ASTRAL PERIOD 357 



densation of the vapours, the heat generated by the collisions, as 

 the broken ring was gathered into a mass, would suffice to raise 

 the temperature and liquefy or vapourize the mass. By revolution 

 the nebulous masses would assume a spheroidal shape and become 

 planets. The central mass of the original nucleus forms the sun, 

 which is still in an intensely heated, incandescent state. 



This is not the place to discuss the evidence for an astronomical 

 speculation, but we may regard it as in the highest degree probable 

 that when our earth first began its separate existence, it did so as 

 a globe of fused or even vaporous material, in which the various 

 substances arranged themselves very much in the order of their 

 density. This conclusion is much strengthened by the character 

 of the globe itself. The specific gravity of the earth as a whole 

 somewhat exceeds 5, while that of the rocks on the surface ranges 

 from 2.5 to 3, which shows that the interior of the earth is much 

 denser than its outer portion. We have already learned that the 

 earth's interior is still highly heated, and its shape, that of an 

 oblate spheroid flattened at the poles, is that which would be 

 assumed by a rotating liquid or plastic body. 



For long ages the earth must have continued as a glowing star, its 

 " astral period" but gradually an outer crust was formed by the slow 

 cooling of the surface. How often this thin crust was broken up 

 and remelted and formed again, we have no means of knowing, but 

 eventually a solid, permanent crust was established and thickened 

 by additions from below, until, by the combined effects of cooling 

 and enormous pressures, the globe has reached its present condi- 

 tion, whatever that maybe (see p. 32), Even after a solid crust 

 had been formed, it must' have long remained so hot that no water 

 could condense upon its surface. All the water of the oceans must 

 then have been in the atmosphere, increasing many fold the weight 

 of the latter and the pressure which it exerted upon the earth's sur- 

 face. Owing to this great pressure the first condensation of steam 

 must have occurred at temperatures far above the boiling-point of 

 water for the present atmospheric pressure (212 F.). Superheated 

 water is an agency of extreme power in destroying and recombining 

 materials, and the earliest boiling oceans must have set up very 



