SPACE FULL OF SUBTILE MATTER. 273 



of the planetary motions, to suppose space in the 

 universe void of all matter," he overlooked the 

 existence of solar light, and even of that subtile 

 medium, the vibrations of which are supposed 

 by some to constitute light. That he did so from 

 authority, and without reflection, would appear 

 from what he says in another part of the same 

 work. " It cannot be doubted that there is matter 

 in motion through space between the sun, and 

 stars, and our globe." (Chem. Phil. p. 67.) 



There is no decisive evidence that any of 

 the ancient philosophers adopted the theory of a 

 perfect vacuum in nature. It was the opinion of 

 Bacon, that the ancient Pan, which all the 

 learned have regarded as an allegorical perso- 

 nation of the universe, " was represented as 

 hairy to denote the rays of things, because every 

 thing which acts at a distance may be said to 

 emit rays." (Wisdom of the Ancients.) 



It was also maintained by Lucretius, who is 

 regarded as the advocate of a vacuum, that sub- 

 tile streams are perpetually flowing from every 

 thing, without which bodies could not be disco- 

 vered at a distance.* (DeNaturaRerum, Book vi.) 



* That the regions of space are rilled with subtile matter can 

 no longer admit of doubt or controversy. By a train of analo- 

 gical reasoning, Pouillet has arrived at the conclusion, that the 

 quantity of heat annually received by the earth from the sun's 

 rays, is sufficient to melt a stratum of ice about forty-six feet in 

 depth over all its surface. (Elemens de Physique, Tom. ii. p. 

 204.) It therefore follows, that as the mean temperature of the 



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