KECENT EXPERIMENTS ON FOG-SIGNALS. 255 



desirous of discovering new facts and new relations de- 

 pendent on magneto-electric induction than of exalting 

 the force of those already obtained, being assured that 

 the latter would find their full development hereafter.' 

 The labours of Holmes, of the Paris Alliance Company, 

 of Wilde, and of Gramme, constitute a brilliant fulfil- 

 ment 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 

 Wheatstone. Through the application of their dis- 

 covery a machine endowed with an infinitesimal charge 

 of magnetism may, by a process of accumulation at 

 compound interest, be caused so to enrich itself mag- 

 netically 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 

 1000 candles ; and for it, and for the steam-engine that 

 works it, our members are indebted to the liberality of 

 Dr. William Siemens, who in the most generous manner 

 has presented the machine to this Institution. 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 

 intended 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 illumi- 

 nation. Hence the necessity of employing sound-signals 

 in dense fogs. Bells, gongs f horns, whistles, guns, and 



