A CHAPTER IN THE PHYSICAL GEOGRAPHY OF THE PAST. 61 
Both in the Warwickshire and in the South Staffordshire Coal- 
fields we find this splitting up of the Coal Seams even more 
marked than it is in our district, and the splitting up in both cases 
takes place, as in our Ashby Coalfield, fowards the north. In the 
South Staffordshire district, in the neighbourhood of Dudley, the 
to yard Coal, as it is called, is an undivided seam 30 feet thick ; 
but when traced northwards within a distance of a few miles it 
divides into zzze distinct seams, separated by an aggregate thick- 
ness of 420 feet of sandstone. The combined thickness of these 
nine seams of coal is only a little short of the original thickness 
of the undivided seam, so that besides having here a good 
example of horizontally progressive and intermittent subsidence, 
we have an indication of the extreme slowness with which the 
peat beds must have increased in thickness. The time taken to 
accumulate 420 feet of sedimentary strata was only sufficient to 
add at the outside a foot or two to the thickness of the coal seam. 
Thus we see all the evidence is in favour of the comparative 
stability of the land areas in Carboniferous times, and the 
gradual bending down of the floor upon which the sediment was 
deposited. 
I have now given you a condensed account of the leading facts 
connected with the laying down of the materials forming the 
Carboniferous Rocks of this part of Europe, and have shown you 
how the record of the conditions prevailing during their deposition 
is written in indelible characters in the rocks themselves. 
My sketch would, however, be incomplete if it did not include 
some reference to the agencies which have upheaved these once 
horizontal strata, and have brought them into the elevated position 
which they now occupy in the hill country of Northern England. 
We have already seen how, in the Pennine Range of hills, the 
rocks composing them are now arranged in a series of folds or 
corrugations. With a difference in degree only we always find 
this tendency to ridge and furrow arrangement in all strata which 
have been in any way disturbed, but it attains a maximum of 
development in mountainous districts, where the disturbing forces 
have been great; the folds, in such cases, assuming great height, 
