A.EBOLITES. tI5 



during an Aurora Borealis, certain portions of the vault of 

 heaven, which were not illuminated, light up and continue 

 luminous whenever a shooting star passed over them. 



The different meteoric streams, each of which is composed 

 of myriads of small cosmical bodies, probably intersect our 

 Earth's orbit in the same manner as Biela's comet. Accord- 

 ing to this hypothesis, we may represent to ourselves these 

 asteroid-meteors as composing a closed ring or zone, within 

 which they all pursue one common orbit. The smaller 

 planets between Mars and Jupiter, present us, if we except 

 Pallas, with an analogous relation in their constantly inter- 

 secting orbits. As yet, however, we have no certain know- 

 ledge as to whether changes in the periods at which the 

 stream becomes visible, or the retardations of the phenomena 

 of which I have already spoken, indicate a regular precession 

 or oscillation of the nodes that is to say, of the points of 

 intersection of the Earth's orbi.t and of that of the ring ; or 

 whether this ring or zone 9 e'cains so considerable a degree of 

 breadth from the irregular grouping and distances apart of 

 the small bodies-, tnat it requires several days for the Earth 

 to traverse it. The system of Saturn's satellites shows us 

 likewise a group of immense width composed of most inti^ 

 mately-connected cosmical bodies. In this system, the orbit 

 of the outermost (the seventh) satellite has such a vast di- 

 ameter, that the Earth^ in her revolution round the Sun, 

 requires three days to traverse an extent of space equal to 

 this diameter. If, therefore, in one of these rings, which 

 we regard as the orbit of a periodical stream, the asteroids 

 should be so irregularly distributed as to consist of but few 

 groups sufficiently dense to give rise to these phenomena, we 

 may easily understand why we so seldom witness such glorious 

 Spectacles as those exhibited in the November months of 

 1799 and 1833. The acute mind of Olbers led him almost to 

 predict that the next appearance of the phenomenon of shoot- 

 ing stars and fire balls intermixed, falling like flakes of snow, 

 would not recur until between the 12th and 14th of November, 

 1867. 



The stream of the November asteroids has occasionally 

 only been visible in a small section of the Earth. Thus, for 

 instance, a very splendid mo' a oric shower was seen in England 

 in the year 1837, whilst a mob v attentive and skilful observer 



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