150 THE APPARENT POSITION OF THE ZODIACAL LIGHT. 



i 



themselves, which nearly coincides with the ecliptic, the number of Durchmus- 

 terung stars to the square degree is slightly greater than on other lines parallel 

 to it on each side. To complete the inquiry thus suggested, straight lines were 

 laid down on the chart between the limits of right ascension 10 h m and 12 h m , 

 with the following limits in declination: -f-6° to — 5°; -j-8° to — 3°; -j-10° to — 1°; 

 +12° to +1°; +14° to +3°; +16° to +5°; +18° to +7°. The first two of 

 these lines extend beyond the limits of the Durchmusterung. The numbers of 

 square degrees within these limits which are intersected by the lines are respec- 

 tively 26, 32, 36, 36, 36, 36, 36 ; and the corresponding mean numbers of 

 Durchmusterung stars to the square degree are 9.0, 9.7, 10.0, 9.9, 9.3, 8.5, 8.4. 

 Here again a slight maximum is indicated for the vicinity of the ecliptic. It 

 accordingly seems to be a fact, so far as it can be determined by the Durchmus- 

 terung, that there is a slight relative abundance of stars all along the ecliptic be- 

 tween the limits of right ascension 8 h m and 13 h m . This conclusion is confirmed 

 by inspection of the Durchmusterung atlas. It is not at present to be assumed 

 that the distribution of the fainter stars follows the same rule, or that the slight 

 variations of stellar density here found are sufficient to be distinguishable to the 

 eye of an observer; still, considering the faintness of the zodiacal bands occasion- 

 ally reported, their nature may perhaps be rendered a little doubtful by the 

 statistics of the distribution of Durchmusterung stars which have just been consid- 

 ered. In time to come, photography may resolve some of the difficulties now 

 attending inquiries of this kind. 



The orbits of the known asteroids naturally suggest themselves as another 

 possible source of information with regard to the distribution of light in the 

 zodiac. The discovery of so many small planets between Mars and Jupiter makes 

 it seem somewhat probable that large quantities of meteoric dust may circulate in 

 the same region, and in orbits similar to those of the separately visible objects 

 which have been found there. The appearance of this dust from a distance 

 might have a general resemblance to that which would result if the asteroids left 

 permanent traces of light behind them in their movements. But in attempting to 

 determine this effect from the orbits of the asteroids hitherto discovered, it must 

 be remembered that the circumstances under which the search for them has been 

 conducted may produce apparent peculiarities in their distribution. 



The elements of the first 237 asteroids, as given in the Berlin Jahrbuch for 

 1887, have accordingly been examined with some care, and several tabular ar- 

 rangements of these elements have been formed, to exhibit any peculiarities which 



