RECENT EXPERIMENTS ON FOG SIGNALS. 195 



of the Paris Alliance Company, of Wilde, and of Gramme, 

 constitute a brilliant fulfillment of this prediction. 



But, as regards the augmentation of power, the greatest 

 step hitherto made was independently taken a few years 

 ago by Dr. Werner Siemens and Sir Charles Wheats tone. 

 Through the application of their discovery a machine 

 endowed with an infinitesimal charge of magnetism may, 

 by a process of accumulation at compound interest, be 

 caused so to enrich itself magnetically as to cast by its 

 performance all the older machines into the shade. The 

 light now before you is that of a small machine placed 

 downstairs, and worked there by a minute steam-engine. 

 It is a light of about 1,000 candles; and for it, and for the 

 steam-engine that works it, our members are indebted to 

 the liberality of Dr. W 7 illiam Siemens, who in the most 

 generous manner has presented the machine to this Insti- 

 tution. After an exhaustive trial at the South Foreland, 

 machines on the principle of Siemens, but of far greater 

 power than this one, have been recently chosen by the 

 Elder Brethren of the Trinity House for the two light- 

 houses at the Lizard Point. 



Our most intense lights, including the six-wick lamp, 

 the Wigham gas-light, and the electric light, being in- 

 tended to aid the mariner in heavy weather, may be 

 regarded, in a certain sense, as fog-signals. But fog, when 

 thick, is intractable to light. The sun cannot penetrate 

 it, much less any terrestrial source of illumination. Hence 

 the necessity of employing sound-signals in dense fogs. 

 Bells, gongs, horns, whistles, guns, and syrens have been 

 used for this purpose: but it is mainly, if not wholly, with 

 explosive signals that we have now to deal. The gun has 

 been employed with useful effect at the North Stack, near 

 Holy head, on the Kish Bank near Dublin, at Lundy 

 Island, and at other points on our coasts. ' During the 

 long, laborious, and I venture to think memorable series of 

 observations conducted under the auspices of the Elder 

 Brethren of the Trinity House at the South Foreland in 

 ]87^ and 1873, it was proved that a short 5|-inch howitzer, 

 firing 3 Ibs. of powder, yielded a louder report than a long 

 18 pounder firing the same charge. Here was a hint to be 

 acted on by the Elder Brethren. The effectiveness of the 

 sound depended on the shape of the gun, and as it could 

 uot be assumed that in the howitzer we had hit accident- 



