116 VERY HEIGHT LIGHTS. 



CHAPTER 



VERY BRIGHT LIGHTS. 



FOR such performances as those which Lawrence and 

 John witnessed at the Polytechnic, and also for many oth- 

 er purposes, a very bright light is required. There are 

 modes of producing artificial light of such intense bril- 

 liancy that you can not look upon it directly with the 

 naked eye for a moment. 



But, though we can not look upon the light itself with- 

 out dazzling the eye, the illumination which it produces 

 when shining upon other objects, though exceedingly 

 bright, is very beautiful to see. Then, moreover, when 

 objects are to be seen by reflection in a glass, there is great 

 advantage in being able to illuminate them by a light so 

 strong that it can not be viewed directly without dazzling 

 the eyes. 



Besides this, there are a great many cases in which light 

 is diminished by diffusion instead of by reflection, and as 

 the diffusion weakens it, as has already been explained, in 

 the ratio, for similar purposes, of the squares of correspond- 

 ing lines, the light must be very bright indeed at the 

 source, in order that it may be bright enough after diffu- 

 sion. 



The engraving on the opposite page, for example, repre- 

 sents what is called a magic lantern. It consists of a kind 

 of lantern, with an apparatus within it capable of produc- 

 ing an intense light, and also of concentrating this light at 

 a point, from which it afterward diverges in such a manner 

 as to produce an enlarged shadow, or image, of any minute 



