204 



THE WONDERS OF GEOLOGY. Lect. III. 



included all the deposits that intervene between the Triassic above, 

 and the Carboniferous systems below ; and these contain but one type 

 of animal and vegetable life. Remains of reptiles occur, and are the 

 most ancient, or earliest, of this class of animals. 



7. THE CARBONIFEROUS FORMATION. Sandstones, grits, 



shales, clays, and layers of ironstone, alternating with 

 beds of coal, form the upper series ; — limestone and flag- 

 stone, with layers and nodules of chert, abounding in 

 marine shells, crinoidea, and corals, constitute the lower 

 division of this extensive group of deposits ; the total 

 thickness of which is many thousand feet. The coal strata 

 are remarkable for the abundance and peculiarity of the 

 terrestrial trees and plants, of which they are almost wholly 

 constituted ; remains of insects, fishes, and crustaceans of 

 an extinct family have been found in this formation. 



Observations. — These strata, so interesting to the botanist from 

 the richness and peculiarity of their fossil flora, and to mankind in 

 general for the inexhaustible supply of fuel which they yield, appear 

 for the most part to have been deposited in salt water ; for the beds of 

 coal are generally associated with marine shells, corals, &c. ; and there 

 are only a few local intercalations of layers of fresh water shells. The 

 flora of the coal is the most striking feature of this system of deposits. 



8. the devonian ( Old Red) formation. — An as- 

 semblage of quartzose grits, sandstones, marls, and con- 

 glomerates, largely charged with peroxide of iron, which 

 imparts to the whole a dull red colour ; with beds of 

 coralline marble, and laminated micaceous sandstones ; 

 this formation was formerly, from its colour, denominated 

 the Old Red sandstone. Shells, corals, fishes, crustaceans, 

 and cephalopoda, of peculiar species and genera, are the 

 prevailing and characteristic organic remains. 



Observations. — The ierm Devonian, which has been substituted for 

 that of Old Red Sandstone, as being more precise, is derived from 

 the geographical development of this group of rocks in Devonshire, 

 England. The red conglomerates, which constitute a well marked 

 Hthological character, consist of water- worn fragments of slate with 



