Mr. Winch on the Geology of the Banks oj the Tkveed. 89 



As investigation advances, the lines of demarcation between 

 different formations seem to vanish, and doubts are left upon 

 the mind even whether distinct epochs have at any period in- 

 tervened beween the commencement and termination of the 

 consolidation of secondary strata. The mineralogical charac- 

 ters of rocks are now acknowledged to be no satisfactory evi- 

 dence of geological position; for by hand specimens, who can 

 point out the difference between the red sandstones, associated 

 with coal and encrinal limestone at Berwick, or with mag- 

 nesian limestone in the county of Durham? If the mode of 

 concretion is called to our aid, we find the oolitic form is as- 

 sumed, not only by the limestone usually denominated oolite, 

 but by the magnesian limestone at Hartlepool (Geological 

 Transactions, vol. iv. p. 7), and by the encrinal limestone at 

 Warcop in Westmoreland, as noticed by Mr. Fryer many 

 years since. Dolomite is interstratified with the carboniferous 

 or encrinal limestone in Derbyshire, as is chert in the lead 

 measures at Arkengarthdale in Yorkshire (Geol. Trans, vol. iv. 

 p. 63) ; but neither of these remarkable strata occurs in the 

 lead-mine district of Durham or Northumberland, though 

 a part of the same chain of hills ; nor can the identity of 

 millstone grit be here depended upon as in Derbyshire, for 

 one bed at least of this apparently well-defined rock, is asso- 

 ciated with coal measures at Hauxley, Widdrington, Ulgham, 



depth in that situation ; but at Thornton. Shoreswood, Gatherick, and 

 some adjoining places in the western part cf the district, it is worked under 

 the name of the Main Coal. Its thickness is from five to five and a half 

 feet, and its quality is not good, the bed being traversed by thin bands of 

 stone. 



6th. The Three-quarter Coal lies at variable distances below the Cancer 

 Coal, being in some places found at twelve, and at others twenty-two 

 fathoms deeper than that seam. Its usual thickness is two feet eight inches, 

 including a band of stone often inches; its quality is inferior to the better 

 coals of the district. 



7th. The Cowper Eye Seam is generally met with about four fathoms 

 below the Three-quarter Coal; it varies in thickness from two to three 

 feet of saleable coal, having a stone band in its middle, unequal in thick- 

 ness, but in some situations exceeding two feet. This seam is chiefly 

 worked in the western part of the district, as at Murton, Thornton, 

 Shoreswood, Felkington, Etal, Gatherick, Greenowalls, and their vicinity. 

 In quality, it is considered equal to No. 3, Scremerstone Main Coal. 



No. 8. The Western Coal Seam appears to me to be the lowest worked 

 in the district. It has been sunk to at Shoreswood, and there found at 

 about fourteen fathoms below the Cowper Eye Seam ; but the quality being 

 indifferent, it was not thought worth working. At Etal there is a mine 

 carried on in it, though even there the coal is of inferior quality. 



From the gradual rise of the strata to the westward, the first four seams 

 mentioned in the section of the strata near Berwick, do not reach to 

 Thornton, Shoreswood, Felkington, Etal, Gatherick. Greenowalls and 

 Nos. 5, 6, 7, and 8, are the beds worked at those coal-mines. 



N.S. Vol.9. No. 50. Feb. 1831. N Berwick 



