﻿Vol. 6 1.] IIST THE NOKTEE-STAFFOEDSHIRE COAL-MEASURES. 513 



Doubtful Marine Horizons in the Pottery Coalfield. 



In addition to the foregoing list of marine horizons, two others 

 have been recorded from the Pottery Coalfield, the existence of 

 which is extremely doubtful. They are :-— 



1. A few feet above the Grin Mine or Golden Twist. 



2. About the Ten-Feet Coal. 



(1) The horizon above the Gin Mine was recorded by William 

 Molyneux, 1 and by Mr. John Ward in his valuable monograph of 

 the North -Staffordshire Coalfields, 2 and from the latter it has spread 

 over a large circle of publications. In an earlier paper, written 

 nearer the time of the discovery of the band, Mr. Ward describes a 

 similar horizon lying c a short distance below the Gin Mine.' 3 

 This position agrees with the marine band described hereinbefore 

 (pp. 500-503). After careful discussion with Mr. Ward, I gather 

 that he is inclined to think that the word i above ' should have been 

 printed ' below.' At any rate, I have watched sinkings and 

 * crut '-driving without finding any trace of a marine bed above 

 the Gin Mine in the position described, which I therefore consider 

 erroneous. 



(2) The marine horizon about the Ten-Peet Coal is cited by 

 Prof. Hull, in his ' Coalfields of Great Britain ' 3rd ed. (1873) p. 178, 

 and in a paper read before this Society, Quart. Journ. Geol. Soc. 

 vol. xxxiii (1877) p. 628. I have taken every opportunity of 

 verifying the position of this band, but without success; and I con- 

 clude that the specimens were probably collected from the spoil- 

 heap of ' Lord Granville's colliery at Hanley,' and that the horizon 

 was not examined in situ. This view *is supported by an examina- 

 tion of the fossil -list from the horizon, which embodies a mixture 

 of freshwater and marine mollusca ; and such a commingling is 

 contrary to my experience of the occurrence of these mollusca 

 in all the other marine horizons with which I am acquainted. 

 At the same time, such a mixture of forms is precisely what 

 may be obtained from any colliery spoil-heap, which consists of the 

 debris brought from all the levels that, for the time being, are in 

 course of excavation. In this way, fossils from many horizons are 

 tipped together. I consider, therefore, that the marine shells have 

 come from some other horizon than that of the Ten-Peet Coal. 



IV. Explanation of the Map (PI. XXXIY). 



The outline-map (facing p. 514) shows the railway and canal- 

 system of North Staffordshire, with its chief towns. The position 

 of the collieries where the marine horizons have been traced is 

 also shown by numbered circles. 



1 Rep. Brit. Assoc. 1865 (Birmingham) p. 50. 



2 Trans. N. Staffs. Inst. Min. & Mech. Eng. vol. x (1890) p. 43. 



3 N. Staffs. Nat. R-C. : Addresses, etc. 1875, p. 192. 



Q. J. G. S. No. 243. 2 o 



