THE BODIES OF SPACE, 

 4 7 10 16 28 52 100 196 



Merc. Venus. Earth. Mars. Jupiter. Saturn. Uranus. 



It will be observed that the first row of figures goes on from 

 the second on the left hand in a succession of duplications, or 

 multiplications by 2. There is here a surprising signification 

 of unity in the solar system. It was remarked, when this re- 

 lation was first detected, that there was wanting a planet cor- 

 responding to 28 ; the difficulty was afterwards considered 

 as overcome, by the discovery of four small planets revolving 

 at nearly one mean distance from the sun, between Mars and 

 Jupiter. 1 The distances bear an equally interesting mathe- 

 matical relation to the times of the revolutions round the sun. 

 With respect to any two planets, the squares of the times of re- 

 volutions are to each other in the same proportion as the cubes of 

 their mean distances, a most surprising result, for the discovery 

 of which the world was indebted to the illustrious Kepler. Sir 

 John Herschel truly observes "When we contemplate the 

 constituents of the planetary system from the point of view 

 which this relation affords us, it is no longer mere analogy 

 which strikes us, no longer a general resemblance among them, 

 as individuals independent of each other, and circulating about 

 the sun, each according to its own peculiar nature, and con- 

 nected with it by its own peculiar tie. The resemblance is 

 now perceived to be a true family likeness ; they are bound up 

 in one chain interwoven in one web of mutual relation and 

 harmonious agreement, subjected to one pervading influence, 

 which extends from the centre to the furthest limits of that 

 great system; of which all of them, the Earth included, must 

 henceforth be regarded as members." 



The tendency of ^ all the later discoveries has been to deepen 

 the conviction arising from the first, that the physical affairs of 

 the universe are all under the regulation of laws ; the forms, 

 the distances, the movements, the interdependencies, are deter- 

 mined in this, as distinguished from any arbitrary manner. 

 What, in the science of nature, is a law 1 It is merely the 

 term applicable where any series of phenomena is seen invari- 

 ably to occur in certain given circumstances, or in certain given 



1 Since that time many other members of this community have been 

 discovered. In 1846, a new planet of greater magnitude was discovered 

 beyond Uranus, and named Neptune. Till our knowledge of this stranger 

 is somewhat extended, the text may be left undisturbed. But it is 

 meanwhile worthy of remark, that the linear extent of the solar system 

 is now nearly double what it was supposed to be. 



