The Earth and its Early History 



Hypothesis. His view is that a central body, possibly 

 cold and dark, formerly contained all the matter now 

 distributed between the Sun and the planets and satellites 

 which now constitute the Solar System, and that this 

 central body was broken up by the attractive force of 

 a similar body, which, in the course of its wanderings 

 through space, came sufficiently near to produce disrup- 

 tion owing to tidal stresses. 



By far the greater part of the matter would appear 

 to have remained in the central body, while two great 

 arms were thrown out on opposite sides of the ancestral 

 Sun, which by the friction was raised to a high tempera- 

 ture and caused to glow. The arms consisted of many- 

 sized fragments of solid matter, together with much 

 gaseous matter, the solid fragments being scattered 

 quite irregularly through the arms, here in dense swarms, 

 there few and far between. 



The arms eventually became coiled in spiral form, 

 producing a spiral nebula similar to those which have 

 been revealed by our telescopes in enormous numbers 

 throughout the Universe. 



It has been proved that, under the conditions 

 supposed, the various masses thus scattered through 

 surrounding space by the disruption of the ancestral Sun 

 would soon come to travel in elliptic orbits round the 

 remnant of the central mass. 1 



The matter in the arms of spiral nebulae is known to 

 be distributed irregularly, there being many knots in the 

 arms. The knots in the arms of the Solar Nebula are 



1 For further particulars of the Planetesimal Hypothesis the reader is 

 referred to volume ii. of Chamberlin & Salisbury's Geology^ where a full and 

 lucid account of it will be found. 



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