343 



THE OCCURRENCE, DISTRIBUTION, AND MODE OF 

 FORMATION OF THE CALCAREOUS NODULES 

 FOUND IN COAL SEAMS OF THE LOWER COAL 

 MEASURES.* 



Prof. F. E. WEISS. 



The petrified remains of coal-measure plants which, through 

 the investig-ations of Binney and Williamson, of Scott, Seward, 

 and Oliver, have so largely increased our knowledge of the past 

 history of the vegetable kingdom, were chiefly contained in 

 calcareous concretions (the so-called ' bullions ') found in certain 

 seams of the Lancashire and Yorkshire coalfields. As first 

 described by Binney, they were to be found in three seams in 

 Lancashire : in the ' Upper Foot ' or ' Bullion ' Mine, in the 

 Canister coal, and in a very narrow seam of a lower horizon. 

 Some confusion, however, exists with regard to the two former 

 seams, owing to their union to form the ' Mountain Four Foot ' 

 seam, and there seems considerable doubt as to the occurrence 

 of coal-balls in the Canister coal. Indeed, it would seem now 

 generally accepted that true coal nodules occur only in one 

 single horizon.! The nodules or bullions occurring in this 

 Upper Foot seam (correlated by Bolton with the ' Hard Bed ' 

 seam of Halifax) vary from an inch to a foot in diameter. They 

 are concretions, consisting mainly of carbonates of lime (45 to 

 70 per cent.) and of magnesia (10 to 20 per cent.), with small 

 quantities of oxide and sulphides of iron. Sometimes they are 

 so numerous as to render the coal utterly useless, and they may 

 be found to occur over a space of several acres. They contain 

 a tangled mass of plant remains, often in a state of excellent 

 preservation. Shells are not found in these nodules, but are 

 very common in similar nodules found in the roof of the seam. 

 According to Binney, the occurrence of nodules in the coal is 

 always associated with that of fossil shells in the roof, and the 

 nodules may therefore probably be formed by calcareous salts in 

 solution in water, which became ag^gregated round certain 

 centres in the submerged peaty mass of vegetable matter. A 

 similar mode of formation has been suggested for the calcareous 

 nodules (Dolomitknollen) which occur in certain seams of the 

 Westphalian coalfield, where marine shells are found in the shaly 

 roof of the seam. Stur has also noticed the same in the case 



* Abstract of paper read to Section K of the Meeting- of the British 

 A.s.sociation, York. 



t See Lomax, ' Annals of Botany,' 1902. 



igo6 September i. 



