112 ELECTRIC LIGHTING. 



of great importance, and this has been so well understood 

 that at various times there have been instituted experiments 

 upon it more or less conclusive. As early as 1855 Ed. 

 Becquerel had made an important investigation on batteries 

 as regards this point, and the work was continued by Tresca 

 at the Conservatoire des Arts et Metiers with the magneto- 

 electric machines of the Alliance Company. At a later period 

 these machines were the subject of laborious investigations, 

 conducted by Reynaud and Degrand at the Directory of 

 Lighthouses. A more profound study of the question was 

 undertaken by Le Roux in 1865, and this was the subject of 

 a very interesting communication printed in the Bulletin de 

 la Societe d' Encouragement (tome XIV., page 699). Jamin, in 

 .conjunction with Rogers, examined from a scientific point of 

 view the work produced by the same machines, and in 1877 

 Tresca, in a paper read before the Acadetnie des Sciences, gave 

 a complete investigation of the effects produced by the 

 Gramme machine. At length the success of these machines, 

 and of their application to lighthouses, so much attracted the 

 attention of the English that in 1877 they considered it 

 necessary to appoint a Commission of Inquiry to examine 

 this question. This Commission was composed of Tyndall, 

 Douglass, Sabine, Edwards, Drew-Atkings, and Minster, with 

 Douglass as reporter ; and it shortly afterwards published a 

 Report, known as The Report of the Trinity House on the 

 South Foreland Lighthouse, and this was for some time re- 

 garded as the best authority on the subject. The Americans, 

 however, were also desirous of examining the question, and 

 the Franklin Institute, after an invitation to the makers of 

 machines to compete, which was responded to by only three, 

 appointed a Commission composed of Briggs, Rogers, Chase, 

 Houston, Thomson, Rand, Jones, Sartain, and Knight, and 

 this Commission, subdivided into three committees, presented 

 a double report, which was published in the Bulletin of the 

 Franklin Institute. We shall give the numerical results from 

 this report after those of the English Commission 



