Geology of Coalbrook Dale. 429 



stone is exhibited. From the care with which Mr. Anstice has had the 

 sections of the pits at Madeley taken, they afford the most correct information 

 of the number of strata, and of the total thickness of the coal-measures. The 

 details from which the following summaries have been deduced, were in part 

 supplied by that gentleman. 



Depth. No. of Strata. 

 Meadow Pits, Madeley .... 750 feet 134 



Hill's Lane ? 714 108 



The following are sections in other parts of the coal-field : — 



Depth. No. of Strata. 



Lightmoor 460 46 j The minuter subdivisions in these sections not 



Dawley 450 58 being generally given, as they are at Madeley, 



Malinslee 560 51 ! will account for the disproportion between the 



thickness and number of the strata ; and, in one 

 stratum, at one pit, may be included several of 

 an adjoining pit. 



Woombridge 540 70 



New Hadley 440 57 



Donnington Wood . . 560 60^ 



Of the two deepest pits in the coal-field, I could obtain no sections. At the 

 Woodhouse, near Priorslee, and at the Lodge Wood, pits have been sunk in 

 which the clod coal* is 300 yards deep. As the higher strata in these 

 works, and those of Madeley, are quite unproductive, and probably constitute 

 the uppermost carboniferous series in this district, we may assume that the 

 coal-measures have an average thickness of 1000 or 1100 feet, and consist, 

 at the utmost, of ninety distinct strataf. 



I endeavoured to obtain one or more shaft sections from every district in 

 the field I ; in many parts, however, no accounts have been kept, and I have 

 had to depend upon the statements of the ground-bailiffs. From long prac- 

 tice, the memory of these superintendents is generally tenacious ; but as 

 it is liable to error, I have affixed a note of interrogation to all such sec- 

 tions; and to those which have appeared to me as very doubtful, I have at- 

 tached two or more notes of interrogation : 1 have, however, taken every pos- 

 sible pains to ascertain the correctness of the accounts given to me. In most 

 of these sections, except those at Madeley and a few other works, the thin, bi- 

 tuminous shales in contact with the coal are included in the thickness of the 

 coal. At one pit, as already observed, several strata may be reckoned as one ; 



* The clod coal, which, from its regularity and persistence over the whole field, affords the 

 best geological horizon, is, upon an average, about 60 feet above the base of the carboniferous 

 series, (see Diagram, shaft sections, PI. XXXVII.) 



t The numerous thin local seams of coal and partings of clay laid down in the Madeley Pits 

 are not here taken into account. 



I See postea Appendix. 



3 r2 



