130 PLEASANT WAYS IN SCIENCE. 



and lastly, the object has ceased to give any perceptible 

 light, other than that belonging to this nitrogen line. 



Now it cannot, I think, be doubted that, accompanying 

 the loss of lustre in this orb, there has been a correspond- 

 ing loss of heat The theory that all the solid and liquid 

 materials of the orb have been vaporized by intense heat, 

 and that this vaporization has caused the loss of the star's 

 light (as a lime-light might die out with the consumption 

 of the lime, though the flame remained as hot as ever), 

 is opposed by many considerations. It seems sufficient to 

 mention this, that if a mass of solid matter, like a dead 

 sun or planet, were exposed to an intense heat, first raising 

 it to incandescence, and eventually altogether vaporizing 

 its materials, although quite possibly the time of its intensest 

 lustre might precede the completion of the vaporization, 

 yet certainly so soon as the vaporization was complete, 

 the spectrum of the newly vaporized mass would show 

 multitudinous bright lines corresponding to the variety of 

 material existing in the body. No known fact of spec- 

 troscopic analysis lends countenance to the belief that a 

 solid or liquid mass, vaporized by intense heat, would shine 

 thenceforth with monochromatic light 



Again, I think we are definitely compelled to abandon 

 Vogel's explanation of the phenomena by Zollner's theory. 

 The reasons which I have urged above are not only 

 strengthened severally by the change which has taken place 

 in the spectrum of the new star since Vogel observed it, but 

 an additional argument of overwhelming force has been 

 introduced. If any one of the suns died out, a crust form- 

 ing over its surface and this crust being either absolutely 

 dark or only shining with very feeble lustre, the sun would 

 still in one respect resemble all the suns which are spread 

 over the heavens it would show no visible disc, however 

 great the telescopic power used in observing it If the 

 nearest of all the stars were as large, or even a hundred 

 times as large, as Sirius, and were observed with a tele- 

 PCOUC of ten times greater magnifying power than any yet 



