S8 YEAR-BOOK OF FACTS. 



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 apparatus 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 ascertained 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 elec- 

 tricity, or from voltaic electricity, but from magnetic action. The 

 first spark (and even magnetic electricity as a whole) was obtained 

 twenty-eight years ago. (Faraday, Plniosvphkal Transactions, 1S32, 

 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 electricity 

 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 ar- 

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

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

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

 moveable 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 lantern. 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 Foreland, 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 lantern. 



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

 carbons between which the electric light exists, and regulating their 

 adjustment ; so that whilst they gradually consume away, the place 

 of the light shall not be altered. The electric wires end in the two 

 bars of a small railway, and 11)1011 these the lamp stands. When the 



carbons of a lamp are nearly gone, that lamp La lilted oil' and another 



instantly pushed into its plaOO. The machines and lamp have done 

 their duty daring the past sis months in a real and practical manner. 

 The light has never gone out through any deficiency or cause in the 

 engine and machine house: and when it has become extinguished in 

 the lantern, a single touch of the keeper's hand has set it shining 

 as bright as ever. The light shone up and down the Channel, and 



