HOW OUR COAL WAS MADE 229 



work upon that thick, black, oozy marsh, full of the 

 fern fronds and the scales, the branches and the 

 tree trunks that had fallen into it. Then the marsh 

 was changed into a black, shiny mass of rock in 

 which was stored the carbon that the leaves and 

 trunks of those immense trees had breathed in from 

 the heavy air. 



Can you guess the name of this black rock? Yes, 

 it is coal. In the underground storehouse the car- 

 bon that was not needed by the growing world was 

 packed away and saved to be given back to the world 

 again m a form it did need. For the carbon that 

 would have poisoned us, had we breathed it in that 

 heavy atmosphere, could be used for giving warmth 

 when the world was getting cold. In such wonder- 

 ful ways does God provide for all His children. 



When the pressure upon the buried marsh turned 

 the black soil into rock, the clay and sand below the 

 swamp, and that with which the waves had covered 

 it, were changed into rock also. These rocks, too, 

 became a part of nature's book, for they were 

 changed into slate and sandstone and they have pre- 

 served for us the record of what grew in that ancient 

 marsh. In many a strange and beautiful way they 

 show us what sort of plants and trees those were 

 which made our coal. 



Underneath the black coal, standing upright in 

 the slate that had once been clay, are trunks of trees 

 all turned to stone, with long roots stretching through 

 the mass of rock. While above the coal, between it 

 and the layers of the slate, are the forms of delicate 

 little ferns, of large fronds and of the scale-covered 



