1879.J on the Electric Light. 7 



irregularity aiul deterioration iji the macliinc of Holmes, was, at 

 the suggestion of M. Masson,* entirely abandoned ; alternating 

 currents instead of the direct current being employed. M. Serrin 

 modilied his excellent lamp witli the express view of enabling it^ to 

 cope with alternating currents. During the International Exhibition 

 of 1862, where the machine was shown, M. Berlioz offered to 

 dispose of the invention to the Elder Brethren of the Trinity House. 

 They referred the matter to Faraday, and he replied as follows: 

 " I am not aware that the Trinity House authorities have advanced 

 so ftir as to be able to decide whether they will require more 

 magneto-electric machines, or whether, if they should require them, 

 they see reason to suppose the means of their supply in this country, 

 from the source already open to them, would not be sufficient. 

 Therefore I do not see that at present they want to purchase a 

 machine." Faraday was obviously swayed by the desire to protect 

 the interests of Holmes, who had borne the burden and heat which 

 fall upon the pioneer. The Alliance machines were introduced with 

 success at Cape la Heve, near Havre ; and the Elder Brethren of the 

 Trinity House, determined to have the best available apparatus, 

 decided, in 1868, on the introduction of machines on the Alliance 

 principle into the lighthouses at Souter Point and the South Foreland. 

 These machines were constructed by Professor Holmes, and they 

 still continue in operation.! 



As their jircsent scientific adviser, the Elder Brethren did 

 me the honour of asking my opinion as to the course which they 

 proposed to pursue with regard to the introduction of these new 

 machines. That opinion is expressed in the following extract from 

 a report dated May 16th, 1868: "There is no doubt that elec- 

 tricity places at the disposal of the Elder Brethren a soiu'ce of 

 light next to the sun itself in power, and far transcending any 

 light obtainable from the combustion of oil. With regard to the 

 practical application of the magneto-electric light, the question, in 

 my opinion, has been solved by the performance of the machine at 

 Dungeness. That machine was one of the first, if not the very first, 

 constructed with a view to lighthouse illumination. Defects inherent 

 in first constructions were associated with the machine. If, notwith- 

 standing these defects, some of which were very grave, the interrup- 

 tions have been so few, it may be safely inferred that with our 

 augmented experience, and with the improved apparatus now within 

 our reach, the performance of the magneto-electric machine may be 

 rendered practically perfect. It is with the profound conviction that 

 the decision is a wise one that I learn the intention of the Elder 



* Du Moncel, ' 1' Electricity,' Aug. 1878, p. 150. 



t The photometric values of the lights produced by these machines were 

 determined by Mr. Douglass, whose measurements showed that they fell far 

 below the specified power. A new and very powerful macliinc being imported 

 from Paris, Mr. Holmes was required so to btrengtheu his magnets as to make his 

 machines equal to Ihosc of the "Alliance." 



