Applicability of the Electric Light to Lighthouses. 331 



uniform the electric current may be. The same injurious effect- 

 is produced by very slight alterations of the distance between 

 the points, and by changes of the luminous arch from one side 

 of the points to another, an occurrence which, sometimes takes 

 place. A slight displacement of the focus would throw the 

 rays too high, or depress them too low. No displacement, 

 however, greater than five millimetres, has been observed, 

 which would raise or depress the bundle of rays only through 

 two degrees ; and the light sent from the lighthouse to the 

 horizon would still be in excess of that from the very best oil 

 apparatus. A report was made to the French government, 

 regarding these experiments, in 18G3. 



Two magneto-electric machines have been placed in the 

 double lighthouse on the Cap de la Heve ; and other nations 

 are following the example of England and France, in attempting 

 the introduction of the electric light into lighthouses. 



The reports made to both the English and French, govern- 

 ments, on the application of the electric light to lighthouses, 

 in a great degree coincide, and they enable us to form a very 

 fair idea of the advantages and disadvantages which attend its 

 use. Both agree in the assertion that there has not yet been 

 time to form a final judgment regarding the matter. 



Nothing' can exceed the brilliancy of the electric light ; no 

 other light can compete with. it. Faraday estimates its power 

 at eight times that of a first-class ordinary light ; and he found 

 that it was comparable with that of the sun, when both were seen 

 together. When seen with the ordinary oil light, the extinction 

 of the latter produced no perceptible diminution of effect, nor 

 its being re-lighted, any augmentation. The peculiar bluish 

 tint of the electric light is rather an advantage, since it causes 

 it to be more easily distinguished from other lights. But it 

 may be made of any colour, and intermittent, according 

 to any law. Its capability of being instantaneously extin- 

 guished, and re-lighted, at pleasure, would enable it to be 

 used on parts of the coast where, on account of the difficulty 

 hitherto experienced, of producing lights easily distinguishable, 

 it has not been found advisable to erect lighthouses. The 

 same property also fits it well for signalling ; and it would be 

 very easy to make any lighthouse in which it is used, tell its 

 own number, by means of certain periodical extinctions. It is 

 entirely free from the enormous shadow cast by the oil appara- 

 tus, its descending rays being unabsorbed. 



The intensity of the electric light is not, however, so great 

 an advantage as might, at first, be supposed. The oil light 

 now in use can, as wo have said, be seen quite as far, in fine 

 weather ; and in fogs, sufficiently dense to hide the sun, both 

 become invisible. But, when it ceases to be visible, the engine 



