as you see here represented, in whose base let a concave 

 mirror be placed, having as parabolic a shape as is possible. 

 Within the focus of this mirror let F, the flame of a 

 candle, be fixed, and you will have "what is required, for 

 it will shine with such unwonted splendour as to show by 

 night, without any trouble, even the smallest letters when 

 examined by the aid of a telescope. But persons looking 

 at the flame from a distance will think that it is a great 

 fire. If the inner sides of the cylinder are fashioned of 

 polished tin in the form of an ellipse, they will increase 

 the light. But the figure here given will sufficiently show 



