Except, however, in the case of short distances, or with telegraphs belonging to private persons or commercial firms, these instruments
have not met with very general adoption. This is owing to the great tension of the induced current, and the consequent difficulty of insulating the wire, particularly for long distances, objections from which the old galvanic apparatus is in a much greater measure free. Mr Henley was the first to use the dynamic magneto-electric machine for working the electric telegraph soon after this instrument had been adopted in England; but as we have seen, the method, except in the cases quoted, have been in great measure abandoned. A large magneto-electric machine has lately been invented by Wheatstone, the induced spark from which is used for firing mines.
The first electro-magnetic machine used for lighting purposes appears to have been one that was the joint invention of MM. Nollet and Van Malderen, of Brussels, a circumstance to which it probably owes its name of the ‘Alliance Machine.’
Nollet, who brought out his invention (which is a modification of Clarke’s) in 1850, originally designed it for the electrolysis of water, the hydrogen resulting from which it was proposed to pass through camphine, or some other hydro-carbon illuminant, and to burn as gas. Additionally it was designed to use the hydrogen as a source of motive power by exploding it in a suitably constructed engine. Owing to the improvements, however, effected in the machine by Van Malderen, by which it became a powerful generator of magneto-electricity, this purpose was abandoned. ‘The Alliance Machine’ consists of a cast-iron frame, on the circumference of which 40 powerful horseshoe magnets, each capable of supporting a weight of 120 to 130 lbs., are fixed, in eight series of 5 magnets each. A number of circular metal discs, around the circumference of which are attached sixteen bobbins of insulated wire fixed to a horizontal shelf turned by a pulley, are in such a position with regard to the magnets, that with each revolution of the shaft each bobbin passes sixteen alternate poles of the magnets, and will have had sixteen alternate currents set up or induced in it. Until replaced by the later and smaller magneto-electric machine, the ‘Alliance’ has been the one mostly employed for the production of the electric light in France, and it is still in use in the lighthouses of Hève and Grisnez, as well as in those of many other places in that country. In 1856 Mr Holmes took out a patent for a machine, which differs from Nollet’s in increasing the number of bobbins by arranging them in concentric circles between two brass discs. By this device the bobbins revolve more quickly in succession in front of the poles of the magnets, a plan which ensures the generation of a greater number of currents for every revolution.
Like the first application of Nollet’s, Holmes’ machine was used for lighthouse illumination. It was in work from December,
1858, until June, 1862, at the South Foreland lighthouse, since which time it has been removed to Dungeness, in the lighthouse of which station it has been in use ever since.
When applied to lighting purposes, both the ‘Alliance’ and Holmes’, and the other machines named, are worked in conjunction with the carbon points, which when arranged with proper machinery constitute the electric lamp.
Wild’s and Ladd’s are powerful dynamic magneto-electric instruments, capable of yielding large quantities of the electric fluid.
Artificial illumination by means of electricity has, however, been more or less occasionally practised for other than lighthouse purposes.
For instance, in 1854, during the building of the Napoleon Docks at Rouen, when 800 workmen were engaged nightly for four hours, the electric light was used for several nights with perfect success, the men being able to carry on their work at a distance of more than 100 yards from the source of the light.