456 FRAGMENTS OF SCIENCE 



of Holmes, however, was rapidly distanced by the safer 

 and more powerful machines of Siemens and Gramme. 



As regards lighthouse illumination, the next step for- 

 ward 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 Corn- 

 wall, 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 al- 

 ternating currents. The light of the latter was of the 

 same intensity in all azimuths; that of the former was 

 different in different azimuths, the discharge being so reg- 

 ulated as to yield a gush of light of special intensity in 

 one direction. The following table gives in standard can- 

 dles the performance of the respective machines: * 



Name of Machine Maximum Minimum 



Holmes 1,523 1,523 



Alliance 1,953 1,953 



Gramme (No. 1) 6,663 4,016 



Gramme (No. 2) 6,663 4,016 



Siemens (Large) 14,818 8,932 



Siemens (Small, No. 1) ... 5,539 3,339 



Siemens (Small, No. 2) . . . 6,864 4,138 



Two Holmes's coupled . . . 2,811 2,811 



Two Gramme's (Nos. 1 and 2) . . 11,396 6,869 



Two Siemens' (Nos. 1 and 2) . . 14,134 8,520 



1 Observations from the sea on the night of November 21, 1876, made the 

 Gramme and small Siemens practically equal to the Alliance. But the photo- 

 metric observations, in which the external resistance was abolished, and previous 

 to which the light-keepers had become more skilled in the management of the 

 direct current, showed the differences recorded in the table. A close inspection 

 of these powerful lights at the South Foreland caused my face to peel, as if it 

 had been irritate,! by an Alpine sun. 



