434 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, endeav- 

 oured to turn this discovery to account for lighthouse 

 purposes. Already, in the spring of 1869, he had con- 

 structed a machine which, though hampered with de- 

 fects, exhibited 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 ob- 

 servatory at Charlton, on the opposite side of the 

 Thames. Falling upon the suspended haze, the light 

 illuminated the atmosphere for miles all round. Any- 

 thing so sunlike in splendour had not, I imagine, been 

 previously witnessed. The apparatus of Holmes, how- 

 ever, was rapidly distanced by the safer and more pow- 

 erful 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 de- 

 livered direct currents, while those of Holmes and 

 the Alliance Company delivered alternating currents. 

 The light of the latter was of the same intensity in 

 all azimuths; that of the former was different in dif- 

 ferent azimuths, the discharge being so regulated as 

 to yield a gush of light of special intensity in 

 one direction. The following table gives in stand- 



