August 18, 1916] 



SCIENCE 



241 



of other molecules and curving back again 

 under the pull of the earth's gravitation into 

 the denser atmosphere. The action is like that 

 of particles of water splashing back in a foun- 

 tain or like the spray from an effervescing 

 liquid. This attenuated zone in which the 

 molecules describe appreciably curved paths 

 between molecular collisions is named the 

 Krenal atmosphere. Beyond it, but still within 

 the spheroid of control, must lie a zone which 

 has come to be inhabited by molecules moving 

 in elliptic orbits in every direction about the 

 earth and moving with considerable freedom 

 from impact. This Chamberlin names the 

 orbital atmosphere. He shows how the several 

 atmospheres are related, giving and taking 

 molecules, and how the orbital atmosphere of 

 the earth merges into the orbital atmosphere 

 of the sun. Following this constructive argu- 

 ment is a destructive argument, showing how 

 the Laplacian hypothesis fails to meet the re- 

 quirements of the nature of gases. 



This is an illuminating chapter. It shows 

 how, in sweeping up the planetesimal matter, 

 immediate and direct impact with the body of 

 the earth was not necessary. It will be found 

 suggestive also in relation to the later history 

 of the atmosphere. The moon lies far within 

 the zone of the orbital atmosphere and gases 

 given off by the moon during its history would 

 thus be added to the earth rather than diffused 

 into the outer space of the solar orbital atmos- 

 phere. As an agent for supplying CO, to the 

 earth's atmosphere during times of quiescence 

 of terrestrial igneous activity this may pos- 

 sibly be a factor not to be wholly ignored, 

 though always small. 



Chapter II. is on Vestiges of Cosmogonic 

 States and Their Significance. In the struc- 

 ture of the solar system and in the nature of 

 the earth is an autobiography of genesis. 

 These are the material records, but equally if 

 not more important, Chamberlin points out, 

 are the dynamic records. In rotations, revolu- 

 tions, and other relations are found automatic 

 vestiges of creation; difficult to interpret, per- 

 haps, but rigorously definite if we but under- 

 stood their evidence. The dynamic vestiges 

 in the sun are found first, in the inclination of 



its plane of rotation to the mean plane of the 

 planetary orbits; second, in the enormous pre- 

 ponderance of mass in the sun, the enormous 

 preponderance of moment of momentum in the 



Chapter III. is entitled The Decisive Testi- 

 mony of Certain Vestiges of the Solar System. 

 By these vestiges the Laplacian hypothesis is 

 tested and found wanting. The less specific 

 hypotheses, including that of Kant, hardly 

 lend themselves to rigorous testing and there- 

 fore can not be regarded as working hypotheses. 



The following chapter is given the name of 

 Futile Efforts. It records the results of in- 

 quiries by the author along other lines than 

 those of the Laplacian hypothesis. These other 

 lines were found also to lead to unsatisfactory 

 results, but they pointed the way to the general 

 direction in which a successful hypothesis 

 must probably lie. Especially they pointed to 

 spiral nebula? as dynamically more promising 

 forms. 



Chapter V. is entitled The Forbidden Field. 

 The direct rotation of the planets about their 

 axes had been thought to forbid any hypoth- 

 esis which sought to integrate the planets from 

 particles scattered in a zone and in free orbital 

 motion about the sun. This is shown to be 

 true however, as demonstrated by Moulton, for 

 a system of circular orbits only. For elliptical 

 orbits the distribution of matter in the region 

 of growth may readily be such that the con- 

 centration into a nucleus would engender a 

 direct rotation. This field of hypothesis is 

 therefore no longer forbidden. 



But how shall be produced such a primal 

 state as that postulated in a slowly revolving 

 central sun with but little moment of momen- 

 tum surrounded by a small amount of orbital 

 matter revolving nearly in a plane, dispersed 

 over wide limits, and possessing a relatively 

 enormous moment of momentum? This prob- 

 lem is taken up in Chapter VI., entitled Dy- 

 namic Encounter by Close Approach. The 

 volume of a star represents a balance between 

 expansional and condensational forces acting 

 on a vast body of gaseous nature. On the 

 approach of two stars their mutual gravitation 

 would produce tidal forces diminishing their 



