.CERTAIN HARMONIES OF THE SOLAR SYSTEM. 55 



material giving the zodiacal light by older hypotheses (which he does not claim) ; 

 nor yet that of a ring like those of Saturn; nor yet a ring of greater thickness, 

 partially luminous indeed in appearance, as Mr. Jones would have it; but we must 

 have for it the form of what may rather be termed a girdle, of no great thickness, 

 it may be — it is too translucent for that — but yet of very considerable width, such 

 as will provide for the broad base of tlie Zodiacal Light, and the extended elliptical 

 spot which exhibits the ^' gegensehein'"^ opposite to the sun; and which latter would 

 seem to be almost wholly due to reflection. There may also be some reason to 

 suppose that the curvature of the girdle, on the one side at least (that on which 

 the "gegenschein" appears) is such as would be due to a spheroidal shell such as 

 has been described in Article (37) of this paper. Such a girdle, withal, could not 

 always — perhaps ever — have all its breadth enveloped in the eartKs shadow. 



Hoio the Girdle is maintained. 



(79) The question at once becomes a pertinent one. How can such a girdle 

 escape destruction by the continued perturbation of the moon, acting in close 

 proximity ] 



The answer to this question may be found, if the girdle be so situated that its 



TIME OF REVOLUTION AROUND THE EARTH SHALL BE EQUAL TO, AND IN THE SAME DIREC- 

 TION "WITH, THAT OF THE MOON. The Conditions requisite to fulfil this will first be 

 considered, and then the phenomena that seem to be accordant with the actual 

 maintenance of such conditions. 



(80) If the earths attraction cdone were concerned, the form of the revolving 

 girdle must, it Avould seem, be that of a spheroidal shell; such as that indicated 

 in (37). The attraction of the moon will distort this, yet so that the shape shall 

 also be consistent with the stringent condition as to the periodic time. 



Fiff. 13. Ficr. 14. 



/ 

 f 



I 



f 



A 





' Counter-gleam, we might perhaps term it ; though that scarcely seems so apt as the German word 

 for the same thing, here quoted. 



