THEORY AND HISTORY OF THE SUN. 157 



In order to understand how it comes about that, in 

 the formation of a cosmic system, the body which 

 serves as the centre of attraction must have become 

 a fiery body, notwithstanding that the other globes within 

 the sphere of its attraction remained dark and cold bodies, 

 we have only to recall the mode in which a cosmic 

 system is produced. This has been sketched circum- 

 stantially in the preceding pages. In the widely extended 

 space in which the diffused elementary matter adapts 

 itself into formations and systematic motions, the planets 

 and comets are formed only from that portion of the 

 elementary matter that sinks to the centre of attraction, 

 and which has been determined by the fall and the 

 reciprocal action of the whole of the particles, to that 

 delimitation of their direction and velocity which is 

 required for their revolution. This portion of the primi- 

 tive matter, as has been already shown, is the least 

 condensed of the whole mass of the obliquely sinking 

 matter, and is, indeed, only the remainder of the denser 

 kinds of matter which have been able to attain that 

 degree of exactness in their motions through the resist- 

 ance of other kinds of matter. In this mixture there are 

 found floating kinds of matter of predominant lightness, 

 which, being impeded by the resistance of space, do not 

 by their fall attain to the proper rapidity of the periodic 

 revolutions, and which, in consequence of the feebleness 

 of their impulsion, are wholly thrown down to the central 

 body. And because these lighter and volatile portions 

 are also the most active in maintaining fire, we see that, 

 by their accession, the body which is the centre of the 

 system thus obtains the advantage of becoming; a flaming 

 ball, or, in a word, becomes a sun. On the other hand, 



