mica : and, what adds to the wonder is, that, towards the 

 base of this deposit, there Hes a thin band of rock, not more 

 than an inch in thickness, composed entirely of fish remains, 

 bones, scales, teeth, and coprolites, pressed down into a hard 

 solid mass: Avhile a similar bed, scarcely as thick, occurs a 

 little higjier up. And Jiow can all this have come about ? 



To understand it we must know something of the world 

 live on. 



Originally a vast nebulous mass, which gradually con- 

 tused, it is now, (as generally accepted,) a thin crust, some 25 

 liles thick at the most, resting on a molten fluid substratum, 

 under which, (as some think,) lies a solid rigid core. Now a 

 thin crust over a fluid cannot be stable, and the surface there- 

 fore of our globe is for ever changing, rising here and sinking 

 there, rising in parts where denudation makes it thinner, and 

 sinking in regions where, through volcanic action, or the pour- 

 ing on of the debris of large rivers, and other similar causes, 

 matter is being piled up and the strata thickened. 



And, in the region we are considering, action of this 

 latter kind had taken place. The older strata had begun to 



sink, and, by degrees, the waters of a great ocean, coming up 

 from the south over France, were let in upon them. The 

 inland lake became an arm of the Liassic sea, and the Rhoctic 

 beds were formed. 



I 



It must not be supposed, however, that all this took 

 lace suddenly. It was the result of no convulsion of nature, 

 no rending of the rocks and inrush of the sea, but it came 

 about quietly and imperceptibly, occupying as much time, pro- 

 bably, as would be necessary for so great a change in our 

 own days. First, as the land continued to sink, would come 

 the want of drainage, then the morass, then the tidal wash, 



