MEMOIR IV.] CONDITION OF THE SUN'S SURFACE. 31 



MEMOIR IV. 



ON THE NATURE OF FLAME AND ON THE CONDITION OF 

 THE SUN'S SURFACE. 



From the American Journal of Science and Arts, Second Series, Vol. XXVI., 1858 ; 

 Philosophical Magazine, Feb., 1858. 



CONTENTS: Dove's experiments on electric light. Dark lines replaced 

 by bright ones. Electric spark between metallic surfaces. The lines 

 depend on the chemical nature of the substance from which the light is- 

 sues. They may be used for determining the physical condition of the 

 sun and stars. Three hypotheses of the condition of the surfs surface 

 examined. 



AMONG the more recent publications on Photo-chem- 

 istry, there is one by Professor Dove on the electric light 

 (Philosophical Magazine, Nov., 1857) which will doubt- 

 less attract the attention of those interested in that 

 branch of science. Examination by the prism, and by 

 absorbing and reflecting colored bodies, leads him to the 

 conclusion that it is necessary to consider the luminous 

 appearance as having two distinct sources: 1st, the igni- 

 tion or incandescence of the material substances bodily 

 passing in the course of the discharge ; 2d, the proper 

 electrical light itself. As respects the former, he illus- 

 trates its method of increase from low to high tempera- 

 tures by supposing a screen to be withdrawn from the 

 red end of the spectrum through the colored spaces suc- 

 cessively towards the violet ; and that of the latter from 

 the bluish brush to the bright Leydeii spark, by a like 

 screen drawn from the violet towards the red. 



The true electric light exhibits properties resembling 

 those observed in actual combustions, as though there 



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