472 W. D. Varney — " Goal-halls," Ambergate, Derbyshire. 



This succession is similar to that occurring at Shore and other 

 well-known localities in Lancashire, where the Bullion or Upper- 

 Foot Mine contains numerous "coal-balls". 



No such concretions have been found and recorded from Derby- 

 shire, but the Alton Coal in the above-named exposure was found to 

 contain large nodules of iron pyrites. Some of these have centres 

 composed of calcite or calcareous material, suggesting that these 

 nodules were originally wholly calcareous. 



One of these specimens, on being sectioned, was found to have a 

 centre of calcite containing a Stigmarian rootlet, with the xylem (a) 

 fairly well preserved surrounded by the cortex (5), which, though 

 in a poor state of preservation, is still quite recognizable. Other 

 parts of the section contained plant tissue badly preserved, and 

 partly obscured by pyrites. Pyritization seems to have taken place 

 along lines of tissue running through the calcite groundmass as 

 seen at (d) and (c) in the diagram and in other parts of the slide. 



Section of nodule showing plant-tissues (somewhat diagrammatic), a, xylem of 

 Stigmarian rootlet; b, cortex ; c, d, other tissue, partly hidden by pyrites (e). 



At Bullbridge the Alton Coal is streaked with pyrites, which fills 

 cracks and joints, and the thin veins often join on to the nodules of 

 the same material. , Hence the pyrites was deposited after the 

 formation of the seam and its nodules. This fact, and the features 

 of the nodule section described, show that the pyrites is secondary, 

 and that the calcite and its petrified plant tissue were deposited 

 before the pyrites, which has replaced the former and largely 

 obliterated the vegetable tissue in so doing. In other words the 

 nodules were true " coal-balls ", now partly or wholly replaced by 

 iron pyrites. 



Hence the Alton Coal of Derbyshire contains nodules with petri- 

 factions, though they are mostly altered to iron pyrites. Thus the 

 seam shows a striking resemblance to the Bullion Seam of Lancashire, 

 as described by Miss Stopes and D. M. S. Watson.^ 



^ " On the Present Distribution and Origin of Coal-balls" : Proc. Eoy. Soc. , 

 vol. cc, p. 173. 



