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. 



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

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



