1889.] on Beacon Lights and Fog Signals. 437 



gas and oil, and they are of the same general arrangement for com- 

 bustion, except that the oil burner is j^i'ovided with cotton wicks. 

 Both produce flames of nearly the same form, dimensions, intensity, 

 and colour. 



The first application of coal gas to lighthouse illumination was 

 made at the Troon lighthouse, Ayrshire, in 1827 ; and in 1847 it 

 was adopted at the Hartlepool lighthouse, Durham ; when for the 

 first time it was employed in combination with dioptric apparatus of 

 the first order of Fresnel. The slow progress made with coal gas in 

 lighthouses, except for harbour lights, where the gas could be obtained 

 in their vicinity, as at Hartlepool, was chiefly due to the great cost 

 incurred in the manufacture of the small quantity required, and at 

 the usual isolated positions occupied by coast ligLthouses, involving 

 extra cost both for labour and for the extra transport of the coal. In 

 1865 the attention of lighthouse authorities was directed to gas as an 

 illuminant for lighthouses by Mr. John R. Wigham, of Dublin, whoso 

 system was tried in that year at the Howth Bailey lighthouse, Dublin 

 Bay. The gas burner of Mr. Wigham, one of which we have here, 

 consists of seven concentric rings, of single flat-flame burners, amount- 

 ing in the aggregate to 108. The burner is used without a glass 

 chimney, and thus there is no appreciable condensation of the group 

 of flames for their employment at the focus of optical apparatus, and 

 the relative aggregate intensity of the ^seven rings of flat flames per 

 unit of focal area, as compared with the four concentric flames of the 

 old four- wick oil burner of Fresnel, are only 2^ per cent, higher 

 than the latter. The burner has five powers for varying states of 

 the atmosphere. For the minimum intensity 28 jets are employed, 

 and with the whole 108 jets there is a maximum aggregate intensity 

 of the flames, with cannel gas, of about 2500 candle units. Several 

 lighthouses on the coast of Ireland have been illuminated with gas 

 on the system of Mr. Wigham, and two at Haisboro, on the coast of 

 Norfolk. In 1878 Mr. Wigham installed at the Galley Head light- 

 house, County Cork, his system of superposed gas flames and group 

 flashing light, which consisted of four of his large gas burners 

 vertically superposed. In conjunction with these were four tiers of 

 first order annular lenses, eight in each tier. By successive lowering 

 and raising of the gas flames at the focus of each tier of lenses, he 

 produced his group flashing distinction. This light shows, at periods 

 of one minute, instead of the usual single flash from each lens, or 

 vertical group of lenses, a group of short flashes, varying in number, 

 between six and seven. The unavoidable uncertainty with this 

 system in the number of flashes contained in each group is unfor- 

 tunate for the mariner, who, with the continued increase in the 

 number of coast lights, requires the utmost precision in the distinctive 

 character adopted for each. 



In 1857 an experimental trial of the first magneto-electric machine 

 of Holmes, for the practical application of the electric light, was made 



