OBSERVATIONS UN TDK ZODIACAL UUHT. 



No. 338. 



MOON ZODIACAL LIGHT. 



MAY 15th, 1834. 



Lat. 40 31' N. : Lon. 142 59' E. 

 Zenith point, Lat 48 37' N. : Lon. 267. 



The eastern horizon had some haziness over it, yet not so great as to prevent the moon's disc from showing itself 

 (though dimmed) as soon as it readied the horizon. Watched attentively for an hour previous to its rising, in order 

 to catch every appearance of the sky. Thought sometimes that there was a paling of the sky up as high as Spica, 

 from &' 1 37 m on ; hut this was very uncertain. On the whole, I rather conclude that there was none. Except the 

 haziness, the evening was a very interesting one ; for the angle of the ecliptic with the horizon is so small, that the 

 moon approached very slowly, and so gave me ample time for observations, after its light first hegan decidedly to 

 show itself. The moon was also now ahout its furthest possible distance from the equator ; and this, together with 

 the small angle of the ecliptic to the horizon, gave excellent opportunities for testing whether the Light is a reflection 

 from the atmosphere piled into an equatorial ridge, or from something else. The conclusion soon became clear to 

 my mind, that the former could not be the case. (See also the chart.) 



At 10 h 8 m the sky began to show a faint blush, decidedly light from the moon. Could not get boundaries till 

 10" 20 m , when they were as in the line a; at 10' 1 23 m , they were as at b ; 10" 27, still at b, but light strengthened ; 

 10 h 28 m , as at c; and now there might, perhaps, be called a Stronger Light, with the boundaries at m ; but the 

 haziness prevented this from equaling former exhibitions of that kind. At 10 h 29, the upper edge of the moon 

 showed itself above the smooth-sea horizon ; but the haze there kept it so dim, that the boundaries c and m still 

 continued till 10" 31 ra . 



The quick rounding off of the Light on the right side, as at a; a; x, was quite striking this evening. Had it not 

 been Zodiacal Light, it would have naturally extended slantingly off on the right as well as on the left. 



