I 



relatively steady illumination with few breakdowns, 

 but it could be used only where unusual conditions 

 justified its high initial cost. Such conditions were 

 to be found in the French lighthouse service, where 

 it was to have more success than Holmes" machine 

 had had in England. 



When the arc light first appeared in the theater in 

 1848, the French administration of public works, 

 which was entrusted with lighthouse service, began 

 to consider the possibility of using this new form of 

 illumination. At first, that body experimented with 

 running the arc light by means of chemical cells, 

 but when the experiments of Faraday and Holmes 

 were brought to its attention in 1857, the feasibility 

 of the magnetoelectric machine was considered. 



However, no action was taken until the director of 

 the French lighthouse administration, Leonce Rey- 

 naud, and his chief engineer, E. AUard, visited Holmes' 

 installation at South Foreland in April 1859. After 

 hearing of the increased efficiency of the commutator- 

 less Alliance machine, Raynaud decided to obtain 

 one for experimentation. By the fall of 1859 the 

 Alliance machine was being tested for possible use 

 in the French lighthouse system. After careful study, 

 Reynaud submitted an extensive report early in 1863 

 on its possible brightness, the distance from which it 

 could be seen, and the economic advantages of its 

 use in a lighthouse. He found that a 6-disk machine 

 produced an arc of 180 to 190 Carcel units mean 

 intensity when driven by a 2-hp. steam engine, and 



358 



BULLETIN 228: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



