6eal0gij iff tite §wtol (^mxlCuU, 



PART 4.-THE COAL MEASURES, 



Head at the General Meeting , December 2nd, 1875, 



WE now arrive at the most important of all our geological 

 deposits — that useful mineral, Coal. Immediately upon 

 the Upper Limestone shales we find a very thick deposit of Sand- 

 stones and beds of Coal of various thicknesses. They always appear 

 in basin- shaped depressions, and in very regular layers, having a 

 thickness of between 7000 and 8000 feet. 



Fig. 18. — Diagram of Bristol Coalfield. 



a Devonian— J Carboniferous Limestone— c Millstone Grit— ^ Lower Coal 

 Measures— e Pennant Grit-/ Upper Coal Measures— y Trias— A Lias— 

 i Inferior Oolite. 



On looking at our map, we find two or three of these Coal- basins 

 near the surface of the ground, and some hidden from our view by 

 several hundred feet of Triassic and Liassic strata. The longest of 

 these is in Gloucestershire, twelve miles long and four wide. All 

 over this fi(3ld are extensive Collieries at Iron Acton, Coalpit-heath, 

 Kingswood. Mangotsfield, and Pishponds. 



