294 THE POPULAR SCIENCE MONTHLY. 



fectly inexplicable (as it seems to us) if the sun occasions all these me- 

 teorological changes in Jupiter, as he occasions all the changes which 

 take place in our earth's atmosphere. The alternation of day and night, 

 which is one of the most potent of all the circumstances affecting the 

 earth's meteorological condition, appears to have no effect whatever on 

 the condition of Jupiter's atmosphere ! 



Now, as respects the alternation of summer and winter, we can 

 form no satisfactory opinion in Jupiter's case, because he has no seasons 

 worth mentioning. For instance, in latitudes on Jupiter correspond- 

 ing to our own, the difference between extreme winter and extreme 

 summer corresponds to the difference between the warmth on March 

 12th and March 28th, or between the warmth on September 15th and on 

 September 30th. Yet we are not without evidence as to seasonal me- 

 teorological effects in the case of the sun's outer family of planets.. 

 Saturn, a belted planet like Jupiter, and in all other respects resembling 

 him, so far as a telescopic study can be trusted, has seasons even more 

 markedly contrasted than those on our own earth. We see now one 

 pole now another bowed toward us, and his equatorial zone is curved 

 now downward now upward, so as to form two half ovals (at these op- 

 posite seasons), which, taken together, would make an ellipse about 

 half as broad as it is long. As no less than fourteen years and a half 

 separate the Saturnian summer and winter, we might fairly expect that - 

 the sun's action would have time to exert itself. In particular, we 

 might fairly expect the great equatorial zone to be displaced ; for our 

 terrestrial zone of calms or " doldrums " travels north and south of the 

 equator as the sun shifts northward and southward of the celestial 

 equator, accomplishing in this way a range of no less than three thou- 

 sand miles. But the Saturnian equatorial zone is not displaced at all 

 during the long Saturnian year. It remains always persistently equa- 

 torial ! Nothing could be more easy than the detection of its change 

 of place if it followed the sun ; yet no observer has ever suspected the 

 slightest degree of systematic change corresponding with the changes 

 of the Saturnian seasons. Or, rather, it is absolutely certain that no 

 such change takes place. 



It appears, then, that night and day, and summer and winter, are 

 alike without influence on the Jovian and Saturnian cloud-zones. Can 

 it reasonably be questioned that, this being the case, we must look for 

 the origin of the cloud-zones in these planets themselves, and not in the 

 solar orb, whose action must needs be largely influenced by the alter- 

 nation of night and day and of the seasons ? 



But further, we find that a circumstance which had seemed perplex- 

 ing, w T hen we compared the Jovian belts with terrestrial trade-wind 

 zones, finds an explanation at once when we regard the belts as due to 

 some form of action exerted by the planet itself. For, let us suppose 

 that streams of vapor are poured upward to vast heights and with 

 great velocity from the true surface of the planet. Then such streams, 



