THE APPAEEXT POSITION OF THE ZODIACAL LIGHT. 151 



tliey might preseut. Upon the whole, it does not seem necessary that the de- 

 tails of these investigations should here be given at length, since it is not certain 

 that the classification employed would be serviceable to other inquirers, and since 

 the rapid discovery of new planets would soon deprive the results thus exhibited 

 of any appearance of completeness. It will perhaps be interesting, however, to 

 state the general conclusions which were obtained from the tiibles. 



Upon the comparison of elements published twenty or thirty years ago with 

 others computed for recent epochs, it appears that the orbits of asteroids do not 

 generally vary with such rapidity as to invalidate, in the course of half a century 

 at least, any statistical results like those here described. The distribution in 

 longitude of the ascending nodes of the known asteroids was the first subject of 

 inquiry, and the conclusion was obtained that the zodiacal band formed by the 

 collective orbits would have its least extension in north latitude about the longi- 

 tude 0', and its least extension in south latitude about the longitude 180°. The 

 coincidence of this result with that already found for the zodiacal light induced 

 me to try the effect of a stereographic projection of the northern halves of the 

 orbits on the plane of the ecliptic. In tliis projection, the nodes and inclinations 

 of the orbits were the only elements emploj^ed, so that the supposed band was 

 regarded as seen from the Sun. The radius of the projection was five inches. 

 Upon this scale a distinct band of shading was formed by the lines representing 

 the orbits of the first 120 asteroids; the remaining 117 were laid down upon a 

 separate chart. Both charts, but especially the first, exhibited a depression of the 

 edge of the band in the region near the longitude 0°, as had been expected. The 

 same charts will also represent the southern halves of the orbits if we regard all 

 the longitudes as increased by 180'. 



Farther examination showed that the asteroids to which this peculiarity is 

 due are those having their perihelia in south latitude. The general result thus 

 obtained may be sufficiently well exhibited by stating the number of ascending 

 nodes for each quadrant of longitude, beginning at 40', which occur in the orbits 

 of asteroids having their perihelia respectively in north and in. south latitude. 



LongitTides of ascending nodes. 



Perihelia in north Latitude . . 

 Perihelia in south latitude . 



Total 55 78 29 75 



The band formed by the collective orbits with perihelia in north latitude, ac- 

 cordingly, would not have any distinct tendency towards north and south latitude 



