MUSEUM OF TIIE NATUKA.L HISTORY SOCIETY. 255 



The boundaries of the Northumberland and Durham coal-field 

 may be indicated on the west by an undulating line running 

 from the mouth of the Coquet to Ovingham on the Tyne, and 

 thence by "VVitton on the Wear to the Cockfield dyke, south of 

 which very few workings occur. It passes under the magnesian 

 limestone in the east of Durham, and is extended beyond the 

 line of the sea- coast. Through the influence of the 90-fathom 

 dyke a small strip of the Coal Measures runs parallel with the 

 Tyne valley to nearly the edge of the Pennine fault. Along this 

 line are the Stublick, Conewood, and Hartley Burn coal-fields. 



If the Gannister beds be taken as the Lower Coal-measures, 

 then without a doubt the Northumberland and Durham Coal- 

 measures belong to the Middle series. It must be borne in 

 mind that this Coal-field was excessively faulted and denuded, 

 especially in the south and south-east, before the Magnesian- 

 limestone was deposited, and there is no clue left to ascertain 

 whether the Higher Coal-measures were deposited over this 

 area, but the probabilities are that they were not. There is no 

 proof that this Coal-field was ever connected with the Yorkshire 

 Coal-field on the same meridians. 



Note. — The following books on the Fossil Plants of the Coal Measures 

 may be consulted : — 



Histoire des Vegetaux Fossiles, Brongniart, 1828-37. 



Fossil Flora of Great Britain, by Lindley and Hutton, 1831-1837. 



Catalogue of Paheozoic Plants in the British Museum, by R. Kidston, 

 1886. 



Catalogue of the Fossil Plants in the Hutton Collection in the Museum 

 of the Nat. Hist. Society, Newcastle-upon-Tyne, by Richard Howse. 



The Fossils occurring in the Coal Measures and Millstone 

 Grit are arranged in the Side Cabinets Nos. 28, 29, 30, 31, 

 32, 33, 34, 35, 36, 37, and in the Side Cases in the Gallery 

 of the Geological Room. Reference may also be made to the 

 Hutton Collection in the adjoining Floor-cases. 



