THE ELECTRIC LIGHT AT SEA. 185 



Alan Stevenson states that the earliest notice he has been able to find of the 

 application of paraboloidal mirrors to lighthouses is in a work on " Practical Seamanship " 

 (Liverpool, 1791), by Mr. William Hutchinson, who notices the erection of the four 

 lights at Bidstone and Hoylake for the entrance of the Mersey, in 1763, and describes 

 large paraboloidal moulds of wood lined with mirror glass and smaller ones of polished tin- 

 plate, as in use in those lighthouses. In France M. Teulere, a Member of the Royal Corps of 

 Engineers of Bridges and Roads, is regarded as the inventor of the catoptric system of 

 lights. In a memoir dated 26th June, 1783, he is said to have proposed for the Cordouan 

 Lighthouse a combination of paraboloidal reflectors with Argand lamps, arranged on a 

 revolving frame, a plan which was actually carried into execution, under the direction of 

 the Chevalier Borda."* The plan was so successful that it was soon adopted in England 

 by the Trinity House of London; and in Scotland the first work of the Northern Lights 

 Board, in 1787, was to light a lantern on the Old Castle of Kinnaird Head, in Aberdeen- 

 shire, by means of parabolic reflectors and lamps. These reflectors were formed of facets 

 of mirror-glass placed in hollow paraboloidal moulds of plaster. The more complicated 

 arrangement of lenses placed round a centre in concentric circles is due to the great 

 Fresnel, a practical man of science, whose abilities are acknowledged as fully in England 

 as in France. 



The oil used in the lighthouses of the United Kingdom has generally been sperm. 

 Colza, the expressed oil of the wild cabbage (Brassica oleracea), was very generally used 

 in France, and occasionally in Great Britain. Gas is used in a few places, where its 

 application is easy. There can hardly be any doubt now, however, that the coming light 

 will be the electric, since its steady production is becoming a matter of scientific certainty. 

 As early as 1857 Professor Holmes submitted to the Trinity House a method of employing 

 this light, which was submitted to Faraday, and approved. The Board then allowed a 

 trial at the South Foreland Lighthouse. The light was first displayed on the 5th of 

 December, 1858. In June, 1862, it was permanently fixed at Dungeness. In Faraday's 

 Report to the Trinity House, published in 1862, he says: "Arrangements were made on 

 shore by which observations could be made at sea, about five miles off, on the relative 

 light of the electric lamp and the metallic reflectors with their Argand oil-lamps, for 

 either could be shown alone, or both together. At the given distance the eye could not 

 separate the two lights, but by the telescope they were distinguishable. The combined 

 effect was a glorious light up to five miles; then, if the electric light was extinguished, 

 there was a great falling off in the effect, though, after a few moments' rest to the eye, 

 it was seen that the oil-lamps and reflectors were in their good and proper state. On 

 the other hand, when the electric light was restored, the glory rose to its first higli 



condition During the day-time I compared the intensity of the light with that 



of the sun, and both looked at through dark glasses. Its light was as bright as that of 

 the sun, but the sun was not at its brightest/' 



The number of lights on a well-frequented coast being considerable, it is of the 

 utmost importance to arrange them so as to enable the mariner easily to distinguish 



* M. Quatrefages de Breau, the distinguished French naturalist and philosopher, says tkat the revolving 

 apparatus was partially due to M. Leinoine, a citizen, and at one time Mayor, of Calais. 



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