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changes which they have produced in the relative position of the 

 beds of coal ; and he refers to the nriemoirs of Mr. Murchison for an 

 account of the formations on which the coal-measures repose. 



The coal-field is traversed a little north of the Severn by a ridge 

 called " the limestone fault," which has a nearly east and west 

 direction, and by which the field is divided into two unequal parts. 

 That portion which lies to the north of the line of disturbance is 

 intersected by four faults trending from nearly north-east to south- 

 west, but without preserving a strictly parallel direction. They 

 are called the Boundary, Ketley, Main or Leightmore, and Kanley 

 faults. 



The Boundary fault, which ranges from Lilleshall Hill to Arcol 

 Hill, the author does not consider to be a true fault, but only to 

 mark the line beyond which, to the north-west, no workings are 

 conducted. Along the line, the dip of the beds suddenly increases 

 from 2° north-west to 13°, and afterwards to 30°. These changes 

 have been ascertained by sinking shafts ; and by means of workings 

 conducted from them it has been proved that the beds of coal, after 

 preserving the last dip for a short distance, suddenly rise towards 

 the surface, in an opposite direction, at an angle of 30°. The out- 

 crop of the measures is concealed by the overlying red marl, but the 

 author is of opinion that the strata may terminate against an under- 

 ground ridge of limestone or against one of the rocks composing 

 the Wrekin. Between New Hadley and the Glass House, in the 

 direction of the synclinal line, the " clod coal" is 180 yards deep. 



The Ketley fault is situated to the south-east of the Boundary 

 fault. It is perpendicular, and was traced by the author from the 

 Glass House to the Red Lake, but he states from the informa- 

 tion which he received, that it extends to the base of Steeraways 

 Hill. At the Glass House, and in other parts of its range, the walls 

 of the disjointed measures are in contact, but they are occasionally 

 30 yards asunder, and the space is filled with the detritus of the ad- 

 joining strata. The greatest difference of level is about 140 yards. 



The Main or Leightmore fault was traced from Sneeds Hill En- 

 gine to Coalbrookdale. It inclines towards the south-east, and 

 its breadth is about 60 yards, the intervening space being filled with 

 fragments of the coal-measures. The greatest difference of level on 

 the opposite sides of the fault is stated to be 260 yards. 



The Ranley fault ranges parallel to the Main. The author did 

 not discover its north-eastern extremity, but he traced it from Dark 

 Lane towards Sturchley; he states, however, from the information of 

 the colliers, that it extends to the limestone fault. The breadth is 10 

 yards, and the inclination towards the south-east. The greatest dif- 

 erence of level is 50 yards. 



Besides these four principal faults of the northern portion of the 

 coal-field, the author notices several minor ones which have a di- 

 rection generally at right angles to the principal faults, and which 

 appear to have had considerable influence in producing the difference 

 in the level of the strata. 



The ridge called the limestone fault, which divides the coal-field 



