EARTH 



days, are slowly and surely being worn away 

 and made low, while the valleys will gradually 

 be filled up with the tiny grains that were once 

 on the hill-side. 



How the land and sea and mountain-ranges 

 were first made is a very difficult question, and 

 one that I do not think we could answer from 

 our own observation. To understand even a 

 little about it we should have to talk with the 

 men who have studied such questions, the geo- 

 logists, as they are called, and read the books 

 they have written on the subject. They would 

 tell us that banks of sand and soil brought down 

 by the rivers, many thousand years ago, have 

 been left at the bottom of valleys and lakes, 

 and pressed closely together, layer upon layer, 

 until once more they hardened into rock. In 

 the same way, as the little particles of sand or 

 the tiny remains of sea-animals and plants fall 

 slowly down through the waters of the ocean, 

 a fine covering of mud and ooze is formed at 

 the bottom of the sea. Then the surface of the 

 earth has gradually moved up and down, until 

 in places the bottoms of sea and lake have risen 

 up to become dry land, and the land itself, in 

 its turn, sunk under the water. Sometimes 

 too, in far off ages, the face of the earth seems 

 to have crumpled up, much as we might crumple 

 up a copy-book or door-mat if we were to push 

 the two ends towards each other, and these 

 movements have made the great mountain- 



