34 HEAT OF THE EAETH. 



from its primitive condition into the state in which 

 it now is, through a process of gradual cooling, 

 at least of the outermost crust of the red-hot 

 mass; — a supposition, in fact, which rests upon 

 several grounds, which agree in warranting its 

 assumption. 



The fact that the conditions of the earth are 

 still liable to change, favours the conjecture that 

 the globe itself could not have been created, just 

 as we see it now, ready-made, but that it must have 

 arrived by very slow steps at its present state. 

 The assumption of the spherical shape, which is 

 that of perfect equilibrium for solid particles at- 

 tracting each other, presupposes, as a necessary con- 

 dition, a great freedom of motion among those 

 particles, that is, of course, a fluid state. This 

 fluidity of our globe, by the very nature of most 

 of its elements, at least so far as we know, can 

 only be brought about by a very high temperature 

 — by a temperature about as high as that which, 

 doubtless, the sun still maintains* Again the flat- 

 tening towards the poles, which affects, as you are 

 aware, not only the water, but also the dry land, 

 would without this assumption be unaccountable. 

 Without it we must have considered it as most 

 wonderful, that this deviation from perfect round- 

 ness should chance to be exactly as great as, on 

 the assumption of original liquidity, it must have 

 been. 



