DIASTROPHISM AND THE FORMATIVE PROCESSES 493 



complete dispersion, such complete dispersion springing variously 

 from inherited motions, from thermal convection, from molecular 

 activity, or from divers combinations of these. If, as the natural- 

 istic method insists, the solid bodies themselves are to be taken as 

 the vestiges of the actual process, the observed range in size tallies 

 with our previous suggestion that the limits which permit success 

 along this line are actually reached in the existing series. Appar- 

 ently our best method, then, is to consider the whole range for the 

 sake of learning what were the inhibiting conditions at the vanish- 

 ing end. We may then the better form an opinion of what probably 

 took place nearer the middle of the great series where our interest 

 chiefly lies. A naturalistic method is much to be preferred to a 

 deductive treatment, for the latter is embarrassed by the multitude 

 of possible assumptions. In pursuance of the naturalistic method 

 let us seek some telltale feature that has been actually realized 

 and make that our base of procedure. The series of atmosphereless 

 bodies furnish such a base. They tell us within what bounds the 

 inhibiting limit lay for such gases as form atmospheres. In passing 

 through the actual conditions of evolution they have been stripped 

 of all gases as light and active as nitrogen or oxygen. Further 

 than this, they have maintained that condition since. The condi- 

 tions must probably have been most exacting in the hot genetic 

 stages, and there has been chance for recovery since. Their present 

 condition, with some reservations, may be taken as an approximate 

 indication of equilibrium conditions. The graded list in Table I 

 giving the range of planets, planetoids, and satellites, from the 

 earth down, may be found convenient here. 



The case of atmospheric gases being thus approximately deter- 

 minate, it remains to find at what stages the gases or vapors of 

 such stony and metallic substances as make up the earth, meteor- 

 ites and like bodies, would encounter their inhibitive limit. The 

 basis for this lies in the fact that the molecular velocities of mole- 

 cules vary inversely as the square roots of their molecular weights. 

 The heavier we assume the molecules to be the more conservative 

 our conclusions, so let us assume that the small nuclei were com- 

 posed of molecules as heavy as those of the leading minerals in 

 meteorites. The square roots of the molecular weights of the nine 



