C.—GEOLOGY 69 
scattered outcrops of Lower Palzozoic formations around the Midlands in 
later foldings of the Carboniferous rocks. ‘There is no chessboard or other 
interlacing of the folds. ‘The folds are congruent, curving, clustered or 
‘divergent ; acute and often steeply pitching where there is great change 
of stratigraphical level, but ill-defined and widely separated where the 
troughs are broad. It is difficult to perceive how, in yielding under 
unilateral stress, sheets of new-made Coal Measures could have wrinkled 
in such forms. It seems more likely that, like blankets on the bed of 
-arestless sleeper, they have heaved and buckled in accommodating them- 
selves to the movements down below. It is recognised that in the con- 
temporaneous filling of each deepening syncline, as old folds tightened 
differences of rigidity between adjoining areas must have been perpetuated, 
and thus, whatever crustal thrust has later disturbed the underlying Lower 
Palzozoic platform, could not do other than exaggerate existing strains. 
Established lines of yielding have been from age to age rejuvenated, but 
the plotting of fold-lines has discovered no local bending structures in 
the Midland Coalfield Province, which can be determined as begun by 
late Carboniferous movements, or as having adopted a novel impressed 
Armorican or Hercynian trend. 
To the coalminer the unit of structure is the coalfield—a group of 
several down-folds forming a distorted trough or synclinorium. For the 
geologist arches are more conveniently described as individual structures, 
The complex ridge of Charnwood pitches down north-westward under 
the Trent Valley, beyond which, by Ashbourne, folds rise to culminate 
near Buxton. Northwards the Pennine anticlinal crest droops down 
some 2,000 ft. under Kinderscout. ‘Thence it continues almost on level 
course along the mid-Pennine ridge of Millstone Grit, and curves a little 
towards the east to Keighley. At intervals of a few miles the High Peak 
ridge throws off, most noticeably towards the east, trailing transverse 
folds, which spread fanwise across the Derbyshire Coalfield. ‘These trans- 
verse folds are sinuous in plan, and variable both in amplitude and pitch. 
Locally intensified, they bring up the limestone inliers of Crich and 
Ashover, and the cracked domes which were pricked for oil, successfully 
at Hardstoft, but unsuccessfully at Brimington, Renishaw, Ridgeway and 
Ironville. Never straight, their direction swings round in reversed ‘S’ 
bends almost through a quadrant. 'To the north in the moorland country 
the transverse undulations are less acute, their crest-lines swing first 
northwards, and then eastwards and a little southwards, as they lose 
themselves in the broad trough of the Yorkshire Coalfield. 
On the west side of the Pennine-Peak-Charnwood ridge-line the change 
of geological level is rapid. In Leicestershire the Thringston Fault puts 
Coal Measures against Pre-Cambrian, and with the two or three sharp 
infolds of minor coalfields west of Buxton, the High Peak adjoins the 
Cheshire Plain. This last great downfold, however, is not a simple 
structure. To it, as to a neck, the extensions of the folds between 
Charnwood and the Longmynd come to meet and join. The triangular 
form of the North Staffordshire Coalfield demonstrates the gape of the 
virgation within whose southward opening rise the ribs which are the 
Productive Coalfield of the Midland district. The plotting shows that 
