Marvels of the Universe 



497 



Photograph taten «/] 



SPOTS ON THE SUN. 



[Orecniridi Obsprvaforv. 



The same group of spots as on page 496, but seen three days later, when the rotation of the Sun had brought it near to the 

 eclge of the disc. It is therefore seen much foreshortened. The bright material of the Sun's general surface has overffo^ved. 

 and almost entirely hidden the following half of the group, but has left the leading spot almost untouched. 



which always accompany a spot are considerably brighter than the Sun itself, there is very little 

 loss of light or heat, if any, even during the greatest outbreaks that have ever been witnessed. Up 

 to the present, therefore, it has been a moot point whether the Sun sends us most light and heat in 

 years when spots are large and numerous, or in years like the present, when they are almost entirely 

 absent. At one time Sir Norman Lockyer, and other leading solar observers, held that the total 

 radiation of the Sun was greatest when there were most spots ; at the present time the opposite 

 opinion appears to be gaining ground ; but the evidence in either case is very slight and conflicting. 



But what are the spots ? The Sun itself is held to be a globe of intensely heated gases, sur- 

 rounded by a thin shell of luminous clouds where some of these gases are partially condensed as 

 they come into contact with outer space. This shell of intensely brilliant cloud is the photosphere, 

 and the granulations of the surface are the regions where such condensation is greatest and the 

 clouds thickest and most brilliant. A spot, then, is a region in which these bright photospheric 

 clouds are not able to form ; and it is very instructive to watch how the photosphere spreads itself 

 above and over a spot when this is in its declining stage. 



Many attempts have been made to trace a connection between the numbers of spots on the Sun 

 and the changes in terrestrial weather. Rainfall, hurricanes and cyclones, Indian famines, have 

 all been made the subjects of inquiry ; so far without any result that can be described as satis- 

 factory or conclusive. In this country we never have a hot summer, or a very wet or cold one, 

 without some attempt being made to foist the responsibility for it upon the solar changes. But 

 seasons of such pronounced character have happened almost indiscriminately at times when Sunspots 

 were specially numerous, and when there were none at all. 



In one direction, and as yet in one direction only, has a distinct and unmistakable connection 



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