670 EDITORIAL 



It seems a debatable question if such a large proportion of the added mate- 

 rial was necessarily dust-like and capable of being weathered, sorted, and 



distributed by the primitive atmosphere and ocean In fact, from 



this beginning of earth-growth the preponderance of the evidence appears to 

 the writer to be against those sub-hypotheses which Chamberlin has followed. 

 This evidence, its bearings, and conclusions wiU form the following parts of 

 this article. It will be of ultimate value to both hnes of argument that each 

 may be weighed against the other 



It appears to the writer that the chemical character of the igneous rocks, 

 the limited depth of density variations in the crust, the limited amount of 

 salt in the sea, the rotation period for the moon and planets, all point to a 



molten condition of the earth at the completion of its growth The 



questions raised by this conclusion are: What mode of growth would have 

 favored the molten state and how far did this precede the beginning of the 

 geologic record as given by the oldest rocks exposed at the surface of the globe ?' 



Barrell then proceeds to discuss in terms appropriate to a 

 lecture rather than to an analysis, as the occasion demanded, the 

 significance of the planetoids, the indications of primordial tidal 

 retardation, and the deductions which may be drawn from the 

 limited amount of oceanic salt as to the age of the ocean. Con- 

 densed though it is, the argument is too long to be quoted here, 

 but the description of the early stages of the earth, as Barrell 

 conceived them, sheds light upon the tendency of his mental 

 development : 



The indications of primordial tidal retardation and the limited amount of 

 salts in the sea both point to the conclusion that the earth was molten at the 

 completion of its growth. The molten state suggests a rapid earth-growth due 

 to an original clustering of the matter whose convergence built up the planet. 

 Larger nuclei, hundreds of miles in diameter, and smaller ones comparable to 

 the planetoids, moved in elliptic and nearly intercepting orbits. Mutual 

 perturbations kept modifying these orbits and providing new chances for 

 collisions, union, and growth. Such collisions led to a development of energy 

 of impact sufi&cient to produce in the growing earth a molten state at least in 

 the outer portions. The earth kept growing at the same time by sweeping up 

 large quantities of finer material, but a molten state suggests that the greater 

 growth was due to the infall of the larger nuclei. Finally but one outstanding 

 nucleus, the moon, was left beside the earth, and the earth-moon system 

 attained a condition of stability and completed growth. 



After describing the state of the molten globe, which he con- 

 ceives to have been surrounded ''even in its molten stage by an 



^ The first of a group of lectures delivered before the Yale chapter of Sigma Xi 

 during the academic j^ear 1916-17, entitled "The Evolution of the Earth and Its 

 Inhabitants. The Origin of the Earth," by Joseph Barrell. 



