THE GENESIS OF WORLDS. 77 



and its allied forces are only effects, and the subject is and can be 

 only matter. There is no physical truth better established than 

 that the forces can exist only where matter is in some form. It 

 is not essential that this form of matter be subject to the ordinary 

 laws of gravitation. The probability is that it differs entirely 

 from anything that we have experience of. It would seem that 

 the atoms composing the ether of space, instead of attracting 

 each other like those of ordinary matter, must repel each other. 

 At least this supposition would account for what there is remark- 

 able in connection with the ethereal medium. But whatever 

 theories we may adopt in regard to it, this is certainly true, that 

 the revolutions of the heavenly bodies must be continually open- 

 ing passages through it, and that a certain part of the force of 

 those revolutions must be expended in pushing it aside. The 

 centrifugal force is thus lessened, and the bodies are drawn nearer 

 to the sun. In consequence, the periods of their revolutions 

 are shortened. This has not as yet become noticeable in the case 

 of the planets, from the fact that the slow contraction of their 

 bulk by the loss of internal heat through volcanoes, thermal 

 springs, and other sources, has the contrary effect of increasing 

 the velocity of revolution, and thus counterbalancing the retard- 

 ation by friction. The fact that the two effects are thus nearly 

 counterbalanced, proves the retardation, for otherwise we know 

 that the acceleration would be observable. In the case however 

 of the light cometary bodies, it has been shown that they suffer 

 a very considerable retardation in their passage through space. 

 Encke's comet formerly came regularly back into the iield of 

 the earth's orbit once in every three years, but with a period 

 shortened six hours each time. The whole planetary regions 

 seem to be filled with collections of matter star-dust and mete- 

 orites. They are all revolving about the sun in eccentric orbits, 

 and are doubtless slowly circling toward it. The zodiacal light 

 is supposed to be only an immense aggregation of this material. 

 Thus the thickening stratum, as these strange bodies draw near 

 to the sun, shows that they are all slowly gathering to that great 

 center of attraction. 



