RECENT SOLAR RESEARCHES. 83 



ward nearly a century ago by Sir William Herschel. 

 That thoughtful observer recognised in the solar photo- 

 sphere a widely-extended layer of luminous clouds, 

 while he regarded the light of the penumbrae of sun- 

 spots as coming from a lower cloud-layer. He con- 

 ceived that up-rushes of vapour, thrusting aside both 

 layers, caused the appearance of a solar spot. We have 

 heard a great deal lately of the English and Conti- 

 nental theories of the solar constitution ; but the 

 evidence we have recently obtained goes far to show 

 that, after all, Sir William Herschel, without the aid 

 of spectroscope or polariscope, formed a juster view of 

 the solar constitution than any which has been recently 

 propounded. He was doubtless mistaken in the view 

 (which he put forward as a mere hypothesis) that the 

 real surface of the sun may be not very intensely 

 heated. We have every reason to believe that the 

 whole mass of the sun is raised to an inconceivable 

 degree of heat. But for the rest, there seems far more 

 reason to believe in Sir William Herschel's cloud- 

 layer theory than in any other which has been put 

 forward in recent times. 



Let us consider some of the consequences of such a 

 constitution. Imagine the ascent of vapours of many 

 elements from the fluid surface of the solar oceans. 

 This mixed atmosphere is in reality aglow with the 

 intensest heat and light, so that if we could examine 

 its spectrum separately, we should see the bright lines 

 of the various vaporous elements which constitute it. 

 But intensely hot as it is, it must yet be less hot than 



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