Applicability of the Electric Light to Lighthouses. 329 



electricity is restored to its original form of light, in its passage 

 between the charcoal points of the electric lamp. It is equally 

 easy to trace the changes which take place, when the motion 

 of the magneto-electric apparatus is produced by muscular force,, 

 instead of by the steam-engine. 



It is not necessary to use permanent magnets, in the de- 

 velopment of electricity by means of induction. Recent experi- 

 ments by Mr. Siemens show that the permanent magnets may 

 be replaced, in such experiments, by electro-magnets. And 

 he even believes that such a substitution would be advantageous, 

 under the supposition that the permanent magnets become im- 

 paired in power, by use in this way. But both the French and 

 English official experiments on the applicability of the electric 

 light to lighthouses, have shown the contrary to be the fact. 



Wilde's magneto- electric machine is intermediate between 

 the ordinary magneto-electric machine and that suggested by 

 Siemens's experiments. It is constructed on a principle long 

 since brought forward by M. Seguin the elder. In Wilde's 

 apparatus, electricity is produced by permanent magnets, in an 

 armature which is an electro-magnet of a peculiar form, and is 

 made to revolve rapidly. The electric current, thus generated, 

 in the armature, is used to excite a system of electro-magnets ; 

 and these develope a more intense current in a second electro- 

 magnetic armature, which also revolves rapidly. This second 

 current is used to excite a second system of electro-magnets ; 

 and these develope a still more intense and extremely powerful 

 current in a third electro-magnetic armature ; which, like the 

 others, revolves rapidly. Each armature makes about three 

 thousand revolutions in a minute ; and it is the wear and tear 

 which must arise from heavy masses moving with so high a 

 velocity that constitutes the great objection to this very in- 

 genious and most powerful machine. 



Mr. Holmes's apparatus was transferred from the South 

 Foreland to Dungeness, in 1862. It was fixed over an oil lamp 

 apparatus, lest any accident should render it incapable of being- 

 used. The Elder Brethren of the Trinity House refuse to 

 sanction the use of the electric light, unless when, in case of 

 its failure from any cause, it can be instantly replaced by the 

 ordinary oil apparatus. Moreover, with the electric light, a 

 duplicate of every portion of the apparatus is required, lest any 

 of it should get out of order. 



The apparatus at Dungeness consists of one hundred and 

 twenty permanent magnets of about fifty pounds each, ranged 

 on the periphery of two large wheels. One hundred and sixty 

 soft iron cores, surrounded by coils of insulated wire, are made 

 to revolve past the magnets one hundred times in a minute, by 

 steam power. The streams of electricity, thus produced, are 



