COAL. 193 



In various parts of the United States coal is 

 found abundantly, particularly in Pennsylvania. 



Coal and wood, though so different in their ap- 

 pearance, are much of the same nature. Coal-fields 

 are indeed the remains of vast forests, which have 

 at some distant period been buried under the sur- 

 face of the earth, and in the course of time changed 

 into this mineral. When we examine pieces of 

 coal, procured from some of our mines, the shapes 

 of many kinds of plants can be discovered in them. 

 Some of these impressions are very beautiful, and 

 so perfect that the particular plant can be easily 

 named. 



Coals are found lying in beds, or strata, and 

 always with strata of certain other mineral bodies. 

 By boring some little distance into the earth, we 

 soon find out whether there are any in that par- 

 ticular situation, for if we bore through one of these 

 bodies, it is quite certain that coal is below. 



This mineral is called combustible, which signi- 

 fies capable of supporting flame, that is, of being 

 made into fires. Besides being the food of manu- 

 factures and commerce, vast quantities are used as 

 fuel for domestic purposes, and contribute greatly 

 to our comfort. In London nearly two million 

 chaldrons are annually consumed, and in all Eng- 

 land upwards of fifteen millions. This amazing 

 consumption we might suppose would exhaust the 

 mines. Of this, however, there is no likelihood, 

 as it has been calculated that there is a supply for 

 four thousand years ; besides which there are 

 R 



