THE LAW or EQUILIBRIUM 115 



great variety of bodies, argues that cause to be not blind and 

 fortuitous, but very well skilled in mechanics and geometry. 



In concluding this brief notice of the progress of physical as- 

 tronomy since the time of Newton in a few of its leading features, 

 we are naturally led to ponder on the great truth of the stability 

 and permanence of the solar system as demonstrated by the dis- 

 coveries of Lagrange and Laplace. In the present day, when 

 worlds and systems of worlds, when life physical and life intel- 

 lectual are supposed to be the result of general law, it is interest- 

 ing to study those conditions of the planetary system which are 

 necessary to its- stability, and to consider whether they appear to 

 be the result of necessity or design. It follows, from the dis- 

 coveries of Laplace, that there are three conditions essential to the 

 stability and permanence of the solar system, namely, the motion 

 of all the planets in the same direction, their motion in orbits 

 slightly elliptical, or nearly circular, and the commensurability 

 of their periods of revolution. That these conditions are not nec- 

 essary is very obvious. Any one of them may be supposed dif- 

 ferent from what it is, while the rest remained the same. The 

 planets, like the comets, might have been launched in different di- 

 rections, and moved in planes of various and great inclinations 

 to the ecliptic. They might have been propelled with such varie- 

 ties of tangential force as to have moved in orbits of great ellip- 

 ticity; and no reason, even of the most hypothetical nature, can 

 be assigned why their annual periods might not have been incom- 

 mensurable. The arrangements, therefore, upon which the sta- 

 bility of the system depends, must have been the result of design, 

 the contrivance of that omniscience that foresaw all that was fu- 

 ture, and that infinite skill which knew how to provide for the 

 permanence of His work. 



Another thing which doubtless has had a consider- 

 able retarding influence upon the trend of astronomical 

 thought, and which still makes its presence felt, is the 

 use of the same words celestial, heavens, heavenly, and 

 the like to designate both things spiritual and things 

 firmament al. The reader may judge for himself the 

 strength of this influence by a mental analysis of what 

 such, a phrase, for example, as " celestial mechanics" 

 means to him. I would respectfully ask whether it does 

 not connote for him a sort of transcendental mechanics, 

 a mechanics in some sort liberated from the rigid inflexi- 

 bility of our mundane natural laws and one, too, neces- 

 sitating the postulation of laws and principles peculiar to 

 cosmic as contradistinguished from terrestrial objects? 



