Proctors Astronomical 



tTnit 1a a pnlnfnl belief, making the Almighty God 

 give evidences th;it merely lead meu astray. And, 

 tberofore, when we find these facts in the solar system, 

 It Is natural and right for us our reasoning: powers not 

 being given to us for nothing .t is right for us to try 

 and conceive how that state of things arose. The 

 cctual probabilities are great against anything like 

 chauce distribution of the solar system, particularly 

 when we remember there are 142 primary and secondary 

 phmets, and when we take into account their motion 

 alone, each circling around t tie sun in the same direction. 

 The chan-o that one is going in one direction and the 

 next goiug in the same direction is only one chance out 

 of two, and the chance that a third would go in the 

 earne direction is ouly one chance out of four ; the 

 Chance that a fourth would go likewise is only one out 

 of eight; a fifth, one out of 16; so we must go on 

 doubling until we find that the chance of 142 planets 

 going around in the same direction I hope you will be 

 patient while I tell you the number is one in, 

 2,774,SCO,OUO,000,000,000,000,0),0;!0.000,000,000,000 > 000. [Laugh- 

 ter and applause.] But that is 'not all. The way in 

 which the planets travel is a fact in itself that seems to 

 Indicate a certain process of evolution by which they 

 have a particular motion. 



LAPLACE'S NEBULAR THEORY. 



Now if we consider the way in which that mo- 

 tion arose we are first led to the hypothesis of 

 the French astronomer Laplace. Laplace, in his ex- 

 plauatiou of this motion, had the idea that there 

 was a great nebulous mass having the sun in 

 the center, extending on either side far beyond the 

 present breadth of the path of the utte-mosr planet, 

 that is. a path of 5,000,000,000 miies diameter, and the nebu- 

 lous system of Laplace extended beyond that. That 

 mass was intensely hot and vaporous, and it was 

 rotating, and as the rotating mass contracted and it 

 began to rotate more rapidly, the result was that a ring 

 was thrown off by centrifugal force. In time the ring 

 would gradually break up, its parts would gradually 

 amalgamate; many parts would have different rates of 

 motion, and different parts would encounter each 

 other, and in the course of millions of ages there 

 would be an amalgamation into one mass, having 

 the same direction of motion that the nebulous mass 

 bad, and traveling around a center which waa 

 the sun. But as this minor mass went on contracting it 

 would follow the same law as the original body which gave 

 birth to it. It would go on contracting, and go round 

 more and more rapidly; perhaps it would throw off true 

 rings, which would become satellites. So the earth was 

 formed ; she turns on her axis in 24 hours in the same 

 direction, while she takes 3G5 days in going around the 

 eun. So it was with Jupiter and S iturn and all the 

 pi.ii.fits all iu rotation in the same direction. That 

 process would go on until one planet after another was 

 formed. And so it was that the solar economy, as we at 

 present know it, would arise. 



That is a rough account of the nebular hypothesis of 

 Laplace. It seems to me that there i3 great difficulty iu 

 laewayof accepting it. In the first place, we have 

 nothing to lead us to believe that a great nebular uiasa 



Lectures. 



41 



of so enormous dimensions and Px*TPm tonnifv ^...u'l 

 rotate as a whole or exist as a whole. Wo hav-j no evi- 

 dence to lead us to believe that the rings of Saturn are a 

 continuous solid. We know they could not exist an 

 nebulous rings, and we have now as the accepted 

 theory that they are a multitude of separate satellites 



that could not have existed as a whole and rotated as a 

 whole. 



Another point: That nebulous mass rotating by uni- 

 form process, if contracting, must give birth to a uni- 

 form system. There would be some law associating the 

 planets' distances with their dimensions, and that, as we 

 know, is far from being the cise. We have tliree parts 

 of the solar system the inner planets, the 

 asteroids, the outer planets. The sun is 751 times aa 

 large as the outer ones ; the outer ones over 200 

 times as great as the inner ones. Take any 

 one of these families, and we find apparently no law in 

 their arrangement. Among the ii;ner planets, there is 

 first Mercury, a very small planet; then Venus, very 

 much larger; then the earth, still larger, and dignified 

 with a moon ; but then we come down again to Mars, 

 which is a small planet. Then we have the asteroids, 

 more specks, 134 of tuem. Then take the outer family, and 

 there is still no progression. We have the largest of the 

 planets, Jupiter; then Saturn, also immense, and then 

 the planets Urauus and Neptune, about equal in size but 

 smaller than Jupiter or S *i:rn. Laplace's theory does 

 not explain why the famuy of least dimensions should 

 be iu the middle, and the larger one outside and the 

 smaller near the sun ; and we have no account of the 

 relations of these bodies by his theory, and only aa ex- 

 planation of the general facts first noted. 



ASTRONOMERS LIKENED TO A COLONV OP MAY-FLIES. 



We are led, therefore, to another theory, and I adopt 

 what appears to me a suitable method of illustrating it. 

 If we imagine a colouy of small insects, of the May-flies 

 or ephemera, which live but a few hours, and living in 

 and having as the center of their domain a large tree, 

 these ephemera are not able to ascertain anything 

 about that tree in their time of existence, as they live 

 but one day. But we may suppose them to be 

 reasoning beings, and that they have handed 

 down from one to another the discoveries made 

 by their ancestors, and they proposed to ascertain 

 in time, by exercising their intellectual powers, 

 the laws according to which the tree grew, and some- 

 thing of the future of the tree. They would trace bacfe 

 the history of the tree and arrive perhaps at some notion 

 by comparing that tree with others, and that it sprang 

 from a seed, and they would do as we do, and think that 

 was the beginning of all things, for this tree would bo 

 their universe. If they were told by some thoughtful 

 May-fly that the tree resulted from the contraction of a 

 great mass of vegetable matter, they might remain 

 satisfied with this notion for a long time, but 

 if they found by observing other trees that there were 

 no such vegetable masses contracting in that way, it 

 would bo just on their part to look to another theory, 

 and finding the process of growth, they would trace 

 tvac-k the process and say that it was the result of the 

 quite different process of tree-growth to that stage* 



