used the same means to enable the laborers to work 

 through the night during his modernization of Paris." 



During the 1860"s the Alliance machine with a com- 

 mutator was also tried in other enterprises. An at- 

 tempt was made to use the generator instead of 

 chemical cells in the telegraph central power station 

 and it, too, was declared a success, although not as 

 complete a one as the attempt made in Prussia, "since 

 France was larger."^- In 1868, the famous Parisian 

 electroplating firm of Christofle sought to imitate 

 its competitor, the Elkington firm with its English 

 generators, by using the Alliance machine for plating. ^^ 



Some of the first experiments conducted at the 

 Sorbonne's new physical laboratory in 1868 were 

 concerned with the Alliance machine.*'^ J. C. Jamin 

 and G. Roger continued the work of Le Roux and 

 gave experimental proof for the usual assumption 

 that each coil on the disk armature was equivalent to a 

 chemical cell. The output of the generator could 

 then be calculated by applying Ohm's law to a 

 battery of cells, each of which produced a certain 

 voltage and had a certain fixed internal resistance. 

 Jamin and Roger also investigated the relationship 

 between the energy necessary to drive the generator 

 and the heat produced in the external circuit. Some 

 insight into the cost of the electric light can be 

 obtained from their finding that 100 liters of gas 

 must be consuined in the gas engine driving the 

 generator in order to maintain an electric arc at the 

 same intensity as a gas burner using one liter of gas 

 per minute. 



Before the Alliance machine gave way before the 

 superior Gramme machine (discussed below), it 

 played a role, although a minor one, in the defense 

 of Paris during the Franco-Prussian War.^^ Arc- 

 light stations were installed in the various forts 

 circling the city, and each was provided with four 

 electricians and with equipment garnered from instru- 

 ment-makers, telegraph offices, and laboratories. 



61 Journal of the Society of Arts, 1868, vol. 16, p. 826. 



62 Z,c.f Monies, 1867, vol. 15, p. 702. 



« Les Monies, 1867, vol. 13. pp. 405-406; 1868, vol. 16, p. 

 177. 



^-i Le Roux, op. cit. (footnote 87); Cosmos, 1868, vol. 2, pp 

 6-7; Jules Jamin and Gustav Roger, "Sur les Machines 

 magneto-electriqnes," Comptes rendus, 1868, vol. 66, pp. 1100- 

 1104, and "Sur les Lois de I'induction," Comptes rendus, 1868, 

 vol. 66, pp. 1250-1252. 



65 L'Annee scientifique , 1874, vol. 18, pp. 430-434; Bulletin de 

 la Societe d' Encouragement pour I' Industrie Mationale, 1870, vol. 

 17, pp. 659-665. 



Bunsen cells were used in most of these stations, but 

 the brightest light of all, at the Moulin de la Galette, 

 obtained its power from an Alliance machine. The 

 arc lights were not very effective, but they did help to 

 prevent surprise attack and to discourage sappers 

 during the night. 



When Holmes heard of the French commutatorless 

 machines, he sought to produce machines of a 

 similar type. After filing his first patent specification 

 on an alternator in 1867 (fig. 46), he filed two other 

 patents, one in 1868 and one in 1869.^* 



In 1867 Holmes constructed two alternators (fig. 47) 

 for a new lighthouse to be erected on the northeastern 

 coast of England at Souter Point, near Newcastle. 

 Before installation the new units were sent to the 

 Paris exhibition of 1867 where, at first, they failed to 

 work. Seven banks with eight permanent magnets 

 per bank and six disk-armatures with 16 electomagnets 

 per disk constituted the 3-ton machine, which was 6 

 feet long, 4 feet 4 inches wide, and 5 feet 6 inches 

 high. About 3 hp. was required to drive the machines 

 at 400 r.p.m. and to produce 1,520 cp. Almost four 

 years elapsed before the machines were in use; they 

 were first turned on in January 1 871 . But the expenses 

 were only half that at Dungeness, and, most important, 

 the lights were constantly in service. Eight years 

 later two similar machines were installed in each of 

 the two lighthouses at South Foreland.*" 



By 1882 there were five electric lighthouses in 

 England and four in France. However, not all of 

 these used the Alliance or the Holmes machines, for 

 serious competition had appeared. The lighthouse at 

 Planier used the more efficient modification of the 

 Alliance machine invented by De Meritens (fig. 48),** 

 but a still more serious competitor of the magneto 

 generators was the new dynamo generator. By the 

 time the first lighthouse dynamo was installed, in 

 the channel at Lizard Point in 1878, the dynamo gener- 

 ator already had begun to dominate in the field of 

 electric light. 



Before turning to the story of the dynamo, it might 

 be of interest to compare the performance of the two 

 magneto generators, the Alliance and the Holmes 



«« British patents 2307 (February 10, 1868), 2060 (December 

 23, 1868), and 1744 (December 3, 1869). 



6' See Douglass, op. cit. (footnote 36) and Richard, op. cit, 

 (footnote 36). 



68 French patent 123766 (April 10, 1878; additions, May 8 

 and June 26, 1878); Du Moncel, op. cit. (footnote 47), pp. 

 85-88; Engineering, 1879, vol. 28, pp. 372-373. 



362 



BULLETIN 228: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



