io3 



SCIENTIFIC APPARATUS. 



The electric-light is far more intense, and it more nearly 

 approaches to a point of light, as distinguished from an illumi- 

 nating surface, than the lime-light ; it requires, however, a more 

 elaborate lamp, and more skilful attention while in action. The 

 light is produced by the incandescence of carbon due to an intense 

 electric current. For this purpose 40 or 50 Grove's or Bunsen's 

 cells are generally employed. Various forms of lamp have been 

 constructed, and there still remains more to be done in this 

 -direction. The two most generally in use are, first, Serrin's, 



which is better adapted to purposes of general illumination than 

 to optical experiments, it is largely so used in France; and, 

 secondly, Foucault's Regulator as constructed by Duboscq. For 

 the battery various dynamo-electric machines have been substi- 

 tuted, such as Clarke's, Holms's, Wilde's, and latterly Gramme's, 

 which last, although the most effective, is yet in an early stage of 

 development. 



Other machines for the production of electric currents will be 

 mentioned under electricity. 



