ELECTRIC LIGHT FOR STEAMSHIPS. 721 



ter of a mile distant upon the neighboring walls. The same light, at 

 two feet from the reflector, darkened ordinary sensitized photographic 

 paper as much in twenty seconds as the direct rays of the sun at noon 

 on a clear day in March in one minute" (Ferguson's "Electricity"). 

 With a ten-inch quantity armature, Mr. Wild succeeded in melting 

 an iron rod fifteen inches long and one-quarter inch thick. The entire 

 machine by which this was accomplished was under five feet in length 

 and height, was only twenty inches wide, and weighed a ton and a 

 half. The Ladd engine dispenses with the use of permanent steel 

 magnets, and is a more compact form of the machine than Wild's. 

 The Gramme machine returns again to the use of powerful steel mag- 

 nets, between the poles of which revolves a ring-shaped electro-mag- 

 net. The problem of producing the best machine for the production 

 of electricity by mechanical power is not yet solved. The machines 

 now before the public will doubtless be very much improved. At 

 present, however, the means to attain the sought-for ends seem to be 

 limited. There are not many combinations which can be made. A 

 field of magnetic force being given, the question arises. What is the 

 most economical means of cutting the greatest number of lines of 

 force of the greatest intensity in the unit of time ? With the most 

 improved forms of the magneto-electric machine, we are, however, in a 

 condition to produce an electric light of a reasonable degree of con- 

 stancy and cheapness. If it is a desideratum that steamships should 

 be provided with more powerful lights than those now in use, the 

 electric light is the one to which attention is naturally directed. The 

 first points to be considered are in relation to its cost, its constancy, 

 and readiness of adjustment, and its efficiency in penetrating fogs. 

 The light-house service of Great Britain and France afiTords the only 

 experience on these points. 



The electric light has been tried by Great Britain at Dungeness, 

 and by the French Government at La Heve. The source of the light 

 in both instances was a magneto-electric machine. A force of one 

 and a quarter horse-power was required to drive the British machine, 

 and one and a half the French. Tlie descriptions of these machines 

 show that they were extremely bulky, compared with the more im- 

 proved forms, like Ladd's and the Gramme machine. The observa- 

 tions on the lights at La Heve are especially interesting, because they 

 aftbrded a means of comparison between the fog-penetrating power 

 of the electric light and the ordinary oil-light of light-houses. There 

 were two light-houses at La Heve, one of which was provided with an 

 electric light, and the other with an oil-light. The electric light was 

 equivalent to 3,500 Carcel-burners. The oil-light had an intensity of 

 630 Carcel-burners. 



" In foggy weather, in the hundred times of observation, the elec- 

 tric light was seen twice as often as the oil-light, or more. When 

 the intensity of the electric light, compared with that of the oil-lamp 



VOL. T. — 46 



