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X.— THE DOUBLE QUADKIFOKM LIGHTHOUSE LAMP. 

 By PEOFESSOE W. F. BAEEETT. 



[Read, December 16, 1886.] 



It may be of interest to lay before the Members of this Section of 

 the Royal Dublin Society some observations which I have recently 

 had the opportunity of making upon the fog-penetrating power of 

 the new system of lighthouse illumination devised by Mr. J. B>. 

 Wigham, of Dublin. 



As Professor Tyndall has remarked in a recent letter to The 

 Times, when Mr. Wigham began his experiments the best light- 

 house lamp in general use was the four-wick oil-lamp, and the 

 augmented illuminating power in lighthouses which exists at the 

 present day is very largely due to the competition which Mr. 

 Wigham's superior light has called forth. As is well known, 

 Mr. Wigham is the inventor of gas illumination for lighthouses, 

 and the adaptability of gas for this purpose has enabled him to 

 build up a series of three, four, and now eight lights, with their 

 appropriate lenses, within one lighthouse. The high temperature 

 within the lantern produced by so many lights has not, I under- 

 stand, in any of the trials made in Ireland, been found to be dan- 

 gerous to the lenses, and whilst a high temperature is favourable 

 to the illuminating power of coal-gas, it would, I imagine, be fatal 

 to the employment of mineral oils instead of gas. The latest and 

 most powerful arrangement which Mr. Wigham has made is the 

 so-called Double Quadriform light (figs. 1 and 2). This consists 

 of four superposed 88-jet gas-burners (B.B., &c.) placed alongside 

 of four similar superposed sets, the eight lights being in one plane : 

 parallel to this plane, and at the proper focal distance, are placed 

 eight annular lenses on one side, and eight similar lenses on the other 

 side of the gas-burners. Over each of the burners a chimney is fixed ; 

 these lead into a central flue, C, so arranged that no appreciable 

 interference with the light is produced. The recent experiments 

 made at South Foreland show that similar superposed lights blend 

 into one within 1500 feet from the lighthouse ; and when this occurs 



