

xxii.] THE HYPOTHESES CONTRASTED. 307 



3. The spectra of prominences should The spectra of prominences should 

 consist of lines familiar to us in our even be in many cases unfamiliar, be- 

 laboratories, and should have the same cause prominences represent what is 

 intensities, because solar and terres- going on at a temperature hot enough 

 trial elements are the same. to prevent the coming together of the 



atoms of which our chemical elements 

 are composed. 



FACT. When we leave out of consideration the lines of hydro- 

 gen, calcium, magnesium, and sodium, which are seen in 

 the hottest stars, most of the lines are either of unknown 

 origin or are feeble lines in the spectra of known elements. 

 See p. 185. 



4. Qud the same element the lines Qud the same element the lines 

 widest in spots should always be the widest in spots should vary enor- 

 same. mously, because the absorbing material 



is likely to originate in and to be 

 carried to different depths. 



FACT. There is immense variation, as will be seen in the sequel. 



5. The spectrum of iron in a pro- The spectrum of iron in a promi- 

 mrnence should be the same as the nence should be vastly different from 

 spectrum of iron in a sun-spot. the spectrum of iron in a sun-spot 



because the spot is cooler than the 

 prominence. 



FACT. The spectra, as will be seen in the sequel, are as 

 dissimilar as those of any two elements. 



6. The spectra of spots and promi- The spectra should vary, because 

 nerices should not vary with the sun- the sun is hotter at maximum. 



spot period. 



FACT. They do vary, as will be shown in the sequel. 



7. Motion in the iron vapour, e.g. Motion should be unequally indi- 

 in a spot or a prominence, should be cated, because the lines are due to 

 indicated by the contortion of all the divers constituents which exist in dif- 

 irori lines equally. ferent strata according as they can 



resist the higher temperatures of the 

 interior regions. 



FACT. The indications show both rest and motion. See post, 



chap. xxiv. 



From the above sketch, hasty though it be, it is, I think, easy 

 to gather that the new view includes the facts much better than 



x 2 



