54 STATEMENT AND EXPOSITION OF 



catch this reflection from only one portion of it; and. the rest is dull to our vision. 

 If we could with great rapidity change our positions, other portions of the silvered 

 edge would show themselves according to our changes of place. So also, when a 

 rainbow is presented to our eye; the myriads of drops of falling water in the whole 

 rain-shower are sending off from each drop reflections of light in all directions, and 

 the universal atmosphere about us is full of these brilliant variously-colored rays; 

 but only that portion, which, to us, forms the rainbow arch, can reach our eye ; and 

 all the rest is lost to our sight." 



" So it is also with the Zodiacal Light ; and the proof that we never see the whole 

 of its extent at once, is manifest in the following facts : — 



" 1. When I was in a position north of the ecliptic, the main body of the Zodi- 

 acal Light was on the northern side of that line. 



" 2. When I was south of the ecliptic, the main body of the Zodiacal Light was 

 on its southern side. 



" 3. When my position was near or on the ecliptic, this Light was equally divided 

 by the ecliptic, or nearly so. 



"4. When, by the earth's rotation on its axis, I Avas, during the night, carried 

 rapidly to or from the ecliptic, the change of the apex, and of the direction of the 

 boundary lines, was equally great, and corresponded to my change of place. 



"5. That, as the ecliptic changed its position as respects the horizon, the entire 

 shape of the Zodiacal Light became changed, which would result from new portions 

 of the nebulous matter coming into position for giving us visible reflection; while 

 portions lately visible were no longer giving us such reflection."-' 



(76) The phenomena here commented upon all serve to confirm the assertion, 

 (75), that the zodiacal illumination must largely be transmitted light; and so the 

 illuminated material appear brighter in the special direction in lohich the light is 

 transmitted ; as the sun illuminates the partially transparent vapor in our atmos- 

 phere through rifts in the clouds, and thus produces the appearance familiarly 

 described as "the sun drawing water. "^ 



(77) The light being .transmitted, other phenomena would also be in place, 

 among which are absorption — possibly interference— nwdi also fluorescence; new 

 waves being originated in this case, as well as, perhaps, in that of the comets ; 

 the spectrum-analysis of whose light seems to show, among other phenomena, 

 characteristics of self-luminous material. 



(78) To this it may now be added, that the nebulous ring of Chaplain Jones, 

 may well be regarded as having, indeed, not the lenticular form attributed to the 



' "The first four of these results were not always uniform ; but the exceptions were few, and were 

 probably occasioned by the nebulous ring's not lying exactly in the plane of the ecliptic." From the 

 Introduction to Chaplain Jones's Report, pp. xvi iind xvii. 



^ Mr. Proctor also seems inclined to admit the possibility of a more intense illumination in special 

 directions ; though not decided as to its cause, when he says at the close of his Note on the Zodia- 

 cal Light, referred to in (T3) : "If some solar action, for example, rouses luminosity in certain defi- 

 nite directions—as, for instance, near the plane of the Sun's equator—in some such way as light is 

 caused to appear along radial lines through and beyond the heads of comets, our power of theoriz- 

 ing from such considerations as have been dealt with in this paper would be limited." 



