PALEOZOIC TIME — CAEBOiStlC. 657 



Upper Productive, 200'; Upper Barren, 500', but much reduced from the original thickness 

 "by denudation ; the total number of coal-beds is 13 ; the mean thickness of the lower 7 is 

 4|'; of the upper 6, 4'. Bed No. 1, called the Brier Hill, Massillon, or Jackson coal, is 

 3' to 6' thick, and is supposed to be No. A of the Pittsburg section ; No. 6, the Upper 

 Freeport, 3' to 12' thick ; No. 8, 4' to 8' thick, the Pittsburg coal-bed, at the top of the 

 Lower Barren Measures ; and No. 11, 1|' to 4' thick, the Waynesburg coal-bed (Newberry). 



In Indiana, the Coal-measures cover an area of about 7000 square miles over the 

 western part of the state, are 800' to 1000' thick, and include 10 coal-beds varying from 

 1' to 11' in thickness (CoUett). 



In Illinois, the total thickness is 600' to 1000', and the number of workable coal-beds 

 6, and of other thin seams, 6. The thickness of the former is nearly 20' (Worthen). 

 Near Morris, and elsewhere, in northeastern Illinois, there is a single bed of coal with clay 

 above and below. Pour miles to the southeast of Morris, sandy shales of the Coal-measures 

 ■contain concretions which have made the place famous because of the many kinds of 

 Ferns, Insects, Spiders, Myriapods, rare Crustaceans, and even Amphibians, which have 

 been found in the concretions — the specimens having been in many cases the nuclei. 

 No marine fauna has been found in them. 



In southwestern Kentucky, the Coal-measures north of Pine Mountain are 1650' thick, 

 and contain 9 workable beds of coal ; and farther east they are still thicker. 



The Coal-measures spread northwestward over southwestern Iowa, where they have a 

 maximum thickness of 600', and a thickness of coal-beds of about 8', as in Illinois. The 

 Coal-measures extend northward beyond the limits of the upper beds of the Subcarbonif- 

 erous limestone. At Davenport, on the Mississippi, a boring found a thickness of 30', and 

 the beds resting on the Devonian Corniferous limestone. 



In Arkansas, the area of the Coal-measures is about 1000 square miles, and the mean 

 thickness of the coal-beds is estimated at 3'. 



The isolated coal area of Michigan covers about 6700 square miles, and the beds have 

 a thickness of 300' or less. At East Saginaw, this 300' includes the underlying Parma 

 white sandstone 105', and the overlying Woodville brown sandstone 79 feet ; and in the 

 intermediate shales and sandstone there is one bed of coal 3' to 4' thick (Winchell). 



In Alabama, the Coal-measures cover 5500 square miles. There are 3 areas, — the 

 Warrior, the Cahaba, and the Coosa. The first contains nine tenths of the whole area. 

 The thickness near Tuscaloosa, where the beds disappear beneath more recent formations, 

 is about 3000'. The number of coal seams is about 35, of which 15 are over 2|' thick, and 

 6, of 4' and over. The beds become thinner to the northwest. The lowest of the coal-beds 

 are those in the Pottsville conglomerate. 



The Khode Island Carboniferous covers the most of the southern part of the state, and 

 extends northward, through Providence, to the northern border : there it passes into 

 Norfolk County, Mass., and thence eastward, through Bristol County, to Plymouth 

 County. The exact limits, east, west, and north, have not been made out, the stratifica- 

 tion of the rocks being much obscured by displacements or flexures and metamorphism. 

 There are conglomerates and slates which are supposed by Hitchcock and Jackson to be a 

 part of the formation. The quartzose conglomerate outcrops at Newport and elsewhere, 

 and forms a bold feature in the landscape at " Purgatory," 2i miles east of Newport, and 

 at the "Hanging Rocks." The stones vary in size from an inch to a foot or more. 

 Associated with the slate there are beds of limestone. 



The principal points where coal outcrops are near Providence, Cranston, Bristol, 

 Portsmouth, Valley Falls, Cumberland, and Newport (a thin bed outcropping on the coast) , 

 in Rhode Island ; and in Raynham, Wrentham, Foxboro, and Mansfield, in Massachu- 

 setts. The beds are much broken and very irregular in thickness, owing to the upturning 

 and flexures the formation has experienced, and the coal is an exceedingly hard anthra- 

 cite, because of the metamorphism, and to some extent is graphitic. Still, the slates often 

 contain fossil plants, part of which are identical in species with those of Pennsylvania. 



DANA'S MANUAL — 42 



