190 THE WORLD. 



8. THE CARBONIFEROUS, OR COAL SYSTEM, which is formed of 

 sandstones, grits, shales, layers of ironstone, and clay ; with 

 immense beds of coal; fresh water limestone sparingly, and ma- 

 rine limestone abundantly. This system is characterized by in- 

 numerable remains of land and aquatic plants, of a tropical char- 

 acter, and belonging to extinct species and genera, with fishes, 

 reptiles, and insects. The series includes the coal measures, 

 which are sandstone, and shale, with numerous layers of coal, 

 containing land plants in profusion. Limestones, with fresh water 

 and marine shells, Millstone grit, which consists of sandstone 

 and shale, with thin seams of coal, and quartose conglomerates 

 sometimes used for millstones. The carboniferous or mountain 

 limestone, consisting of limestone and flagstone, abounding in 

 crinoidea, and marine shells, yielding several varieties of black, 

 blueish grey, and variegated marbles. The coal bearing strata of 

 this country differ some from the European. The seams of coal 

 appear however, even in Europe, to be very unequally distributed; 

 although the great coal formation belongs in the order where we 

 have placed it, yet seams of anthracite coal are found in almost 

 every rock from the lias, to the upper metamorphic rocks, show- 

 ing that the coal beds have occurred at very unequal intervals, 

 hence their formation may be of any date between the new and 

 the old red sandstone. 



9. THE DEVONIAN, OR OLD RED SANDSTONE SYSTEM. This 

 name is derived from the English locality, where it is most large- 

 ly developed, viz : Devonshire. It is a marine deposit, chiefly 

 remarkable for its extraordinary forms of fossil fish. This sys- 

 tem is composed of various strata, flagstones, conglomerates, 

 quartose grits, sandstones, marls, and limestones ; the prevailing 

 color of all these is a dark red. But few fossils are found in the 

 sandstone and conglomerates, but in the marls, and concretionary 

 limestones, sometimes called corn-stones, peculiar genera of fish, 

 and many species of marine shells are found. This system lies 

 immediately below the mountain limestone. The sandstones are 

 in various stages of induration, and when slaty are employed fot 

 roofing. The red color is derived from peroxide of iron. The 

 formation of these rocks, has manifost.lv resulted from the \va*te 



