Great Coal-Jield of Shropshire. 1 99 



sixteen feet at Old-park, and eighteen feet at Ketley. That the V'lger 

 coal, with its superincumbent clay, occupies a thickness of about twelve 

 feet at Madeley, is diminished to three feet at Lightmoor, and is 

 entirely wanting in all the collieries which lie to the north of the 

 latter. That a bed of clay, usually known by the name of the upper 

 chinches^ bears a thickness of from fifteen to twenty-six feet in all 

 the above mentioned collieries, except that of Ketley, where it is en- 

 tirely wanting. 



The rock upon which the coal formation rests, is either die-earth 

 or limestone. 



The die-earthy or dead earth as it is also called, is a name given 

 by the miners to this bed as indicative of the fact that from hence 

 downwards all the coal strata die or cease. Its colour is greyish ; and 

 it consists of fine sand, of particles of limestone, and of clay, mixed 

 together in very various proportions ; it is often also micaceous. It 

 has sometimes a strong tendency to a slaty structure and a stratified 

 arrangement, with which also the direction of the spangles of mica 

 that it contains for the most part corresponds. It contains a few 

 bivalves, chiefly of the genus cardium, and the entomolithus para- 

 doxus, or Dudley fossil. The thickness of this bed is very various, 

 from a few feet to an hundred yards ; it incloses fragments of lime- 

 stone, and is interposed between the limestone and the coal-forma- 

 tion without possessing the dip or direction of either one or the 

 other. 



In order to obtain a clear idea of the I'lmestone-fonnation^ it will 

 ^e necessary to commence our observations at the south-eastern ex- 

 tremity of the district here described, where we shall find two pa- 

 rallel ranges of limestone running nearly N.E, and S.W. Of these 

 ranges, that which lies the most easterly will first engage our atten- 



