EECENT COSMOGONIES 251 



back to the sun on about the same spot whence it had is- 

 sued ; other matter being drawn forward somewhat more 

 strongly, fell back also, but angularly, giving, as it were, 

 a fillip to the sun, thereby starting or accelerating his 

 axial rotation ; while the great bulk of the matter was 

 pulled forward with sufficient force to lift it into orbital 

 paths more or less elliptical. Once given such motion, 

 under Newtonian interpretation, they would retain it 

 permanently, and in the course of time the larger nuclei, 

 which would inevitably have resulted, would aggregate 

 to themselves the minute particles, or " planetesimals. " 



Doctor Chamberlin recognizes that, in the first in- 

 stance, all the orbits would probably be very elliptical, 

 but opines that a composite of many of them ( a condi- 

 tion which would eventually be brought about by a mul- 

 tiplicity of collisions) would no doubt prove more nearly 

 circular. Hence it is, he says, that the orbits of the plan- 

 ets are only slightly eccentric, whereas those of the as- 

 teroids, which have (because of their smallness) experi- 

 enced only relatively few collisions, are quite capricious 

 and, as further corroboration, he points to the fact that 

 Mercury and Mars, the smallest among the planets, have 

 the most eccentric orbits of all. Proceeding further, 

 Doctor Chamberlin argues that, besides thus accounting 

 for the circularity of the orbits of the planets, the plan- 

 etesimal impacts upon the nucleating bodies probably 

 gave rise to the direct rotations, and, furthermore, doubt- 

 less generated such retrograde rotations as are known to 

 exist within the system. 



Doctor Chamberlin seeks to explain the recurrence 

 of ice ages in the long past, not by variations in the solar 

 temperature, but by the periodicity of terrestrial crustal 

 convulsions. For this he prepares the ground by deny- 

 ing the sufficiency of the impact hypothesis to explain any 

 part of the earth's present internal heat, and, instead, de- 

 rives this heat partly from the bodily contraction of the 

 planet and partly from radio-activity. He argues, that 

 during periods of quiescence this internal heat accumu- 

 lates and, finally, having gained sufficient strength, forces 



