B. Jones — Denudation of Coalhrook-dale. 201 



One of the principal features pointed out by Sir E. Murcliison, 

 Bart./ and J. Prestwich, Esq., F.E.S.,^ is the want of persistency 

 in the strata and Coal-seams. In the references which I am 

 about to make to the works of authors on this Coal-field, I am 

 desirous of saying that I do not wish to recall opinions expressed 

 some thirty or forty years since, with the object of showing that 

 they were incorrect, but merely to lay before the reader the state 

 of knowledge upon the subject previous to the true explanation of 

 the nature of the Symon fault made by Mr. Marcus Scott,^ and by 

 which alone I am able to offer the present interpretation of those 

 difficulties which I have referred to. 



When Mr. Prestwich gave his paper to the world in 1836, the 

 true nature of the Symon fault had not been explained. It was to 

 him, as to many others since he wrote, a very great puzzle, but now 

 its explanation serves not only to elucidate the phenomena along the 

 eastern boundary of the Coal-field, but also to account for the great 

 difference between the strata of the northern and southern portions. 

 It will be shown that the southern portion has been largely denuded, 

 and subsequently laid over with Coal-measures of a younger age, and 

 consequently that the Carboniferous deposits are not uniform or 

 persistent. Thus the observation, " that 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" in this Coal-field, is not 

 supported. The details from which the following summaries have 

 been deduced were in part supplied by that gentleman : — 



Depth. No. of strata. 



Madeley Meadow Pits 750 feet. 134* 



Hills-lane 714 „ 108 



Now I would observe that the first of the older series of Coal-seams 

 in the Meadow Pits is the Eider Coal (so called), which, however, is 

 the same as the Double Coal of the other portions of the field ; and 

 I consider No. 67 of that section, described as "light rock full of 

 pebbles, green, blue, and red hard," to be the point of division be- 

 tween the upper and lower, otherwise younger and older, series, or 

 the line of abrasion of the older Coal-measures. If I am right, then 

 there are only 65 strata which belong to the older Coal-measures 

 in that section. The Hills-lane section shows no Big Flint Coal ; 

 and I consider No. 76, called " Bottom Coal Flint," is the first re- 

 cognizable older stratum, and, consequently, there are only in that 

 section 33 strata belonging to the lower Coal-measures. So that 

 Madeley is not a locality in which the Coal-measures of the Coal- 

 brook-dale Coal-field are at all well represented. We are given a 



^ MurcMson's Silurian System, 1839, 4to. p. 86, etc. 



2 Prestwich, Trans. Geol. Sec. London, 1840, 2nd ser. vol. v. p. 413. 



3 Quart. Journ. Geol. Society, 1861, vol. xvii. p. 457. 



* Prestwich on the Geology of Coalbrook-dale, Geol. Trans., vol. v. 



