NATURAL PHILOSOPHY. 215 



economy. Extreme rarity would, indeed, prevent it from undergoing any 

 chemical change in the inter-planetary regions ; but it is compressed to a 

 much greater density about the vast spheres by which space is tenanted. 

 The atmospheres of this fluid enveloping the earth and the other large 

 planets, arc not sufficiently dense for chemical action, except in cases where 

 they receive an additional pressure from meteoric bodies sweeping through 

 them with wonderful rapidity. The evolution of light on such occasions 

 depends not only on the size and velocity of the falling mass, but also on 

 the direction in which it approaches the planetary surface ; and observation 

 shows that the most brilliant meteors move very nearly parallel to the hori- 

 zon. But around the sun a much stronger attractive force gives this ethereal 

 fluid the compression necessary for a constant chemical action, and a steady 

 development of light ; while the realms of space furnish inexhaustible sup- 

 plies of the luciferous matter, and impart perpetual brilliancy to the great 

 luminary of our system. It is not possible that the self-luminous condition 

 of the sun could be maintained by any combustible, or light-yielding matter, 

 of which it is composed. From a comparison of the relative intensity of 

 solar, lunar, and artificial light, as determined by Euler and Wollaston, it 

 appears that the rays of the sun have an illuminating power equal to that of 

 14,000 candles, at a distance of one foot ; or of 3500,000000,000000,000000,- 

 000000 candles, at a distance of 95,000,000 miles. It follows that the 

 amount of light which flows from the solar orb could be scarcely produced 

 by the daily combustion of 200 globes of tallow, each equal to the earth in 

 magnitude. A sphere of combustible matter much larger than the sun 

 itself should be consumed every ten years in maintaining its wonderful bril- 



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liancy, and its atmosphere, if pure oxygen, would be expended before a few 

 days in supporting so great a conflagration. An illumination on so vast a 

 scale could be kept up only by the inexhaustible magazine of ether dissemi- 

 nated through space, and ever ready to manifest its luciferous properties on 

 large spheres, whose attraction renders it sufficiently dense for the play of 

 chemical affinity. Accordingly, suns derive the power of shedding perpet- 

 ual light, not from their chemical constitution, but from their immense mass 

 and their superior attractive power. We thus obtain some definite knowl- 

 edge respecting the stupendous magnitude of the fixed stars ; and making 

 due allowance for their density, we may confidently pronounce the smallest 

 stellar body several thousand times greater than the globe we inhabit. This 

 theory gives considerable support to the views which many astronomers 

 maintain, on different grounds, in regard to the relative brilliancy of the 

 stars ; for it appears that, though the self-luminous occupants of space are 

 not necessarily equal in size, they differ much less than we might anticipate 

 from an acquaintance with the members of our planetary system. That the 

 light of the sun is furnished, not by its solid or liquid matter, but by its lu- 

 minous atmosphere, has been proved very conclusively from the observations 

 with Arago's polarizing telescope. There is also evidence that this lucifer- 

 ous envelop is constantly replenished by supplies of ether from space. The 

 sun's rotation assists in effecting this object by expelling the fluid from its 

 equatorial regions, and thus creating a corresponding influx at its poles. 



