14 T. C. CHAMBERLIN 



by similar dynamic environment. It does not seem naturalistically 

 probable that arbitrary variations of sufficient moment to affect 

 the average order of results could have entered into these combi- 

 nations so closely analogous in general nature. It is well recognized 

 that under the law of probabihties a multitude of random contribu- 

 tions, uniting under common conditions, give closely concurrent 

 averages even though the individual contributions may be highly 

 variant. It will be seen from the discussion in the succeeding 

 article that a very definite law probably presided over the proportion 

 of the inherently heavy to the inherently light material which 

 entered into the formation of the four bodies compared. Taking 

 then their systematic organization for granted for the time being, 

 the following tentative points are to be noted: 



I. The total shrinkage of the earth implied by the comparisons 

 is very large. A circumferential shrinkage of 4,555 miles in a 

 putative growth from a moon stage by the addition of moon-stuff 

 is certainly large. A similar shrinkage of 3,883 miles in a growth 

 from a Mars stage by the addition of Mars-matter is quite as 

 notable; and a shrinkage of 1,112 miles in a growth from a Venus 

 stage — a stage in which 80 per cent of growth has already been 

 attained, while the material added has the high density of Venus — ■ 

 is even more remarkable. These large shrinkages are ample to 

 meet all the demands that gave rise to the inquiry and leave a good 

 working margin beside. 



II. Since the four bodies were treated as spheres, the computed 

 shrinkages apply to all great circles, meridional, oblique, or equa- 

 torial, equally. The special deformations that may be assignable 

 to changes in the rate of rotation are not here included. There 

 was probably always some equatorial bulging and polar flattening, 

 but the geological evidence does not seem to imply that defor- 

 mations of this class were essentially greater during the early ages 

 than they have been during the later ages.^ The large shortening 

 in meridional circles given by the computations satisfies the require- 

 ments of the Archean crumplings and related phenomena of the 

 high latitudes, which seem to be essentially as great as those of low 

 latitudes.^ 



>"The Tidal and Other Problems," Publication No. 107, Carnegie Institution of Washington 

 (1909), p. SI- 

 " Loc. cit. 



