306 English Formations. 



shales and sandstones bearing coals. In fact, viewed as 

 a whole, the Carboniferous series consists only of one 

 great formation, possessing different lithological charac- 

 ters in different areas, these having been ruled by cir- 

 cumstances dependent on whether the strata were 

 formed in deep, clear, open seas, or near land ; or actually, 

 as in the case of the vegetable matter that forms the 

 coals, on the land itself. 



The English Carboniferous rocks differ from the 

 Scottish beds in this, that in general they have not 

 been mixed with igneous matter, except in North- 

 umberland and Derbyshire, where, in the last-named 

 county, the Carboniferous Limestone is interbedded with 

 ashes and lava, locally in Derbyshire called 'toad- 

 stones.' In South Staffordshire, Colebrook Dale, the 

 Clee Hills, and Warwickshire, there is a little basalt and 

 greenstone, which may possibly be of Permian age, 

 intruded into, and perhaps also partly overflowing, the 

 Carboniferous rocks in Permian times ; but in Glamor- 

 ganshire, Monmouthshire, North Staffordshire, Lan- 

 cashire, and Yorkshire, where the Coal-measures are 

 thickest, no igneous rock of any kind occurs. There 

 and elsewhere in England the Coal-measures as usual 

 consist of alternations of sandstone, shale, coal, and 

 ironstone. 



Next in the series come the Permian rocks (2, 3, 4, 

 fig. 30, p. 141), which, however, rarely occupy so great 

 a space in England, as materially to affect the larger 

 features of the scenery of the country. They form a 

 narrow and marked strip on the east of the Coal- 

 measures from Northumberland to Nottinghamshire, 

 where they chiefly consist of a long, low, flat-topped 

 terrace of Magnesian limestone (see Map), interstratified 



