Northumberland and Durham. 59 



Some of the members of this formation agree with those of the 

 Coal-field, viz. coal, shale and sandstone ; but other rocky masses 

 also attend the lead mine measures and serve to distinguish 

 them. These are the coarse grained sandstone called the millstone 

 grit, sandstone with impressions of marine shells, shale with the 

 encrinal fossil, the encrinal limestone, siliceous hornstone or chert, 

 and basalt in beds or in overlying positions. 



The four first of the following sections are those which I have 

 already referred to as representing not inaccurately the series of 

 beds in the mining field. The additional sections from Blanchland 

 resemble the upper part of the Aldstone moor section, and that 

 from Weardale the lower. I have added the section from Arken- 

 dale in Yorkshire for the sake of comparison. 



Section of the Lead-mine Strata at Hely Field on the river Derwent. 





Fs. Y. Pt. In. 







F>. Y. ft. is. 



Slate sill 



2 1 



Brought up 35 — 



Plate 



3 1 



Hard hazle 



. 2 1 



Different Girdle beds 



2 



Grey beds. (Thin layers oQ 



Plate 



2 1 — — 



slate clay and sandstone 



»Vl 



Freestone (fine grained sand- 



*' — 



alternating) . 



J 



sone) 



Freestone 







Coarse hazle 



1 1 



Plate 





I 



Plate and Blue whin 



1 



Hazle or Slate 





2 1 



Plate and Grey beds 



2 — 



Plate or Famp 





. 2 



Hard stone and Whin 



1 — 2 — 



Hazle and Plate 





2 1 



Plate and Whin 



112 — 



Plate 





. 2 



Plate 



2 I 



Hazle or Slate 





1 i 



Millstone grit . 



5 



Plate and Grey beds 



1 1 



Plate 



4 1 



Thin stratum of Grey beds 

 Fathom 



15 



Carried up 



36 



j 74 



h2 



