396 POPULAR LECTURES AND ADDRESSES. 



ism is also applied in many cases to produce the 

 eclipses of " Occulting or eclipsing lights." The 

 official description of the revolving light in the 

 " Admiralty List of Lights," is as follows : 



" Rev. Revolving light, gradually increasing to 

 full effect, then decreasing to eclipse. [At short 

 distances and in clear weather a faint continuous 

 light may be observed.] " 



This, in fact, includes the description of the 

 flashing light : 



" Fl. Flashing showing flashes at short inter- 

 vals, or groups of flashes at regular intervals." 



A combination of the fixed and flashing qualities, 

 though comparatively rare, constitutes an important 

 characteristic light, described in the Admiralty list 

 as follows : 



" F. and FL Fixed light with addition of white 

 or coloured flashes, preceded and followed by a 

 short eclipse." 



Thus we have really very little of complexity in 

 the fundamental classification into the three 

 descriptions of Flashing Fixed, and Occulting. 



In the flashing light, the light is visible for only 



