THE APPARENT POSITION OF THE ZODIACAL LIGHT. 



139 



The diiferences of absorption corresponding to the evening observations of the 

 " Stronger Light " at the elongation 60' were likewise computed from the material 

 collected in the previous communication above mentioned. Tbe longitude of the 

 point to Avhich each observation relates was found from the longitude of the Sun. 

 The latitude of the axis, that is, the mean of the two latitudes given for the 

 boundaries of the light, was also computed for each observation. 



The evening and the morning observations were then separately arranged in 

 groups, each covering ten degrees of longitude. When the observations forming 

 one of these groups had all been made under similar circumstances, and pre- 

 sented a general resemblance to each other, it was practicable to employ their 

 mean results in the subsequent discussion. But in other cases, parts of adjacent 

 groups were combined to form new groups ; no group, however, was made to 

 include more than thirty degrees of longitude. The mean results for all the 

 groups are given in Table 11. Those derived from the morning observations are 

 placed by themselves after the others, as is shown in the first column. The 



