THIRD CHAPTER. 



OF THE ECCENTRICITY OF THE ORBITS OF THE 

 PLANETS AND THE ORIGIN OF THE COMETS. 



IT is not possible to regard the comets as a peculiar 

 species of heavenly bodies entirely distinct from the race 

 of planets. Nature works here as elsewhere by insensible 

 gradations; and in passing through all stages of change 

 it connects remote qualities with those that are near, 

 by means of a chain of intervening members. In the 

 case of the planets, their eccentricity is a consequence 

 of a deficiency in that effort by which nature strives to 

 make the planetary movements exactly circular, but which 

 it can never completely attain on account of the inter- 

 vention of diverse circumstances ; and the conditions are 

 such that the deviation is greater at greater distances than 

 at near. 



This modification passes through a constant gradation, 

 by all possible degrees of eccentricity, from the planets 

 at last to the comets. And although this connection 

 seems to be interrupted at Saturn by a great gulf which 

 completely separates the race of comets from the planets, 

 yet, as we have remarked in the first part of this essay, 

 it is probable that there may be other planets beyond 



