Sun Viewing and Drawing. 445 



reproduced by some such alternate process of refrigeration, 

 breaking-up, and subsidence ; and that it is from this more 

 solid matter that the solar radiation of light and heat mainly 

 proceeds. " An incandescent liquid or gas," as the President 

 of the Royal Astronomical Society, too, observes, " such as 

 we suppose the sun's atmosphere to consist of, will not give 

 out light. We want, therefore, something floating in it, or 

 where could the light come from ?" 



While on this subject of crystallization and subsidence, the 

 writer would here state how, on more than one occasion, he 

 has been reminded of such a state of things by a curious and 

 interesting (if not very analogous) phenomenon presented to 

 view in the boiling salt-pans at Droitwich in Worcestershire. 

 The crystals of salt, varying much in form and size according 

 to the temperature of the liquor out of which they are pro- 

 duced, first form on the surface of the hot brine, and then, 

 after a while, begin to subside in patches not very unlike solar 

 spots, or groups of spots. Other portions of the yet floating 

 crust of salt may frequently be seen marked with bright 

 blotches and reticulations, more nearly resembling solar facuke, 

 so far as mere form is concerned, than any other object he 

 could readily call to mind. It is not, however, here intended 

 that we are to consider the sun as a merely vast mineral salt 

 bath ) though sodium, at any rate, appears to be present there 

 in sufficient abundance ; and the mean density of his mass is 

 just about the same as that of the brine ! 



A curious theory of the origin of solar spots, at present 

 in increasing favour with some of our most philosophical 

 observers* is, that they are produced b}^ external planetary 

 influences. Every twenty months or so, as they observe, the 

 spots seem to assume the same sort of behaviour in their 

 manner of forming and disappearing. With this circumstance 

 is to be coupled the fact that every twenty months the planet 

 Venus returns to the same position with reference to the earth, 

 and that then, too, we see that, as any portion of the sun's 

 surface retreats from the neighbourhood of Venus, the solar 

 spots on that portion have a tendency to increase, attaining a 

 maximum at the point furthest from Venus. And the inference 

 they draw from this curious phenomenon — backed up by certain 

 physical experiments in connection with heat, light, electricity, 

 vaporization, pressure, etc., is that the sun is probably in such 

 a sensitive molecular condition that its mass may experience 

 wonderful changes from very small outward influences. 



Now that the continuity of the outermost strata of the sun 

 is, from some cause or other, subject to the most astonishingly 

 extensive, and often rapid changes, is certain enough ; as may 

 * Messrs. De La Rue, Balfour Stewart, Loewy, and others. 



