658 OBSERVATIONS ON THE ZODIACAL LIGHT. 



No. 329. 



MOON ZODIACAL LIGHT. 

 OCTOBER 21st, 1853. 



Lat. 22 11' N. : Lnn. 1 13 35' E. 

 Sun set at 5^. 28m. 



I 8h. 12m. 



Observations recorded at< 8 15 

 ^8 17 



This evening, as the time approached for the moon's rising, I turned to see whether there might be a lunar 

 Zodiacal Light. I have often made this attempt during the cruise (see especially March 29th, 1853*), but, until 

 this evening, never could succeed to my satisfaction probably in consequence of my looking too far up, and expecting 

 this light too much to resemble the sun's Zodiacal Light. Last evening, at 7'' SO" 1 , while finishing my observations 

 in the west, the quartermaster on duty said to me, " The moon is going to rise." I went over soon after to look at 

 the sky, and was struck at once with some resemblance to the sun's Zodiacal Light, but was too uncertain to do more 

 than to watch it carefully. There was also scarcely time to get my star-charts and to make annotations. By-and-by, 

 however, the sudden lateral spread of light (exactly like that in the morning, when the Zodiacal Light changes to 

 that of dawn or atmospheric light) was so striking as greatly to remove my doubts. It was then, however, too late 

 for taking outlines. So I was prepared this evening. At I 7" 56 m , a faint and rather doubtful light began to appear 

 from the Pleiades down, about the line of the ecliptic. At 8 h 2, it was of a pretty decided character. I now sent for 



Lieut. M , to request him to assist rue with his judgment. At 8 h 10'", when he got on deck, there could be no doubt. 



He saw the light at once. It was exactly in the bounds of the sun's Zodiacal Light, with the shape this latter assumes. 

 It extended rapidly, still, however, keeping within the Zodiacal Light bounds. Its boundaries, at 8" 12 m , 8' 1 15"', 

 and S' 1 IT'", are given in the chart. It kept these last bounds till 8" 22'", when it suddenly broke limits, and spread 

 laterally so fast, that, in two minutes, no definite boundaries remained. The resemblance to the first breaking of 



morning dawn was very striking. Lieut. M agreed with me in all the above remarks, except the resemblance 



to the morning light breaking bounds suddenly, which last he has not observed. 



* The record in my MS. for March 29th, 1853, was as follows : 



"I have been trying to see whether there is any Zodiacal Light by the moon, which is now in a fnvorable condition for ir, if there is any, and have, at times, 

 thought that there is such light; but I cannot get hold of any thing reliable. There is n i doubt, however, that, when the moon rises now, its light, cone- 

 shaped or triangular, is first shown at the bottom of the Zodiacal Light place. It was so, very decidedly, ou the 27th instant, when the moon was nearly at 

 full, and the horizon was clear. This evening the horizon was obscured by cirri; but. at 'Mi. .">!lm., 1 had an observation of a light on the ecliptic, parabolic in 

 shape, 5'2 in width, and ascending to 25 above the horizon. At !)A. 56m. it extended (>^ un the horizon, and rose to a height of 32. Then it ascended 

 quickly to a height of 35 from the horizon, where it remained till the sky was all brightened rapidly by the approaching moon, which rose at ten minutes 

 past 10 o'clock. " (The Lat. then was about 2 N. : Lou. about 104 21' E.) 



