124 PLEASANT WAYS IN SCIENCE. 



much less light or none at all. Through a sudden and 

 violent tearing up of this stratum, the interior incandescent 

 materials which it encloses must naturally break forth, and 

 must in consequence, according to the extent of their erup- 

 tion, cause larger or smaller patches of the dark envelope 

 of the body to become luminous again. To a distant ob- 

 server such an eruption from the hot and still incandescent 

 interior of a heavenly body must appear as the sudden 

 (lashing-up of a new star. That this evolution of light 

 may under certain conditions be an extremely powerful 

 one, could be explained by the circumstance that all the 

 chemical compounds which, under the influence of a lower 

 temperature, had already formed upon the surface, are again 

 decomposed through the sudden eruption of these hot 

 materials ; and that this decomposition, as in the case of 

 terrestrial substances, takes place under evolution of light 

 and heat. Thus the bright flashing-up is not only ascribed 

 to the parts of the surface which through the eruption of the 

 incandescent matter have again become luminous, but also 

 to a simultaneous process of combustion, which is initiated 

 through the colder compounds coming into contact with the 

 incandescent matter." 



Vogel considers that Zollner's hypothesis has been con- 

 firmed in its essential points by the application of spectrum 

 analysis to the stars. We can recognize from the spectrum 

 different stages in the process of cooling, and in some of the 

 fainter stars we perceive indeed that chemical compounds 

 have already formed, and still exist. As to new stars, again, 

 says Vogel, Zollner's theory seems in nowise contradicted 

 " by the spectral observations made on the two new stars of 

 1866 and 1876. The bright continuous spectrum, and the 

 bright lines only slightly exceeding it at first " (a description, 

 however, applying correctly only to the star of 1876), "could 

 not be well explained if we only suppose a violent eruption 

 from the interior, which again rendered the surface wholly 

 or partially luminous ; but are easily explained if we suppose 

 that the quantity of light is considerably augmented through 



