THE EARTH AT ITS BEGINNING 



great nebulae which the telescopes reveal to us order 

 would be evolved. Two things would at once begin to 

 happen, since in the Universe nothing stands still. The 

 fiery mist would be giving out heat all about it, sending 

 out heat-waves as a fire or a red-hot poker will do. The 

 red-hot poker cools ; so, too, would the fiery nebula. 

 Then the nebula would begin to condense ; not quite in 

 the same way that a cloud of steam does, for it would be 

 whirling all the time, and its fiery particles would be all 

 trying to fall inwards, just as anything dropped from our 

 hands tends to fall towards the centre of the earth. As 

 this whirling mass of gas condensed some great masses 

 of it would become detached, and would begin to enjoy 

 separate existences of their own. 



Let us imagine, for the sake of argument, that a mass 

 of gas vast enough, when it condensed, to form the earth 

 itself became detached from the parent nebula. Suppose 

 we follow its history. At first it may have been a globe 

 hardly distinguishable from a whirling flame. In bright- 

 ness it was like the Sun, and like the Sun, it was 

 covered with elemental gases. It was, in fact, in its 

 earliest days a sphere of gas continually giving out 

 heat, and continually cooling, till from a sphere 

 like the Sun it became a ball like Jupiter. It had 

 an intermediate stage when its gases were condens- 

 ing into liquids, as steam condenses into water ; for 

 though the nebula as a whole was hot it was always 

 travelling through cold space. Gradually the earth 

 became partly liquid and partly gas. For millions of 

 years it continued to revolve as a ball of liquid still 



94 



