RECENT EXPERIMENTS ON FOG-SIGNALS. 255 



1831, ' been desirous of discovering new facts and new 

 relations dependent on magneto-electric induction 

 than of exalting the force of those already obtained, 

 being assured that the latter would find their full de- 

 velopment hereafter.' The labours of Holmes, of the 

 Paris Alliance Company, of Wilde, and of Gramme, 

 constitute a brilliant fulfilment 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 

 1,000 candles; and for it, and for the steam-engine 

 that works it, our members are indebted to the liberal- 

 ity 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, ma- 

 chines 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 

 illumination. Hence the necessity of employing sound- 

 signals in dense fogs. Bells, gongs, horns, whistles, 



