CARBONIFEROUS PERIOD. 



323 



into many distinct patches ; and in the western part commences 

 the great bituminous coal field which spreads into Ohio and stretches 

 on south to Alabama. 



2. The Illinois and Missouri, covering a very considerable part of 

 Illinois, part of Indiana and Kentucky, and, west of the Missis- 

 sippi, portions of Iowa, Missouri, Kansas, and Arkansas. Esti- 

 mated area. 60,000 square miles. Whole thickness of the formation, 

 in Missouri, 600 to 1000 feet ; in western Kentucky, nearly 3300 feet, 

 — with about 70 feet for the aggregate thickness of the coal beds. 



t 



3. The Michigan, situated about the centre of the peninsula. 

 Estimated area, about 5000 square miles. Whole thickness of the 



