04 
TRANSITION SERIES. 
and geological changes which then prevailed 
secondly, as affecting, in no small degree, the 
actual condition of the human race. 
The strata in which these vegetable remains 
have been collected together in such vast abun- 
dance have been justly designated by the name 
of the carboniferous order, or great coal forma- 
tion. (See Conybeare and Phillips’ Geology of 
England and Wales, book hi.) It is in this 
formation chiefly, that the remains of plants 
of a former w^orld have been preserved and con- 
verted into beds of mineral coal ; having been 
transported to the bottom of former seas and 
estuaries, or lakes, and buried in beds of sand 
and mud, which have since been changed into 
sandstone and shale. (See PI. 1, sec. 14.)'t' 
*■ The nature of these vegetables, and their relations to ex- 
isting species, will be considered in a future chapter. 
t The most characteristic type that exists in this country of the 
general condition and circumstances of tbe strata composing the 
great carboniferous order, is found in the north of England, h 
appears from Mr. Forster’s section of the strata from Newcastle- 
upon-Tyne to Cross Fell, in Cumberland, that their united thick- 
ness along this line exceeds 4,000 feet. This enormous mass is 
composed of alternating beds of shale or indurated clay, sand' 
stone, limestone, and coal; the coal is most abundant in the 
upper part of the series, near Newcastle and Durham, and th® 
limestone predominates towards the lower part; the individual 
strata enumerated by Forster are thirty-two beds of coal, sixty' 
two of sandstone, seventeen of limestone, one intruding bed 
trap, and one hundred and twenty-eight beds of shale and clay- 
The animal remains hitherto noticed in the limestone beds at® 
almost exclusively marine ; hence we infer that these strata w'C® 
