210 THE EARTH MADE READY FOR MAN 



empty shells were dropping slowly to the bottom of 

 the sea and accumulating there in thick masses. 



During this time, too, the land was gradually rising 

 out of the ocean, and the ocean was becoming less 

 vast. You will remember that not all of the rain- 

 drops that rose to the clouds in the form of vapor got 

 back to the sea again. They gave themselves up to 

 becoming the beautiful minerals. There were still 

 other drops that never even started up into the 

 clouds to begin that long journey, but sank into the 

 gravel and the sand and the clay which the rivers had 

 brought with them to the ocean and, combining with 

 these, helped to make new rocks. 



That sounds odd, does it not? Who would think 

 that the pieces of rock, the pebbles, the sand and the 

 clay that the rain water in the brooks and rivers had 

 been so patiently wearing away from the earth's 

 crust would ever be used for making new rock? Yet 

 you know that the leaves that drop off the trees are 

 turned into soil to make other trees grow. Does it 

 seem very much stranger that the worn pieces of 

 rock should be used to make new ones? 



Those pebbles which the rivers had been bringing 

 down to the ocean had been accumulating upon the 

 ancient sea beach for countless years. The sand and 

 the clay, also, had been accumulating there in such 

 thick masses that the layers upon the top pressed 

 very heavily upon those below. The pressure was so 

 gi'eat that the pebbles and the sand and the clay, 

 saturated as they were with the water of the ocean, 

 became gradually compressed into masses of solid 

 rock. 



