ASTRONOMY AND METEOROLOGY. 365 



their nodes, and change the positions of their planes, which after 

 some oscillations, will rest in the direction of the sun's motion. The 

 perihelia of all the small and rare bodies belonging to our system, 

 and the intersection of their orbits, must be, therefore, situated 

 between the sun and the point to which he moves, and the line or 

 the narrow space extending in this direction, will be accordingly 

 crowded with swarms of them, arriving there from every quarter of 

 the planetary regions. From the great extent of surface which they 

 possess, even with an inconsiderable amount of matter, they are 

 enabled to reflect a large portion of the solar rays, and to this cause 

 we may justly ascribe the ZODIACAL LIGHT. In the opposite 

 part of the heavens, a like, though less dense collection of these cos- 

 mical particles, cluster in order to pass their common aphelion ; and, 

 though at too great a distance from the sun and from the earth to 

 send any sensible portion of light to northern latitudes, they some- 

 times cause the appearance which Humboldt, (describing the Zodiacal 

 light in tropical climates after sunset,) calls " a faint reflection visible 

 in the east." 



As the sun's rays are very intense and powerful in his vicinity, 

 they must be reflected by a more extensive zone of these numerous 

 bodies, and hence proceeds the conical form of the zodiacal light, its 

 greater intensity at the base, and its gradual evanescence at great 

 distances from the sun. The extraordinary length and brightness of 

 the cone during some years, the diminution and the disappearance of 

 it at other times, are owing to very great irregularities in the supplies 

 of materials by which it is reflected ; while the flickering and waver- 

 ing of the light are caused by the frequent interception of the rays, 

 as the small bodies change their relative positions. During the month 

 of June, this cone of light (which always retains the same actual, 

 though not the same apparent position,) is at its nearest distance 

 from the earth ; but in this and the other months of summer, it con- 

 tinues above the horizon only during the day, and is therefore invisi- 

 ble. I am inclined to think, that repeated observations of the position 

 of the cone of light should enable us to ascertain with great accuracy, 

 the direction in which our system is travelling through space, or may 

 perhaps serve to detect some motion in our universe. 



The uniform position of the orbits of all these small and rare 

 bodies, might be expected to present favorable conditions for the 

 play of their feeble attractions, especially at their greatest distances 

 from the sun ; and if we suppose a union to occur, whenever they 

 cluster there in unusually large numbers, we may find a very plausi- 

 ble explanation for the ORIGIX OF COMETS. Nor should a comet 

 thus formed, have the axis of its orbit fixed in the direction of the 

 solar motion. As the mass enlarges, the disturbances of the planets 

 will preponderate over the resistance of the medium, and cause a 

 motion of the line of apsides. By this means the increase of size 

 will be arrested, and in the space from which it has removed, a new 

 accumulation may be expected to commence, as soon as the collisions 

 of cosmical masses, and the entrance of fresh acquisitions of matter 



