Groundwork for Study of Megadiastrophism. 259 



and much loss of time in such aggregation, (2) what is 

 gained in the mass would be lost in the longer intervals 

 between infalls, and (3) the energy of infall largely takes 

 the form of mechanical dispersion. The larger meteor- 

 ites melt less proportionally than the small ones. The 

 great infall that produced Meteor Crater (Coon Butte) 

 gave a most impressive illustration of the largeness of the 

 energy dispersed in the form of side thrusts, of lateral 

 scattering of material, of outward radial dispersion by 

 the violent reactive explosion that followed the impact, and 

 of cooling in the'act of dispersion as shown by the vesicu- 

 lar state. On the other hand, the meagerness and evanes- 

 cent nature of the melting was equally surprising. 4 



According to the planetesimal hypothesis, the material 

 for the formation of the earth was erupted from the sun 

 under the stimulus of a passing body which drew the 

 projected matter into orbital courses while in its flight. 

 To be conservative let us assume that the erupted mass 

 of solar gas had only twice the diameter of the present 

 dense earth. The central mass of this matter would nor- 

 mally be projected vertically or radially from the sun's 

 center, and at the same time, as it issued from the sun, 

 would be subject to gaseous expansion, while it would also 

 be affected by eruptive dispersion and by internal motions 

 which would have a dispersing effect in general. The val- 

 ues of the expansional and dispersive effects are matters 

 of estimate, but it is easy to follow rigorously the vertical 

 projection of the central part. The distance projected 

 from the surface of the sun was roundly 215 times the dis- 

 tance of the erupted mass from the center of the sun when 

 it started ; hence the diameter of the erupted mass when it 

 reached its orbital distance would have been 430 times the 

 diameter of the present earth. To catch the meaning of 

 this, we must now consider the power of such a mass to 

 control itself against the competing attraction of the sun, 

 for this power of self-control determined the size and 

 mass of the collecting nucleus. No power of self-control 

 would develop in the erupted mass until after it had 

 passed outside the Roche limit of the sun. At the dis- 

 tance of the earth the sphere of control of the present full- 



4 Diastrophism and the Formative Processes : XIII. The Bearing of the 

 Size and Rate of Infall of the Planetesimals on the Molten or Solid State 

 of the Earth, Jour. Geol., vol. 28, pp. 686-95, Nov.-Dec, 1920. 



