534 OBSERVATIONS ON TUB ZODIACAL LIGHT. 



No. 267. 



DECEMBER 25th, 1854 : EVENING. 



Lat. at 7/i. , 16= 31' N. : Lon. 101 25' W. 



Sun set at 5k. 30m. 



Joint BUQ and muim at 6A. 30m. : Stronger Light at miduight. 

 Suu's Ion. 273 2(i'. 



Joint Sun and Moon Zodiacal Light, &c. I have been on the watch, ever since my observation of March 6th, for a 

 joint sun and moon Zodiacal Light, but have not been successful until this evening, when the moon being in the right 

 position, and the sky remarkably clear and bright clear down to the very horizon I had a successful and a remark- 

 ably interesting observation. Going on deck as soon as the evening had sufficiently advanced i. e., at 6 h 50 1 " I 

 found the sky decidedly marked by a bright streak within the usual bounds of the Zodiacal Light. This had not 

 the ordinary warm coloring of the Zodiacal Light ; but was more like a dim silvery moonlight ; but of the greater 

 brightness itself, within these boundaries, there could be no doubt. I sent for Dr. - , and asked him to tell me 

 whether he saw any particular brightness in that part of the sky ; which he did at once, giving it the boundaries 



that I have given in the chart, except that he did not carry it so far up. Captain Lee and acting Lieutenant K , 



then on the poop-deck, also made it out without any difficulty. This observation is the more interesting and 

 remarkable from the fact that the Light, although deriving its strength, in a great degree, from the moon (to such 

 a degree as to make it surpass the surrounding moonlight itself), did not stretch up exactly in the direction of the 

 moon, but kept within the Zodiacal Light bounds, while the moon itself was quite outside of these. See the position 

 of the moon in the chart. This Light continued till *7 h 48 m as striking as at the first sight of it at 6" 50 m . At 8" 

 it was not so strongly marked ; at that hour, however, it appeared to stretch up beyond the moon ; but of this last 

 I am not certain. 



The night being so fine for observations, I determined to have observations of the simultaneous east and west 

 Zodiacal Light as early and as late as it would exhibit itself; to be made with particular care. The moon, 

 however, did not set till ll h 36'", and its effulgence in the western sky continued for some time after. Immediately 

 on its setting, the eastern Zodiacal Light became manifest, quite decidedly showing itself; but its right-hand or 

 southern boundary was so uncertain, that I cannot give the one in the chart as fully reliable. The western Zodiacal 

 Light, when the moonlight was fully gone, showed itself also, I thought decidedly, and I got its boundaries without 

 difficulty. But neither in the east nor west was this Zodiacal Light so satisfactory or strong as on previous recent 

 occasions. The horizon, at midnight, has now changed considerably, owing to our rapid progress to the south, and 

 the ecliptic and it are no longer perpendicular, as before. 



At 1 o'clock, in the west, there was nothing reliable. In the east, the Light had strengthened ; but I had the 

 same difficulties about its boundaries as before. 



(The direction of this Light, at the observation of 7 h 50 m , may show that the moon exercised no sensible attrac- 

 tion in the substance producing it.) 



P. S. December "26, Evening. I looked this evening to see whether there might be a similar Zodiacal Light ; but there 

 was none. The moon had doubtless got beyond the proper position for such a result. 



