436 FRAGMENTS OF SCIENCE. 



electricity to enter the lists as the rival of our present 

 means of illumination. 



Soon after the announcement of their discovery by 

 Siemens and Wheatstone, Mr. Holmes, at the instance 

 of the Elder Brethren of the Trinity House, endeavoured 

 to turn this discovery to account for lighthouse purposes. 

 Already, in the spring of 1869, he had constructed a 

 machine which, though hampered with defects, exhi- 

 bited extraordinary power. The light was developed 

 in the focus of a dioptric apparatus placed on the 

 Trinity Wharf at Blackwall, and witnessed by the Elder 

 Brethren, Mr. Douglass, and myself, from an observatory 

 at Charlton, on the opposite side of the Thames. Falling 

 upon the suspended haze, the light illuminated the 

 atmosphere for miles all round. Anything so sunlike 

 in splendour had not, I imagine, been previously 

 witnessed. The apparatus of Holmes, however, was 

 rapidly distanced by the safer and more powerful 

 machines of Siemens and Gramme. 



As regards lighthouse illumination, the next step 

 forward was taken by the Elder Brethren of the Trinity 

 House in 1876-77. Having previously decided on the 

 establishment of the electric light at the Lizard in 

 Cornwall, they instituted, at the time referred to, an 

 elaborate series of comparative experiments wherein 

 the machines of Holmes, of the Alliance Company, of 

 Siemens, and of Gramme, were pitted against each 

 other. The Siemens and the Gramme machines 

 delivered direct currents, while those of Holmes 

 and the Alliance Company delivered alternating 

 currents. The light of the latter was of the same in- 

 tensity in all azimuths ; that of the former was 

 different in different azimuths, the discharge being 

 so regulated as to yield a gush of light of special 

 intensity in one direction. The following table gives 



