WiGHAM — Improvements in Lighthouse Lights. 149 



conclusion of the lecture the audience had an opportunity of 

 making the experiment for themselves.] 



The cannel gas now used in lighthouses has an illuminating 

 power of 27 to 29 candles, or, roughly speaking, nearly double that 

 of ordinary Newcastle coal (16 candles), consequently if I had 

 used cannel gas in the left-hand burner, the new light, instead of 

 being four times its power would be only twice its power. This 

 statement seems obvious, and I have practically jDroved its correct- 

 ness many times in the Photometer room of Edmundson's works, 

 where I have the means of making and storing both cannel gas 

 and common gas — that is, I made the same experiment as that 

 at which you have been looking, but with cannel gas at one end 

 of the photometer and the new burner at the other. I had recently 

 the pleasure of doing this in the presence of a number of scientific 

 gentlemen and others, amongst whom were some of the Commis- 

 sioners of Irish Lights, Sir Eobert Ball, F.E.S., their scientific 

 adviser, and Mr. William Douglas, Engineer to the Commissioners, 

 and proving to them that the new burner was of twice the illumi- 

 nating power of the most powerful lighthouse burner consuming 

 cannel gas. 



The highest illuminating power yet reached by any gas burner 

 is that recorded in Parliamentary Paper C. 1151, page 42, for the 

 108 jet Wigham burner (Tory Island type), viz. 2923 candles. 



The next is that recorded at page 42 of the Trinity House 

 Eeport for the Douglas 10-ring burner (Bull Eoek type), 2619 

 candles. 



The new burner, at which we have been looking, by which the 

 intensity of the fiame is doubled, while its volume is in no way 

 diminished, represents therefore an illuminating power of close to 

 6000 candles, more than twice the highest power recorded of any 

 burner, and this, in quadriform, as at Galley Head, would bring 

 up the illuminating power to about 24,000 candles. 



Another improvement in lighthouse illumination which I have 

 suggested is that lenses should be so placed as to form a quadri- 

 lateral or a trilateral figure. Heretofore lenticular apparatus for 

 lighthouses have been hexagonal, octagonal, or even sixteen-sided, 

 but the quadrilateral form admits of the use of lenses of much 

 larger illuminating surface and of much longer focal distance than 

 is possible with six or eight-sided lenticular apparatus, and thus 



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