CARBOX 



63 



cite coal generally consists of about 95% carbon while 

 bituminous coal contains 80% or less of carbon. 



Copyright by Underwood d- Underwood, N. Y. 

 Fig. 27. Mining anthracite coal three miles underground. 



Coal is wood that has undergone great changes dur- 

 ing past centuries. The harder the coal the longer 

 this change has been taking place. During a period 

 of the earth's history known as the Carboniferous 

 Age, the earth was covered with a luxurious growth 



