ON COAL. 



129 



seams are generally near the middle of tkis series ; as if tlie conditions 

 necessary for the formation of coal had gradually come into existence 

 and as gradually disappeared ; that there were two poles and an 

 equator belonging to this time-world — a morn, noon^ and evening to 

 this geological day. 



We have spoken thus far only of the thickness of coal strata and of 

 coal seams ; but it is impossible to form a correct idea of the amount 

 of matter contained in these strata or in these seams without taking 

 into account also their horizontal extent. Coal is very widely dis- 

 tributed over the world,, although some countries are more favored 

 than others. England, France, Spain, Portugal, Belgium, Sweden, 

 Poland, and Russia have their beds of coal. It is also found abun- 

 dantly in Asia, Africa, and South America ; but no where is the coal 

 formation more extensively displayed than in the United States, and 

 no where are its beds of greater thickness, more convenient for work- 

 ing, or of more valuable quality. There are within the limits of the 

 United States no less than four coal fields of enormous dimensions. 

 One of these, the Appalachian coal field, commences on the north, in 

 Pennsylvania and Ohio, sweeping south through western Virginia 



Ur.S. (j£ A-merica. 



CoalArea 

 103500 S^.Miles 



Brit . Amer. '; Gr. Brit . 



18000 i 11860 



Sy. 771 \ S(f.Tn 



Spaia 



3±08 



a ° 



France Belgiom 



1719 5L8 



Sff-Tih Sq,.Tn< 



and eastern Kentucky, Tennessee, extends even into Alabama. Its 

 area is estimated at about 60,000 square miles. A second occupies 

 the greater portion of Illinois and Indiana ; in extent almost equal to 



* Recent estimates by Marcou and by H. D. Rodgers make the coal area of the United 

 States near 200,000 square miles. 



9 s 



