222 Prof. Faraday, on the Electric Light. [March 9, 



money it can be raised to a five or tenfold power, or more, and will 

 then give five or tenfold effect. This can be done, not merely without 

 increase of the volume of the light, but whilst the light shall have a 

 volume scarcely the 2000th part of that of the oil flame. Hence, the 

 extraordinary assistance we may expect to obtain of diminishing the 

 size of the optical apparatus and perfecting that part of the apparatus. 



Many compressed intense lights have been submitted to the 

 Trinity-house ; and that corporation has shown its great desire to 

 advance all such objects and improve the lighting of the coast, by 

 spending, upon various occasions, much money and much time for this 

 end. It is manifest that the use of a lighthouse must be never failing, 

 its service ever sure ; and that the latter cannot be interfered with by the 

 introduction of any plan, or proposition, or apparatus, which has not 

 been developed to the fullest possible extent, as to the amount of light 

 produced, — the expense of such light, — the wear and tear of the appara- 

 tus employed, — the steadiness of the light for 16 hours,— its liability 

 to extinction, — the amount of necessary night care, — the number of 

 attendants, — the nature of probable accidents, — its fitness for secluded 

 places, and other contingent circumstances, which can as well be ascer- 

 tained out of a lighthouse as in it. The electric spark which has been 

 placed in the South Foreland High Light, by Professor Holmes, to do 

 duty for the six winter months, had to go through all this preparatory 

 education before it could be allowed this practical trial. It is not 

 obtained from frictional electricity, or from voltaic electricity, but from 

 magnetic action. — The first |spark (and even magnetic electricity as a 

 whole) was obtained 28 years ago. (Faraday, Philosophical Transactions, 

 1832, p. 32.) If an iron core be surrounded by wire, and then moved 

 in the right direction near the poles of a magnet, a current of electri- 

 city passes, or tends to pass, through it. Many powerful magnets 

 are therefore arranged on a wheel, that they may be associated very 

 near to another wheel, on which are fixed many helices with their 

 cores, like that described. Again, a third wheel consists of magnets 

 arranged like the first ; next to this is another wheel of the helices, and 

 next to this again a fifth wheel, carrying magnets. All the magnet- 

 wheels are fixed to one axle, and all the helix wheels are held immoveable 

 in their place. The wires of the helices are conjoined and connected 

 with a commutator, which, as the magnet-wheels are moved round, 

 gathers the various electric currents produced in the helices, and 

 sends them up through two insulated wires in one common stream of 

 electricity into the lighthouse lanthorn. So it will be seen that nothing 

 more is required to produce the electricity than to revolve the magnet- 

 wheels. There are two magneto-electric machines at the South Fore- 

 land, each being put in motion by a two-horse power steam-engine ; 

 and, excepting wear and tear, the whole consumption of material to 

 produce the light is the coke and water required to raise steam for the 

 engines, and carbon points for the lamp in the lanthorn. 



The lamp is a delicate arrangement of machinery, holding the two 

 carbons between which the electric light exists, and regulating their 



