

H. Skey. — On the Zodiacal Light. lol 



light subtended an arc of 40° from the base to the vertex. Tt was also seen 

 on the 5th after twilight and on the 26th, at 7.30, it subtended an arc of 45°. 



August 1st — It was very clearly visible at 8 p.m., subtending an arc of 

 nearly 60°; also on the 26th, when the air was so transparent that small 

 stars could be seen very near to the horizon. The length of arc being 

 about 45°. 



September 1st — It was also observed. The angle subtended is less, but 

 the vertex now reaches nearly to the Milky Way ; also on the 19th and very 

 distinctly on the 27th, its vertex now reaches the Milky AVay in the constel- 

 lation Scorjno. 



October 2nd, 4th, 5th, and 21st, the same light was visible for a short 

 time after sunset, but its vertex soon sets at this season and ceases to be 

 seen in the evenings. This light was never seen in the mornings before 

 twilight and sunrise in any of the preceding months, although looked for 

 under favourable circumstances, but it begins to be faintly seen in the 

 mornings in the beginning of March, and on the 31st it was very distinct 

 extending along the ecliptic, subtending an arc of 30° at 3 a.m., and of 45 

 at 4 a.m., reaching nearly to the Milky Way and pointing to Antares. 

 During April and May it is still seen, but in June it becomes so faint as 

 to be doubtful. It began to be faintly seen, however, in the western sky at 

 the end of June in the ecliptic pointing and extending near to Sjnca Virginis 

 and was seen every favourable evening in July reaching to Spica Virginis. 

 In August it extended beyond that star reacliing nearly to Antares, subtending 

 on the 23rd an arc of 50° at 8.30 p.m. In September it had the same 

 appearance as in 1872, extending to Antares. 



During the years 1873 and 1874 it also presented the same appearance at 

 those times. 



A summary of these observations shows that in S. Lat. 46° this illumina- 

 tion begins to be visible in the evenings after twilight, and when the moon is 

 absent at the end of June ; early in August it attains its greatest elongation 

 and brightness, forming quite a feature in celestial scenery ; it then gradually 

 decreases till the end of October, when it ceases to appear in the evenings, but 

 can be seen in the mornings in March, April, and May, and very faintlv in 

 June. Its inclination to the plane of the ecliptic appears to be nearly four 

 degrees, the advancing cone seen in this latitude lying on the south side of the 

 ecliptic. 



It always points towards the same constellation, Scorpio, whether seen in 

 mornings or evenings, showing that it is that part only of the zodiacal 

 envelope which is on one side of the solar orb which can be seen in this lati- 

 tude, and that that part is in advance of the solar motion in space. 



The colour of the illumination as seen in south latitude is invariablv clear 



