CERTAIN HARMOiXIES OF THE SOLAR SYSTEM. 59 



being readily adjustable) as the moon passes from perigee to apogee ; and they 

 will contract as the moon passes from apogee to perigee ; the cohesive power and the 

 gravitation of outer to inner portions being, in any event, insensible ; and so each 

 particle or molecule moving in its independent, or nearly independent, ellipse very 

 much as Sir J. Herschel has intimated that the molecules of comets might move.^ 



Then, too, a permanent tide must influence and control the form of the girdle ; 

 this tide (with the arrangement as in Fig. 14) being in some sense SMjjra-lunar, 

 instead of swft-lunar, in the region of the crest of the girdle extending beyond the 

 moon. 



By such a tidal action an accumulation of material will be determined toward 

 the tiDO extremities of that axis of the girdle, which at any time passes through the 

 two centres — that of the earth and that of the moon — and which is extended to 

 the girdle on both sides [i. e. toward A and B in either of the cases represented, 

 the one in Fig. 13, and the other in Fig. 14]. 



And the portions of the adjustable material here specified having themselves 

 been once so adjusted (radii-vectores and all) as to be held, or very nearly held, in 

 a dynamical equilibrium, such as is specified in (81) ; the compulsory power of the 

 forces acting on such material, under such stringent circumstances, might well be 

 supposed to bring about the form required to secure a dynamical equilibrium of 

 the girdle ; though the oscillations, in various directions, antecedent to that, would 

 present a problem of no ordinary difficulty. 



However all that may be — the dynamical equilibrium of all parts of the girdle 

 being once established, the state of things afterward would be eminently conserva- 

 tive of the same ; such being especially the case with respect to the various actions, 

 which, under other conditions, might be eminently destructive. 



(84) If the girdle (as at A in Fig. 13) were between the moon and the earth, its 

 curvature would be diminished in the direction perpendicular to the moon's orbit, 

 by the moon's own action ; though the curvature would be increased by the action 

 of the moon, on the opposite side ; as was, indeed, intimated, though not at all 

 explained, in (78). But if the girdle (as at A in Fig. 14) were outside of the moon, 

 the curvature (perpendicular to the moon's orbit) would be greater still. 



(85) The second thing proposed in this connexion, Avas to consider the pheno- 

 mena which seem to be accordant with the state of things thus far represented as 

 being merely supposable. With respect to these phenomena, it may be observed, 

 that the hypothesis of the girdle having the same periodic time with the moon 

 suggested itself as a necessity, to insure the preservation of the girdle itself; and, 

 in the brief interval which has since elapsed, the variations of the Zodiacal Light 

 have, to some extent, been carefully noted, and the7i referred for explanation to the 

 hypothesis. 



And here the phenomena seem to be more consistent with the arrangement of 

 the girdle as represented in Fig. 14 ; the point A being situated beyond the moon. 



' Cabinet Cyclopiedia— ^si!ror?o???2/(488).— With this Prof. Wright's conclusions, (IS), with respect 

 to the constitution of the material in question would not be inconsistent. See, again, Article (13). 



