. \ontirr «/<■ hfihifiiv 



Figure 40. — Results of Le Roux's study of the relation between the speed of 

 rotation and the voltage (open circuit) for varying numbers of coils on the 

 armature of an Alliance generator. From F. P. Le Roux, "Etudes sur les 

 machines magneto-electriques," Archives des sciences physiques et nalurelles, 

 1856, vol. 33, figs. 1-3 (following p. 263). 



proved itself to be electrically and mechanically 

 superior. In addition to being cheaper as well as 

 less bulky, the Siemens dynamo could produce 

 twice as many candles per horsepower as its best 

 magneto competitor. By examining the tabulation, 

 the respective proportions of the Holmes magneto 

 and the Siemens dynamo can be seen to be as follows: 

 bulk, 114 to 1; weight, 28 to 1; total light produced, 

 1 to 5; light produced per horsepower, 1 to 4; cost 

 per unit of light, 9 to 1. Obviously, the magneto 

 generator could not compete with the new dynamo 



generator, and Trinity House decided to install 

 the Siemens dynamo instead of the Holmes generator 

 at Lizard Point. 



Hippolyte Fontaine, of the Gramme firm, protested 

 to the editor of Engineering that the trials were unfair, 

 since the Gramme machine used in the tests was the 

 1874 model rather than the new type cT atelier (actually, 

 the company had refused to submit a model). Fon- 

 taine quoted Tresca — who had tested the new Gramme 

 machine — as having found that 2 hp. produced 

 7,000 candles. Fontaine further went on to describe 



PAPER 30: DEVELOPMENT OF ELECTRICAL TECHNOLOGY IN THE 19TH CENTURY: m 



367 



