APPLICATIONS OF THE ELECTRIC LIGHT. 283 



Application to Submarine Working. Since diving, 

 bells and various other apparatus for supporting respiration 

 under water have made it possible to work at the bottom of 

 the sea, several kinds of hydraulic work, and numerous re- 

 coveries of sunken vessels have been executed with ease. 

 When the depth of the water which is to be entered is not 

 great, daylight readily penetrates the liquid layer and affords 

 sufficient light to the workers'; but at a certain depth the 

 light fails, and the submarine explorations, which must 

 always precede the working, become impossible. No doubt, 

 by fitting a lantern with apparatus for renewing the air, a 

 light may be maintained as men's respiration is maintained ; 

 but this necessitates a supplementary pump and special 

 apparatus to prevent the current of air from extinguishing 

 the light. With the electric light the problem is solved in 

 the simplest manner, and the extent of the space illuminated 

 is much greater. The regulator with a globe, which we have 

 already mentioned, may be used, or a special regulator to 

 give the light directly in the water. However, as the light is 

 in this last case much more difficult to control than when it 

 is vacuo, the former method is to be preferred. 



The experiments made at Dunkirk on fishing by the electric 

 light have allowed the way in which the light behaves under 

 water to be examined, and it has been found that magneto- 

 electric machines, as well as the light they produce, are cer- 

 tainly applicable to submarine working. At a depth of 60 

 metres the light remained quite steady, and it illuminated a 

 very large surface. The machine, moreover, was placed at 

 more than 100 metres from the regulator. The surface of 

 the glass in the lantern remained perfectly transparent, and 

 the consumption of the carbons was less than in the open 

 air. 



Applications to the Projections on a Screen of 

 Optical Experiments, Photographic Transparencies, 

 &c, There are many physical phenomena which require 



