C.—GEOLOGY 71 
outcrop is really straight or continuous for many miles, but major fault- 
lines curve witha radius which is often greater than ten or even twenty miles. 
Leading faults, changing direction, give off tangential branch faults or 
receive tributaries which trail in at angles less than 45°. Transverse 
faults are usual across the troughs of pitching synclines. Where trans- 
verse and longitudinal faults cut the country into more or less quadrangular 
blocks, faults which are ending bend to meet the curve of the persistent 
fault. 
Large faults are generally associated with change of dip or change of 
strike of strata, and are therefore inconstant in their throw. Large 
faults frequently occur en echelon in the middle limbs or sides of troughs, 
where their direction makes a small angle with both the strike of the 
measures and the pitch axis of the fold. Mostly faults tend to converge 
towards a rise of pitch. ‘Transverse faults sometimes displace the crests 
of anticlines, but are of greater importance as they reduce the effect of 
pitch along the synclines. Most transverse faults bend and lose their 
throw as they approach the steeper middle limbs of folds, and change the 
curvature of their direction as they pass from anticline to syncline. 
Certain groups of complex or paired trough fractures sweep in 
discontinuous arcuate curves across the Midland Coalfield Province on 
a radius as great as fifty or sixty miles. These are not obviously related 
either to the trend of noticed folds or to the longitudinal or transverse fault 
breaks, with some of which they join. Of them the most extensive system 
follows a rude semicircle through the North Lancashire and East Pennine 
Coalfields from Accrington, by Todmorden to Huddersfield and Sheffield, 
and across Derbyshire to the Dukeries. If it is continuous with the fault 
belt which from Blackburn extends to Wigan and St. Helens, it may 
encircle the Cheshire Basin. 
Other fault groups which bend round the High Peak of Derbyshire 
also cross the Pennines. These carry on through the Derbyshire and 
Nottinghamshire Coalfield, and may encircle the platform of Charnwood 
Forest. The most northerly of this group traverses the Pennines from 
Rochdale to the Calder Valley, and intercrosses with the Todmorden- 
Sheffield disturbance in the Rishworth Moors. A more southerly group 
close to the limestone boundary at Castleton passing by Holmesfield and 
Chesterfield to the south of Mansfield, crosses and recrosses the reversed 
*$° bend of the Brimington anticlinal axis. 
In Flint and Denbighshire also, arcuate groups of fractures likewise 
slice across the horseshoe fold axes. These are circumferential to the 
Silurian buttress of Snowdonia. Where, in the Trent Valley, Trias is 
banked against the southern ending of the Pennines, broadly arcuate 
east-west fractures cut directly across the Pennine Carboniferous folds. 
Appreciation or description of coalfield fault pattern is difficult except 
by diagram, but regional trends change gradually, and within the Midland 
Coalfield Province the only apparent discontinuities are gaps or obscurities 
due to lack of information. Drift obscures the fault outcrops in the Trias 
_ country, and Carboniferous, deep bedded under Trias, reveals its structure 
only as the coal is worked. 
The criss-cross fault arrangement of the Yorkshire Coalfield has been 
