I20 SCIENCE AND IMMORTALITY 



through space, is picking up millions of meteorites ; 

 and the meteoric hypothesis supposes that the 

 solar system was formed in bygone ages by the 

 accretion of meteoric swarms, and that the nebulae 

 at present seen in the heavens are meteoric swarms, 

 which are growing into stars and planets. " A 

 meteoric swarm," says Miss Agnes Clerke, " may 

 be defined as a rudely globular aggregation of small 

 cosmical masses revolving, under the influence of 

 their mutual attraction, round their common centre 

 of gravity." They would circulate in aU planes 

 and would constantly collide, with the result that 

 certain of them would be brought to a standstill 

 and would condense as a central nucleus, which, 

 owing to the heat produced by gravitation and 

 collision, would be in a liquid or gaseous state, 

 whilst others, compelled by collision and elimination 

 into orbits with the same direction, v/ould revolve 

 as satellites round the central mass. The formation 

 of planets would seem to require original inequalities 

 in the density of the swarm ; but once their nuclei 

 were formed, they might easily increase in size by 

 a process of accretion, for they would attract, as 

 does the earth, meteoric material. 



According to this form of the theory, the outer 

 planets would be the larger, because they would 

 attract most material, while the inner ones would 

 be smaller, because the sun would, so to speak, 



