ASTRONOMY AND METEOROLOGY. 397 



was simply an optical spectrum a deep blue fringe to the light haze 

 caused by the object-glass of his telescope having been accidentally over-cor- 

 rected for one of the irregularities incident to chromatic refraction. This no- 

 tion, of course, became altogether untenable so soon as it was known that 

 the same appearance had been noted by other telescopes, in which the same 

 incidental imperfection had no place. All felt that the shadow could not bo 

 referred to a regular atmospheric investment of the moon's solid sphere, be- 

 cause under such circumstances the streak should have been ahvavs seen, 



f 



when the rim of the moon rested in a similar way across a planetary disc. 



* w 



The sagacious Plumian professor of astronomy at Cambridge, Professor 

 Challis, seems to have been the first to hit upon the true interpretation of the 

 riddle. The indefatigable star-seer has long suspected that the broad dark 

 patches of the lunar surface the seas of the old selenographists are really 

 shallow basins filled by a sediment of vapor which has settled down into 

 those depressions ; in other words, he conceived that there are fog-seas, al- 

 though there are no water-seas, in the moon. The general surface and 

 higher projections of the lunar spheroid are altogether uncovered and bare ; 

 but vapors and mists have rolled down into the lower regions in sufficient 

 quantity to fill up the basin-like hollows, exactly as water has gravitated into 

 the beds of the terrestrial oceans. The professor, using the high powers of 

 the magnificent telescope furnished to the Cambridge Observatory by the 

 munificence of the late Duke of Northumberland, was able to satisfy him- 

 self that the planet actually did come out from behind a widely gaping hol- 

 low of the moon's surface at the bottom of a lunar fog-sea, seen edgewise, 

 so to speak. If a shallow basin extended for some distance round the curv- 

 ature of the lunar spheroid, and if it were filled up with vapor, that vapor 

 would rest at a fixed level, exactly after the manner of a collection of liquid, 

 and such fixed level would be concentric with the general spheroidal curva- 

 ture of the satellite. Under such an arrangement, there would therefore 

 necessarily be a bulging protuberance of the vapor-surface, through which a 

 remote luminary might be seen, when it rested in the requisite position. 

 This, then, is Professor Challis's understanding of Jupiter's hint. The moon 

 has fog-seas upon her surface, and the band of shadow visible upon the face 

 of Jupiter as the planet came out from behind the earth's satellite, was a thin 

 upper slice of one of those fog-seas seen by the favorable accident of the 

 planet's light shining for the instant from beyond. 



SPOTS OX THE SURFACE OF THE SUN. 



The Royal Astronomical Society, G. B., have recently presented their 

 medal to Mr. Heinrich Schwabc, of Dessau, Germany, for his researches, 

 continued for a period of thirty years, on the spots which appear on the sur- 

 face of the sun. From the address of the President, in presenting the 

 medal, we derived the following information on this topic. 



The plan adopted by Mr. Schwabe is, to note by a number each spot in 

 the order of its appearance, carrying on his notation from the first to the last 

 spot in each year. He reckons an. isolated spot, or a cluster of spots where 



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