A NEEDED RECONSTRUCTION' OF TEE NEBULAR HYPOTHESIS. 371 



scheme of the universe the whole must be sys- 

 tematically combined. 



Kant, and, less thoroughly, Laplace, have 

 drawn the main outlines of the process by which 

 the solar system came into existence, and accord- 

 ing to which the properties common to the plan- 

 ets and moons are to be accounted for. The 

 theory, however, does not explain the differences 

 existing between those bodies with respect to 

 mass, distance from the sun — which, according 

 to the well-known law of Titius, is approximately 

 a geometrical progression — form of their orbits, 

 and velocity of their motion. And yet it is pre- 

 cisely on these differences, but particularly on 

 the distribution of the mass through space, that 

 the stability of the system rests. Hence we have 

 still to account, on the basis of natural laws, for 

 the teleological result of the process. Either we 

 must attribute to primordial matter, in addition 

 to gravity, some other property which shall ex- 

 plain the teleological result, or else we must as- 

 sume an important corollary of the principle of 

 gravity to have been overlooked by Kant. This 

 latter assumption is the only one that is scien- 

 tific. 



We have, therefore, to reconstruct the nebu- 

 lar hypothesis on the basis of the law of gravi- 

 tation, and to solve the following problems : 



1. The teleological mass-distribution of the 

 planets must be accounted for. It is not enough 

 to say that the sun contracted and gave off equa- 

 torial rings ; for the main point to be considered 

 is the fact that, at such and such distances from 

 the sun, planets of a certain proportionate ve- 

 locity and mass hold their courses, and that no 

 change could be made in any of these factors 

 without causing perturbations. 



2. Comets and meteorites must be brought 

 within the purview of the nebular hypothesis, and 

 their great numerical superiority over the planets 

 must be shown to be a necessary consequence of 

 the law of gravitation. When Laplace writes, 1 

 " Dans notre bypothese les cometes sont etran- 

 geres au systeme planetaire," without citing any 

 evidence to show that they are in reality of ex- 

 traneous origin, he appears simply to confess his 

 perplexity ; nor is it permissible to eliminate the 

 comets by arbitrarily assuming them all, both 

 those traveling in the same directiou with the 

 planets, and those traveling in the reverse direc- 

 tion, to have descended only at a later period 

 into our system from the regions of the fixed 



1 " Exposition du Systeme du Monde," p. 475. Paris, 

 1S46. — " In our hypothesis the comets are extraneous to 

 the planetary system." 



stars, to say nothing of the fact that by such 

 assumption we. do but push the problem farther 

 back. 



3. We have to explain why, notwithstanding 

 the enormous expansion of the primordial solar 

 sphere, the planets are not more numerous than 

 they are ; and further, why they are attended by 

 their actual number of planets, and neither by 

 more nor less. That we are warranted to propose 

 this question is plain, especially from the fact that 

 the number of moons accompanying a planet is, 

 as a rule, though with exceptions, in a ratio to 

 that planet's rotation velocity. Astronomy is 

 only a branch of mechanics ; and hence, when 

 we see, for instance, that though Mars rotates 

 with nearly as high velocity as the earth, it is 

 nevertheless moonless, we must directly conclude 

 that the moon of Mars, theoretically existent in 

 accordance with mechanical principles, must at 

 one time have existed in reality. 



As must always be done with phenomena 

 which, standing alone, are barren, we have now 

 to connect synthetically these three groups of 

 phenomena, which of necessity must be more or 

 less closely related to one another. 



That Mars's moon is wanting is a fact that by 

 itself says nothing, but it becomes very eloquent 

 when we connect it with the two other points of 

 the problem we have to solve. In the first place, 

 when we consider that in the formation process 

 of the solar system processes of elimination, too, 

 had a place, it appears allowable to assume elimi- 

 nation of once-existent satellites. And if now we 

 view these processes of elimination in connec- 

 tion with the phenomena spoken of in section 

 one, the two are found to throw light on each 

 other, and we are inevitably led to conclude that 

 the teleological distribution of mass in the solar 

 system is the result of processes of elimination 

 whereby those planets and moons have been dis- 

 placed, which deranged the mechanism of the 

 system. 



Not only does this explanation deduce from 

 the law of gravitation the teleological phenomena 

 of the solar system, it furthermore proves itself 

 to be the only just explanation by its conformity 

 to the laws of logic, which require us to look on 

 such phenomena not as entering Nature already 

 fashioned and shaped, but as being the results 

 of a process of development. And if science, 

 which, as it has been supposed, spurns the idea of 

 teleology, would nevertheless demonstrate the 

 possibility of teleological results, it can do so 

 only by assuming a process of indirect selection ; 

 and this in turn is conditioned on the impossi- 



