J84 report— 1884. 



Improvements in Coast Signals; with Supplementary Remarks on 

 the Neiv Eddystone Lighthouse. By Sir James N. Douglass, 

 MJnst.CE. 



[A communication ordered by the General Committee to be printed hi extcnm 



among the Reports. J 



[Plates IV. and V.] 



The successful development of the maritime commerce of any country 

 must always be very largely dependent on the perfection of its system cf 

 coast signals for the guidance of the mariner. Therefore, when we reflect 

 on the important progress made by the Dominion of Canada, occupying, 

 as she now does, the fourth position of the maritime countries of the 

 world, the present occasion of the visit of the British Association to Mon- 

 treal would appear to be a fitting time for the consideration of recent and 

 future advancement in the development of coast signals. 



The installation of the fog-whistle by Daboll at Beaver Tail Point, 

 Rhode Island, in 1851, and the installation of the electric light by Holmes 

 nt the South Foi-eland, in 1858, were two of the most important steps in 

 the progress of coast signals. Since these dates light and sound coast 

 signals have so developed that it is now found to be possible, at any coast 

 signal station, to render trustworthy service to the mariner by one or 

 other of these agents in all the varying conditions of the atmosphere— — 

 1st, by providing a reliable and efficient signal ; 2nd, by giving it such a 

 clearly distinctive character as to enable the mariner to determine accu- 

 rately his geographical position. 



The light of the four concentric wick oil lamps for the dioptric lights 

 of the first order of Fresnel had an intensity of 230 English candle 

 units. The electric arc light, first practically produced by Holmes, and 

 experimentally installed at the South Foreland in 1858, had an intensity 

 of about 700 candle units. 



Compact flame luminaries are now being produced from mineral and 

 other oils, and coal gas, by improved burners, as shown on the drawing 

 No. 1, having an intensity of 1,500 to 2,000 candle units. "With the 

 ' Wigham ' gas-burners, consuming rich cannel gas, an intensity of 

 nearly 3,000 candles has been reached ; but the flames from these burners 

 have been found to be so wanting in focal compactness, and consequently 

 so much loss is incurred with their application to optical apparatus of the 

 dimensions convenient for' service in coast lighthouses of the first class, 

 that the intensity of the resultant beam is not found to exceed that of the 

 more compact flame of lower intensity and consumption of oil or gas. 

 With the electric light an intensity of 50,000 candle units is now found 

 to be practically and reliably available for the focus of an optical appa- 

 ratus for coast lighting, so that, with regard to intensity and consequent 

 penetrative power, this luminary is found to outstrip all competitors. 



With regard to economy, and doubtless for a very wide and general 

 application, mineral oil has the advantage of all its rivals up to the maxi- 

 mum intensity at which flame luminaries are practicable. It has also the 

 further advantage over electricity or gas in its ready application at any 

 coast signal station, however isolated, and in many cases where the other 

 luminaries referred to would be impracticable. A very elaborate and ex- 



