480 THE POPULAR SCIENCE MONTHLY. 



Our ring, incomparably smaller, covers only a narrow zone of the polar 

 regions, the center of which is at a considerable distance from the 

 pole. The inhabitants of Saturn's equator if there are any look out 

 upon a ribbon very wide in the vertical but very narrow in the hori- 

 zontal direction. On the other hand, an observer in the high latitudes 

 of Asia or America stands in the presence of a corona of little thick- 

 ness, but relatively extensive ; that is, the development of our ring is 

 nearly parallel to the part of the terrestrial surface dominated by it, 

 and which it would overshadow if it were opaque. 



To this theory the objection may be offered, that no one before 

 M. Nordenskjold has remarked the meteor in question, while many 

 should have done so if it is permanent. An observer standing near 

 the auroral pole should perceive a luminous circle completely envelop- 

 ing the horizon. M. Nordenskjold replies to this by saying that the 

 luminous arc is only a residuum of more brilliant and more complex 

 phenomena ; we can hardly hope to see it except in years when auro- 

 ras are weak, or years of minima, of which the year 1878-'79 was one. 

 Most commonly the accessory masks the principal, much in the same 

 way that we can not see the foundations of a house while the building 

 is standing. The light of the ring is so weak that not only the day 

 and the twilight, but simple moonlight makes it invisible. If the sky 

 is charged with frost, it will all disappear, and even the presence of 

 too much vapor in the air extinguishes it. The observer must, then, 

 be favored with dry and cold weather. If the temperature is above 

 the freezing-point, it is useless to look for the corona. The coasts of 

 Norway, moist with the breezes from the Gulf Stream, are badly situ- 

 ated to give views of it. Nearly all other regions where it could be 

 perceived are dismal solitudes. In the second place, a spectator situ- 

 ated near the auroral poles would see nothing, for the horizon would 

 hide the meteor from him in the same way that a Saturnian, who 

 never left the high polar regions of his planet, would not be aware of 

 the existence of his ring. Our observer, leaving the auroral pole, and 

 going toward the magnetic south, would finally distinguish in that 

 direction an arc gradually rising above the horizon. An entire circle 

 of considerable width is dominated that is the word by the corona, 

 which is then near the zenith ; but, although the meteor may be nearer 

 the ground at that point than anywhere else, it is not visible there, for 

 it is too thin to be seen, looking at it vertically. Outside of this latter 

 zone, another zone, concentric with it, enjoys the sight of the arc, now 

 situated obliquely in the direction of the magnetic north. Further 

 on, the arc, grazing the horizon, ceases to be visible ; some time be- 

 fore reaching this point, in fact, it is hidden by the mists that gather 

 in the horizon, as well as by the density of the atmosphere which the 

 visual rays have to traverse. M. Nordenskjold would not have been 

 able to see it if it had been only half as luminous. 



The meteor is relatively stationary, but is not rigorously motionless. 



