36 



thus fully accoimting for the absence of coal- shafts in a defi- 

 nitely determined zone along and around the northern portion 

 of the Bristol Coal Basin. Nevertheless it must not be supposed 

 that the coals and coal measures do not exist in all their 

 integrity below this belt of Pennant; but perhaps \mtil a scarcity 

 of coal is felt in this region, it is questionable if ever any ad- 

 venturer vpill be bold enough to win the coal below, by piercing 

 or sinking through this Sandstone barrier. 



Fig- 4. — Section showing why Pits are worked below the Pennant, or above it, as the case may be, 

 and also the area now unworked beneath the Pennant. 



Having thus generally, yet definitely, fixed or defined the 

 position and extent of the district traversed by this Pennant, 

 and which Rock, as I believe, determines the chief Iron- 

 producing ground, I will now enter upon the more immediate 

 subject of my paper, dividing it under its chief heads, viz. — 

 Position op the Iron, and 

 Mode op Occureence, &c. 



Geological Position and Mode of Occurrence of the Iron Ores. — • 

 There are numerous localities in Gloucestershire where Iron 

 Ores occur under various conditions, and are largely developed 

 and worked, and which in a popular sense may be designated 

 according to the Geological formations in which they occur. 

 Indeed most of the Palaeozoic sub-formations of the counties of 

 Gloucester and Somerset possess ores of Iron which may be 

 recognized or associated with the rocks from whence they come, 

 such as Gothite or Hydrous Oxide ; Brown Haematite, {'Hydrous 

 Oxide of Iron) from the Carboniferous Limestone, Millstone Grit, 

 and Pennant; also Limonite, another variety of brown Hydrated 

 Peroxide, occurring in the Limestones and Sandstones ; and the 

 massive Argillaceous or Clay Ironstones (Siderite)* occvirring in 



* The most valuable of our Iron ores, being easily smelted, as the clay and lime 

 which is associated with it acts readily as a flux. This ore is the Blackband when 

 charged with Carbonaceous matter, and occurs in- almost unlimited quantities with 

 our Coal seams. The amount of Protoxide of Iron varies from 20 to 40 per cent. 

 Four-fifths of the Iron of this country is produced from this variety (Siderite. ) 



