Sun-spots. 



Although the study of the sun through optical instru- 

 ments is attended with great difficulties, nevertheless 

 there are some solar phenomena which, thanks in part to 

 skilful mechanical and other devices, in part to cosmic 

 occasional opportunities -- eclipses and so forth -- have 

 now been more or less iu\\y investigated. Amongst 

 such we must number solar protuberances and sun-spots. 

 The latter are ascribed to various causes, none of which 

 however seem demonstrable on scientific ground, appea- 

 ring rather sheer inventions than reasonable hypotheses. 

 The definite results .of observation have gone no further 

 than establishment of the two facts, firstly, that sun-spots 

 change their form, and secondl} T , that they change their 

 position. 



Imagine a furious fiery furnace the flame of which 

 spreading in more or less level rays of reddish yellou, 

 presents the form of a rounded mass of fire, and sup- 

 pose that a green branch of a tree is thrown into this 

 fire. Before burning, this bough will emit a liquid which 

 will generate a dark-coloured smoke so dense that it will 

 conceal the flame beneath it, and this dark spot resul- 

 ting from the cloud of smoke will be seen to change its 

 form as the bough begins to burn, while movements of 

 the flames beneath, owing to wind or other causes, will 

 produce a corresponding change in the position of the 

 cloud caused by the fresh fuel. 



Imagine then, instead of this, the enormous fiery disc 

 of the sun, upon which from time to time, fall fragments 

 of comets and of cosmic clouds. Obviously the arrival 



