Permanent Contraction of the Planetary Orbits. 105 



The permanent contraction of the planetary orbits 

 brings us again into contact with the question of the final 

 dissolution of the visible universe, which has exercised the 

 greatest minds from the very dawn of philosophy. Mathe- 

 maticians of the last century endeavoured to establish the 

 dogma of the invariability of the mean distances and the 

 absolute stability of the planetary system. Nevertheless, 

 the conviction still remains that the present order of the 

 universe is not eternal, and the evidence afforded by Bode's 

 law of a permanent contraction of the planetary orbits 

 indicates that the dissolution of the solar system will be 

 brought about by causes now operating within the system 

 itself, although at a rate so slow as to be imperceptible in 

 the past records of astronomical observation. 



From the fact that there has been so little change in 

 the multiple proportions of the orbits of Jupiter and the 

 Earth from the period of their resolution into spherical 

 bodies, the time of the final transformation of the solar 

 system into its primordial elements appears so extremely 

 remote, that all previsions with regard to it, belong rather 

 to the poetry of science than to the domain of philosophy. 

 The heroic and polished lines of Darwin, however, 

 so happily express the subject of my paper, that no apology 

 is needed in quoting them before a Society which is both 

 literary and philosophical : — 



' ' Roll on, ye stars ! exult in youthful prime, 



Mark with bright curves the printless steps of Time ; 



Near and more near your beamy cars approach, 



And lessening orbs on lessening orbs encroach ; 



Flowers of the sky ! ye, too, to age must yield, 



Frail as your silken sisters of the field ! 



Star after star from heaven's high arch shall rush, 



Suns sink on suns, and systems systems crush, 



Headlong, extinct, to one dark centre fall, 



And Death, and Night, and Chaos mingle all ! 



Till o'er the wreck, emerging from the storm, 



