382 



V 



G. Jones on the Zodiacal Light. 



removed from the equator. At Quito I liad the portion CI as 

 represented here, from causes hereafter explained; above I the- 

 Arch had a uniform width across to the horizon at A. As the 

 night wore round and the western horizons changed to F, D, H, 

 and finally to J, &c. — the opposite end of the Luminous Arch 

 would change from A, to h^ c, rf, e, and finally to/: so that during 

 the night the whole circle would be seen, except B/ which if the 

 diagram here were entirely symmetrical^ would be seen to be 

 equal to 40°. The dotted lines S, S', S", &c., represent the sun's 

 rays, and the angles S'BO, S"FO, S^"DO, &c., will be the angles 

 between the incident and reflected rays, the spectator being at 0. 

 The following table will represent the value of these angles, and 

 will show, according to Bouguer's tables, the number of rays 

 reflected to the eye out of every thousand incident rays. 



Angks- 



-degrees. 



Rays re 

 smoo 



S'BO. 





161 



1 



S"FO, 





146 





S"'DO, 





131 





S""HO, 





116 





S'"" at midnight, 90 





S'""otO, 





67 



; 

 \ 



843 



184 



101 



59 



28 



18 



Raya refiectcd from plate 

 glass not quicksilvered. 



The harmony between either of these columns of reflected 

 rays, and tlie intensity of the Zodiacal Light from the horizon 

 upward, is very remarkable- We do not know fully what nebu- 



lous matter is ; but we may reasonably conclude that the laws 



for reflection of light, which Bouguer has discovered to apply to 



all other substances, apply also in this. 



In my late observations, this Light was always brightest at the 

 horizon and always brighter the nearer my horizon w^as to the 



sun : I studied it, night after night, with reference to these^ laws 

 of reflected light, and constantly with an increasing conviction 

 that a geocentric ring is the only one that could admit the phe- 

 nomena presented to my eyes. 



^ 3, The position oj this ring as regards the ecliptic. In deciding^ 

 upon this point, I shall be governed by the central line, or line ot 

 strongest light; and this was usually pretty well marked on the 

 sky; so decidedly marked that the three gentlemen whom I have 

 already spoken of as having been suddenly added as observers, 

 had no hesitation in immediately stating its position among the 

 stars, although they had never before noticed this Lununous 

 Arch; and bad now received no further aid from me, than to 

 direct their attention to it, and to ask them to observe that the 

 central part was the brightest portion of all Since the whole ot 

 this arch followed slightly in my direction, as I was carried m a 



Single night by the axial motion of the earth to the nortU 



It is not so, the earth being disproportionately large. 



:*»- %. 



