8 FROM NEBULA TO NEBULA 



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. 



And a half century later Young says (G. A., p. 566) : 



In the present state of science many of the questions thus 

 suggested seem to be hopelessly beyond the reach of investigation, 

 while others appear like problems which time and patient work 

 will solve, and others yet have already received clear and decided 

 answers. In a general way it may be said that the condensation 

 and aggregation of rarefied masses of matter under the force of 

 gravitation; the conversion into heat of the {potential) "energy 

 of position" destroyed by the process of condensation; the effect 

 of this heat upon the contracting mass itself, and the radiation 

 of energy into space and to surrounding bodies as waves of light 

 and heat these principles contain nearly all the explanations that 

 can thus far be given of the present state of the he< venly bodies. 



We see that our planetary system is not a mere Accidental ag- 

 gregation of bodies. Masses of matter coming haphazard to- 

 wards the sun would move as comets do, in orbits, always conic 

 sections to be sure, but of every degree of eccentricity and in- 

 clination. There are a multitude of relations actually observed in 

 the planetary system which are WHOLLY INDEPENDENT OF GRAVI- 

 TATION AND DEMAND AN EXPLANATION. 



