DIASTROPHISM AND THE FORMATIVE PROCESSES 477 



side of gas accumulation, while in the lower part the dominant 

 effect lay in the dissipation of all gas. In the middle ranges there 

 was a closer approach to equipoise between these extremes and 

 hence to a mixed product of the medial order. It is thus clear that 

 the genetic processes, however alike basally, were capable of giving 

 such different results as to make it necessary to study with care 

 and patience the balancings between opposing influences and the 

 differential effects of the shifting of these balances. 



THE CRITICAL CONDITIONS THAT CONTROLLED THE PASSAGE OF THE 

 NUCLEI INTO COLLECTING CORES 



The original diversity of the nuclei is assigned to differences in 

 the impulses imparted by the solar eruptions. The evolution of 

 the nuclei, after being launched on their several careers, was 

 critically dependent on the dynamic properties which they inherited 

 individually. These now require attention. We need not dwell, 

 however, on the giant gaseous planets, for they do not fall within 

 the range of our present problem, nor do they seem to have ever 

 passed through the more critical phases of the processes we are 

 about to consider. They probably had, at the outset, nuclei 

 massive enough to hold essentially all their own gases in spite of 

 their molecular activity and to retain essentially all alien molecules 

 that plunged into them.^ 



To cover the whole field of the known solid bodies in a repre- 

 sentative way, Table II is introduced. It gives certain essential 

 dynamic properties for ten typical bodies, four natural and six 

 ideal, so selected as to represent at convenient intervals the whole 

 range from the earth — the largest known solid body — down to a 

 ten-mile planetoid. Dr. W. D. MacMillan has been kind enough 

 to make the computations for this table. 



It seems improbable that the nuclei of the earth, Venus, Mars, 

 or the moon, even at their smallest stages, were so diminutive as the 

 lower orders of ideal bodies in Table II, but these very small bodies 

 are even more serviceable than larger ones in illustrating the critical 

 conditions that attended their formation and measurably that of 



' The inevitable loss of such molecules as attained very exceptional speeds is 

 neglected throughout this discussion. 



