KANT AND EVOLUTION 549 



formations which are the seeds of the future planets. For the particles, 

 as they move round the sun in parallel circles and at not too great a 

 difference of distance from the sun, are, by the equality of their parallel 

 motion, almost at rest with respect to one another, and thus the attrac- 

 tion of those particles which are of a higher specific attraction imme- 

 diately produces an important effect, namely, the collection of those 

 nearest one another so as to form a body which, in proportion to the 

 growth of its mass, extends its attraction farther and draws elements 

 from a wide region to unite with it in its further formation." 



It must be left to mathematicians and astronomers to assess the 

 precise merits of these speculations in comparison with those of Kant's 

 predecessors and successors in the same undertaking. But as to the 

 historic affinities of Kant's hypothesis the facts seem so clear that even 

 a layman may pronounce upon them. The Kantian scheme is as dif- 

 ferent from Laplace's as any post-Newtonian cosmogony could well be. 

 For it does not start with a gaseous, rotating, heated nebula; it does 

 not explain the direction of revolution and rotation of the planets as 

 derived from the rotation of a mass formerly cohering with that now 

 constituting the sun; it does not regard the planets as having ever 

 formed part of any such mass. It is well-known that the rings of 

 Saturn suggested the most characteristic feature of Laplace's theory. 

 Kant has a chapter explaining these rings much as Laplace does ; but 

 he expressly insists that " the ring which surrounds Saturn was not 

 acquired in the general way, nor has been produced by the universal 

 laws of formation which have ruled the whole system of the planets." 

 On the other hand, it is not quite exact to identify (as does Hastie 15 ) 

 Kant's system of planetary evolution with the meteoritic hypothesis of 

 Lockyer and G. H. Darwin. So far as I understand these matters, 

 Kant's cosmogony most nearly resembles an extremely recent doctrine 

 upon the subject — the planetesimal hypothesis of Chamberlin and 

 Salisbury. In the words of those authors : 



Under the typical form of that hypothesis it is assumed that the parent 

 nebula of the solar system is formed of innumerable small bodies, planetesimals, 

 revolving about a central gaseous mass much as the planets do to-day. The 

 evolution of the system consisted in the aggregation of these innumerable small 

 bodies into much fewer large ones. . . . The hypothesis, therefore, postulates no 

 fundamental change in the system of dynamics after the nebula was once 

 formed, but only an assemblage of the scattered material. The state of disper- 

 sion of the material at the outset, as now, was maintained by orbital revolution, 

 or, more closely speaking, by the centrifugal acceleration arising from revolu- 

 tion. 14 



15 "Kant's Cosmogony," 1900, p. lxxxiv. At this date, of course, the 

 planetesimal type of hypothesis had hardly been differentiated from the 

 meteoritic. 



"Chamberlin and Salisbury, "Geology," 1906, II., p. 38. The authors of 

 this theory have failed to recognize in Kant an early prophet of their own doc- 

 trine, and have referred to him, in the conventional manner, as having held a 

 hypothesis " somewhat similar " to Laplace's ( op. tit., p. 4 ) . 



