

G. Jones on the Zodiacal Light. 385 



observations of the Luminous Arctj was able to trace out, bettej,- 

 its dimmer markings on the sky. We may perhaps estimate, 

 witli safety, the width of the Limiinous Arch as decidedly given 

 to the eye, 30^ : but doubtless the nebulous matter of this ring 

 extends beyond that ; of which we have proofs in the much 

 greater width of the Zodiacal Light near the horizons, where 

 the sun, bringing the very diifuse matter at the edges into vision, 

 Fhows us what the eye in other parts of the arch was not able 

 to detect 



As respects the singular offset, or sudden change of brightness 

 repeatedly noticed witliin the outer boundaries, as if there might 

 be two rings, the one nearer to us and of greater brightness than 

 the other, I will not venture an opinion, with the slight data now 

 in my possession. The offset was not always perceived; but, 

 when seen, Avas of so decided a character as scarcely to leave any 

 doubt of its reality. This inner ring, as I will call it for sake of 

 distinction, had an average width of 14^ 5-i'. 



The very dim light frequently seen beyond the usual bound- 

 ary on the south when I was at my furthest removes from the 

 ecliptic in that direction, seems also scarcely to admit of a solu- 

 tion, with our present knowledge of the subject. This dim, 

 lateral light has, on my charts, a remarkable uniformity of 

 breadth; never less than twenty-three or greater than twenty- 

 seven degrees. The reader will remark that I saw it only on 

 the southern side of the Luminous Arch. 



6. Tlie amount of matter in this nebulous ring must be pro- 

 digiously great. Estimating its width at SO'^ and its distance 

 from us at 100,000 miles, its width would be 52,600 miles: its 

 thickness must, at present, be a subject only of conjecture: but 

 at any thickness which dynamics will admit of, the amount of 

 material there must be immensely great. It will be remembered 

 that the width, 30^, is only that of the Luminous Arch as pre- 

 sented to the eye : beyond its borders, there seems still to extend 

 nebulous matter too diffuse to be seen except by the power of 

 the sun. 



, 7. The last sentence above would indicate that I consider 

 this nehulotts matter as self-luminous^ as well as capable of giving re- 

 J^cted light:— to which opinion I am very strongly inclined. 1 

 had observations of other phenomena tending to confirm this 

 <^pimon: but to notice them would lead me quite beyond my 

 present limits, and into another subject. 



I 8. The opinion which I advanced at the meeting of the Sci- 

 entific Association in Providence two years ago, — that this ring 

 "^^y be the source of our aerolites^ seems to have much to support 

 it: but there is not room to discuss it here. 



Brooklyn, N. Y., Sept. 11th, 185t. 



SECOND SERIES, VOL. XXIV, NO. 72. NOV., 1857, 



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