OUR MOLTEN GLOBE 57 



APPENDIX 



In an interesting article {Science, June and July, 1899) 

 Mr. T. C. Chamberlin has discussed the theory of the 

 formation of our earth by meteoric accretion instead of 

 by the condensation of a gaseous or liquid ring left be- 

 hind by the contracting sun ; and he suggests that the 

 process of accretion might have been so slow that the heat 

 produced would never have been sufficient to produce a 

 liquid globe, and that the somewhat irregular mass of matter 

 partially solid or in parts liquefied, would better explain 

 many geological phenomena and might lengthen indefi- 

 nitely the period of cooling, so as to obviate the difficulty 

 as to a too limited period of solidity given by the calcula- 

 tions of Lord Kelvin. 



As the meteoritic theory of the universe is now becoming 

 widely accepted as being in accordance with a vast body 

 of facts, and offering none of the almost insuperable 

 difficulties presented by the nebular hypothesis, it may 

 be thought that it contradicts the theory of a liquid 

 interior so strongly supported by the observations and 

 calculations summarized in the present chapter. This, 

 however, is by no means necessarily the case. It may 

 be that the rate of meteoric accretion has greatly varied. 

 At first it may have been so slow, and the impact of 

 the constituent meteors may have been so comparatively 

 weak owing to the slight force of their mutual attrac- 

 tion, that the nascent globe long remained solid. But 

 when it had grown to a considerable bulk its attractive 

 force would render the impact of the falling meteors so 

 great as to produce partial liquidity. If at this stage the 

 larger proportion of the contents of the meteoric ring 

 were drawn in to the growing mass, and especially if 

 several large aggregations of matter successively fell in, 

 the outer portions of the globe might become liquid while 

 the interior remained solid, though imperfectly aggregated, 

 and with numerous hollows filled with gases or liquids. 

 It may, therefore, be the case that under the thin crust 



