for the year 1870. xxix 



From the observations of Lockyer, Huggins, Janssen, 

 and others, it appears that surrounding the photosphere is 

 an envelope of far less luminosity, vf'hich has been styled 

 the chromosphere. The spectra of this chromosphere is, 

 with the exception of a yellow hne, identical with that of 

 hydrogen, and like that of the red prominences. The 

 spectra of magnesium and barium were also observed 

 occasionally in the chromosphere, as if injected into it from 

 the photosphere. From this it may be inferred that the 

 hydrogen flames or red prominences are portions of the 

 chromosphere thrust out into space by eruptive forces from 

 beneath. 



The spots on the sun have also been the subject of 

 unceasing inquiry, both as to their constitution, their cause, 

 and the mysterious influence they appear to exert on the 

 magnetic and electrical condition of the earth and air. The 

 opinion seems to have gained ground that they are down- 

 rushes, cyclones, or maelstroms, by which the light-bearing 

 vapours of the photosphere are whirled or sucked into 

 enormous depressions laying bare a cooler or more light- 

 absorbing substratum. These spots, as you are aware, are 

 more prevalent during some years than others, and it is now 

 pretty well established that the maximum period recurs 

 about every 10'6 years. 



It is also found that the maximum disturbances of 

 terrestrial magnetism, or periods when magnetic storms 

 become prevalent, take place at the time of the sun-spot 

 maximum, and at such times frequent and very bright 

 auroras occur. At this present moment the sun is passing 

 through one of its '' spotted fevers," and the magnificent 

 aurora, with the magnetic storm which preceded and 

 accompanied it, was one of those 'wonderful sympathetic 

 shudders by which our globe testifies its subordination to 

 solar forces. 



