THE BUILDING OF AN ISLAND. 69 



to assume that it has been the case. That the limestone formation has orie- 

 inally been much thicker and much wider spread than we now find it is certain ; 

 but farther than that general assertion it does not seem possible to go. 



As already said, we must allow long ages for the recent sculpturing of the 

 island before we get back to the time when the building up of the limestones 

 was completed and they were pushed up above the water ; but to these come 

 those other vast ages while the limestones were being extracted from the sea- 

 water by the several living agents and being built up slowly in the sea ; farther 

 back again, before those long ages of building, came the long ages of the earlier 

 destruction, when the great folds of the clay formation were everywhere being 

 cut down to expose the upturned edges, those edges which were to be lowered 

 into the sea and to receive the limestones ; lastly, we go still farther back and 

 contemplate the long-continued building up in the sea, most likelv from vol- 

 canic products, of the numberless strata that make up our clay or blue-beach 

 formation. How vast a period must thus have elapsed from the deposition of 

 the oldest visible layer of our island's rocks to the present time, when we see 

 those rocks being destroyed once more to be added again to the materials ac- 

 cumulating in the bed of the ocean ! 



