APPLICATIONS OF THE ELECTRIC LIGHT. 267 



,a little prolonged in front, was closed by a Fresnel lens, in 

 order to transform the divergent beam into a parallel one. 

 Finally, behind the regulator and the reflector was a small 

 spherical reflector. The whole was mounted in a chamber 

 movable on a pivot 

 which, by a lever and 

 rotating platform, per- 

 mitted the beam to 

 be sent in any direc- 

 tion. Further, a ma- 

 rine telescope fitted 

 to the apparatus 

 enabled the points 

 of the horizon lighted 

 by the beam to be 

 observed. By placing 

 in front of this beam 

 coloured glasses, the 

 light could be colour- 

 ed green or red, and 

 thus made suitable for 

 marine signalling. 



In Sautter and Le- 

 monnier's projector, 

 represented in Fig. 

 69, the spherical and 

 parabolic reflectors 

 do not exist, and the 

 whole consists of a 



Fresnel lens composed of 3 droptric and 6 catadroptric 

 elements. This lens is enclosed in a wide cylindrical 

 tube, which, being supported on a pivot with the whole 

 electrical arrangement, can be turned in any desired direc- 

 tion. 



In Siemens' projector, represented in Fig. 70, the para- 

 bolic reflector is placed behind the lamp ; and the latter is 



FIG. 70. 



