160 ON THE OKIGIN OF THE PLANETARY SYSTEM. 



oblique direction. Fig. 11 represents in A to E the 

 different aspects of such a spot as it comes near the 

 edge of the sun. 



Just on the edge of these spots there are spectro- 

 scopic indications of the most violent motion, and 

 in their vicinity there are often large protuberances ; 

 they show comparatively often a rotatory motion. 

 They may be considered to be places where the 

 FIG. 11. 





* 



cooler gases from the outer layers of the sun's atmos- 

 phere sink down, and perhaps produce local superficial 

 coolings of the sun's mass. To understand the origin 

 of these phenomena, it must be remembered that the 

 gases, as they rise from the hot body of the sun, are 

 charged with vapours of difficultly volatile metals, 

 which expand as they ascend, and partly by their ex- 

 pansion, and partly by radiation into space, must be- 

 come cooled. At the same time, they deposit their 



