138 



SCIENCE. 



[Vol. I., No. 5. 



taken account of, in the above figures, the light 

 of the foyer itself, independently' of the opti- 

 cal apparatus ; which, bj^ conceA,trating the 

 raj's, augments the intensity yery considerably. 

 The number of electric lights comprised in 

 the project is forty-six, counting as two the 

 double lights of la H6ve, of la Canche, and 



other ; and, where there is a gap, it will be 

 filled with an oil-light. This map also gives 

 the distinctive characteristics of the different 

 lights, and this is a most important point to be 

 considered. 



In a good system of coast-lights, the neigh- 

 boring lights should have very distinctive 



of Hourtin. Of this number there are thirtj'- 

 eight of the first order, two of the second 

 order, five of the third order, and a new one 

 to be placed at the south of Paimpol. Four 

 of these lights are already, or are about to be, 

 lighted electrically. 



As to the distribution of the lights, it is 

 easy to follow it upon the map, Fig. 1 : almost 

 everj'where the circles of ranges cut each 



characteristics, in order to avoid all possible 

 confusion. In the existing S3'stem, these con- 

 ditions obtain ; and the first idea which natu- 

 rally' presented itself was to retain the old 

 characteristics, simplj- substituting the electric 

 for the oil light, so that there would be no 

 change from that to which sailors were accus- 

 tomed : but the existing characteristics are, in 

 some waj's, inconvenient, and it has been de- 



