MINERAL COAL. 331 



The areas of the "coal-measures" of the Carboniferous era, in 

 the United States, are as follows : 



1. A small area in Rhode Island, continued northward into Massa- 

 chusetts. 



2. A large area in Nova Scotia and New Brunswick, stretching east- 

 ward and westward from the head of the Bay of Fundy. 



These two areas are now separated ; but it is probable that they 

 were once united along the region, now submerged, of the Bay of 

 Fundy and Massachusetts Bay. 



3. The Alleghany Region, which commences at the north on the 

 southern borders of New York, and stretches south west ward across 

 Pennsylvania, West Virginia, and Tennessee to Alabama, and west- 

 ward over part of Eastern Ohio, Kentucky, Tennessee, and a small 

 portion of Mississippi. To the north, the Cincinnati " uplift," or 

 the Silurian area extending from Lake Erie over Cincinnati to Ten- 

 nessee, forms the western boundary. 



4. The Michigan coal area, an isolated area wholly confined within 

 the lower peninsula of Michigan. 



5. The Eastern Interior area, covering nearly two-thirds of Illinois, 

 and parts of Indiana and Kentucky. 



6. The Western Interior area, covering a large part of Missouri, 

 and extending north into Iowa, and South, with interruptions, through 

 Arkansas into Texas, and west into Kansas and Nebraska. 



The Illinois and Missouri areas are connected now only through the 

 underlying Subcarboniferous rocks of the age ; but it is probable that 

 formerly the coal fields stretched across the channel of the Missis- 

 sippi, and that the present separation is due to erosion along the 

 valley. Rocks of the Carboniferous period extend over large portions 

 of the Rocky Mountain area, but they are mostly limestones, and are 

 barren of coal. 



The extent of the coal -bearing area of these Carboniferous regions 

 is approximately as follows : 



Rhode Island area 500 square miles. 



Alleghany area 59,000 square miles. 



Michigan area 6,700 square miles. 



Illinois, Indiana, West Kentucky 47,000 square miles. 



Missouri, Iowa, Kansas, Arkansas, Texas 78,000 square miles. 

 Nova Scotia and New Brunswick 18,000 square miles. 



The whole area in the United States is over 190,000 square miles, 

 and in North America about 208,000. Of the 190,000 square miles, 

 perhaps 120,000 have workable beds of coal. 



Anthracite is the coal of Rhode Island, and of the areas in Central 

 Pennsylvania, from the Pottsville or Schuylkill coal field to the Lacka- 

 wanna field, while the coal of Pittsburg, and of all the great coal- 

 fields of the Interior basin, is bituminous, excepting a small area in 

 Arkansas. Anthracite belongs especially to regions of upturned 

 rocks, and bituminous coal to those where the beds are little disturbed. 

 In the area between the anthracite region of Central Pennsylvania 

 and the bituminous of Western, and farther south, the coal is semi- 

 bituminous, as in Broad Top, Pennsylvania, and the Cumberland coal 

 field in Western Maryland, the volatile matters yielded by it being 15 



