324 PALEOZOIC TIME — CARBONIFEROUS AGE. 



formation, 123 feet ; rests upon a sandstone, probably of the Mill- 

 stone grit epoch, which is 105 feet thick. 



4. The Texas, covering several of the northern and northwestern 

 counties. 



5. The Rhode Island, lying between Providence and Worcester 

 in Massachusetts, and opened at Cumberland north of Providence, 

 at Portsmouth 23 miles south, and also showing thin seams at 

 Newport and elsewhere ; in Massachusetts, outcropping at Mans- 

 field 15 miles northeast of Providence, at Wrentham 5 miles 

 from Mansfield, and at Worcester. Estimated area, 1000 square 

 miles. 



6. The New Brunswick, covering part of New Brunswick, Nova 

 Scotia, Prince Edward's Island, and Newfoundland. Estimated 

 area, 18,000 square miles. Whole thickness of the formation at the 

 Joggins, including the beds of the Millstone-grit epoch, 14,570 

 feet : the number of included coal beds is 76, some of them being 

 very thin, and the aggregate thickness 45 feet. (Logan.) These 

 coal beds are situated in a part of the Coal measures, 2819 feet 

 thick, near the middle of the series. At Pictou there are six beds 

 of coal, with an aggregate thickness of 80 feet. (Dawson.) 



The total number of square miles of all the productive coal fields 

 of the United States is 125,000. 



Besides the above, there is the Arctic Coal region, which has been 

 observed on Melville and Bathurst Islands, Banks Land, etc., and 

 the Rocky Mountains, both of which are yet unexplored. 



Limestones of the Carboniferous period — formerly supposed to be Subcarboni- 

 ferous — have a wide distribution over the summit and both the eastern and 

 western slopes of the mountains. This limestone has been observed at the 

 Black Hills in Dakota, and the Laramie Range ; about the head-waters of the 

 Missouri ; at the South Pass of the Rocky Mountains ; in the ranges south of 

 Pike's Peak, and east and west of Santa Fe, New Mexico ; in the great basin 

 of the Colorado ; and it probably underlies to a considerable extent the Meso- 

 zoic rocks of the Rocky Mountain slopes west of the Mississippi. 



II. Rocks. 



1. Kinds of rocks, and stratification. — The Coal measures include stra- 

 tified rocks of all kinds, — sandstones, conglomerates, shales, shaly 

 sandstones, limestones ; and the limestones are generally impure, 

 or magnesian. There is the same wide diversity that occurs in the 

 Devonian, with more numerous and rapid transitions than were 

 common in that age. Moreover, the rocks differ much in different 

 regions. 



The Coal beds are additional layers in the series, interstratified 



