248 FROM NEBULA TO NEBULA 



And on p. 244 he adds : 



When I tried these different ideas, I concluded that the 

 particles (in the corona) were behaving as a fountain behaves, 

 being both shot up and falling down again * * * My conclusion is 

 that there are a large number of solid particles in the corona, be- 

 cause there is a great deal of polarized light; and other astrono- 

 mers have found the same thing. 



So much for the superficial eruptions, but what of 

 those more deeply seated! The cycles of these are natur- 

 ally longer ; all the more severe too, for that very reason. 

 Late researches have led to the knowldge that the " solar 

 constant ' ' is not so constant after all, but varies rhythmi- 

 cally by periods of five days, of ten days, and so on, prov- 

 ing the occurrence of fluctuations in the sun himself. 

 All of these variations are easily accounted for by postu- 

 lating a series of eruptive levels, each with its own char- 

 acteristic interval of manifestation. 



THE SUET-SPOTS 



One of the periods of which we have been speaking 

 is, of course, that of the sun-spots. In this phenomenon 

 we have an example of sufficient distinctness and legibil- 

 ity to enable us, by a close study of available data, to 

 determine the solar level from which it emanates. This 

 is not exactly an easy task, for the reason that, as before 

 stated, the blast carries before it in its ascent vast quanti- 

 ties of miscellaneous debris from all of the superior 

 layers which requires to be differentiated out. The test, 

 of course, consists in discovering which is the most re- 

 fractory element or group of elements most conspicu- 

 ously represented in the pertinent spectra; and a good 

 deal also depends upon the age of the spot at the time 

 the spectra are obtained. 



Some may infer that I mean that these deep-seated 

 blasts occur sporadically, and without any preliminary 

 preparation of the surface. I do not mean this especi- 

 ally, though I admit the possibility of such happenings. 

 The time being ripe for the coming event, I presuppose, 

 rather, a series of eruptions, from the top layer to the 



