A HISTORY OF DURHAM 



Shales, sandstones (often including a specially thick set of beds) and 

 a thin 3 foot thick limestone, No. 156, known as The Small Limestone 

 and very constant, bring us to 



No. 153. T'he Great or Main Limestone ', the thickest (about 72 

 feet thick) and by far the most important of the higher (or true ' Yore- 

 dale ') limestones of the Bernician Series. As an ore-bearing horizon it 

 is second to none, and the same may be said of it as regards quarrying. 

 For centuries a large population has been supported by the work neces- 

 sitated by it, specially in the Stanhope district of Weardale. Between 

 Wolsingham and Frosterley this great calcareous formation is to be seen 

 dipping beneath the bed of the Wear, and its outcrop can be followed 

 thence for miles, forming a clear feature dotted with quarries as far as 

 the eye can reach both to the north and to the south. Considering 

 the extreme variability of most of the beds of limestone from the 

 midlands northwards the regular constancy of this horizon is remark- 

 able. It can be traced with certainty from west Yorkshire to north 

 Northumberland, and even, if recent correlations be accepted, to the 

 central valley of Scotland between the Forth and the Clyde. Its thick- 

 ness is greatest in the Durham area, from which it thins away south, 

 west and north. Whether it thickens or thins to the east it is not yet 

 possible to say, though the Chopwell boring, which will be referred to 

 again further on, seems to show that it will prove to thin away in that 

 direction likewise. Naturally so thick a limestone is made up of many 

 layers, and to these names have of course been given by the generations 

 of quarrymen who have been engaged in destroying them. The names 

 adopted in the Frosterley quarries are quaint and sometimes descriptive. 

 They are perhaps worth citing. They are as follows, in ascending 

 order : 



(1) THE BOTTOM POST. This layer is frequently entirely made 

 up of the fossil Monticuliporid coral Chaetetes byperboreus. 



(2) THE NEWCASTLE POST. 



(3) THE JACK POST. 



(4) THE YARD POST. 



(5) WHALEY. 



(6) STIFF DICK. 



(7) DUN JIM. 



(8) DUN KIT'S BASTARD. It may be noted that the term 

 ' bastard ' in the sense of inferior or impure is common in the north in 

 connexion with workable stone. 



(9) THE DUN KIT POST. 

 (10) THE FIVE THIN POSTS. 



(n) THE BLACK BEDS. It is in this part of the Great Limestone 

 that the rich ' middle ' flat of lead ore occurs. 



(12) THE TOMS or TWEE TOMS. 



(13) THE THICK COCKLE POST. 



(14) THE THIN COCKLE POST. These two fossiliferous courses are 

 perhaps the most valuable of the whole mass. One of them is full 



8 



