162 



SCIENCE. 



I Vol.. I., No. 



the intensit3' still more. In a scintillating light 

 with red and white flashes there is an intensitj^ 



of 60,000 carcels with the Alliance, and 110^- 

 000 carcels with the Gramme machine ; with 

 a scintillating light with groups of white flash- 



es, 90,000 carcels for the former, and 150,000 

 carcels with the latter. The intensities with 

 the de Meritens machine are about the same 

 as with the Gramme ; and 125,000 carcels may 

 be taken as the average intensitj- when the 

 electric light is used. 



Some details will now be given of the in- 

 stallations actuallj^ existing, and of those in 

 process of construction ; specially describing 

 the lights of la H6ve, the first in date to be 

 electricall}' lighted, and the Planier light, 

 whose installation has just been completed. 



The lights of la Hfeve, situated on the cape 

 of this name and on the top of the cliff, are, 

 from this fact, verj' elevated : so the towers 

 themselves are not of great height. Both 



towers are square, and are j)lac'ed abotit sixty 

 metres apart ; between them being the long 

 building containing the steam-power, genera- 

 tors, and quarters for the keepers. 



There are four Alliance machines, — two for 

 each light. The two on the left supply the left- 

 hand tower ; and the two on the right, the 

 tower on the right hand. The conductors lead- 

 ing the current from the generator are first 

 thick copper rods connected with the commu- 

 tator. Fig. 2. The rod A communicates with 

 the two similar poles of the two machines, 

 the rods B and B' being connected to the op- 

 posite poles. Ordinarily- one machine supplies 

 each light. Thus the current arrives by A, 



