274 Calcareous Nodules (‘ Coal Balls’) and Their Significance. 
frequently , in brackish — water swamps, those which formed the coals 
containing calcareous nodules grew in swamps, the waters of which were 
more definitely salt. 
‘ Floor ’ nodules contain only roots. ‘ Seam ’ nodules are composed 
of petrified swamp -plants . Some, but not all, 1 roof ’ nodules include 
plants; these may be either swamp-or land-plants. 
The absence of growth -rings from the wood of the stems suggests a climate 
which was of fairly uniform temperature. 
A study of some nodules suggests that eleven to twelve feet of vegetable 
debris was eventually reduced to form each foot of coal. 
Floor ’ and ‘ roof ’ nodules contain a much greater proportion of 
silicates than ‘ seam ’ nodules ; this represents sand and accounts for part 
of the ash in coal. 
The fact that some ‘ roof ’ nodules contain land plants does not militate 
against the stratigraphical use of plant -incrustations found in the immediate- 
roofs of coal-seams in general. 
LITERATURE . 
Absalom, R. G., ‘ The Lower Carboniferous Coal Ball Flora of Haltwistle, 
Northumberland,’ Proc. IJniv. Durham Phil. Soc., Vol. viii, 1929, 
P- 73 - 
Binney, E. W., ‘ On Some Fossil Plants showing Structure from the 
Lower Coal Measures of Lancashire,’ Quart. Journ. Geol. Soc., 
Vol. 18, 1862, p. 106. 
— ‘ Observations in the Structure of Fossil Plants found in the Carboni- 
ferous Strata,’ Palaeont. Soc., London, 1868, p. 1. 
Cash, W. and T. Hick, ‘ A Contribution to the Flora of the Lower Coal 
Measures of the Parish of Halifax, Yorks.’, Proc. Yorks. Geol. 
Polyt. Soc., Vol. 6, 1873. 
Chapman, F., ‘ On Concretionary Nodules with Plant -remains found in 
the old bed of the Yarra at S. Melbourne and their resemblance to 
the Calcareous Nodules known as “ Coal Balls,” ’ Geol. Mag., 
1906, p. 553. 
Hirmer, M., ‘ Ueber Vorkommer und Verbreitung der Dolomitknollen 
und deren Flora, Congr. Stratig. Carbon. Heerlen, 1927 ; Leige, 1928. 
Hooker, J. D. and E. W. Binney, ‘ On the Structure of Certain Lime- 
stone Nodules enclosed in seams of Bituminous Coal, with a 
Description of some Trigonocarpons contained in them,’ Phil. 
Trans. Roy. Soc. Lond., Vol. 145, 1855, p. 149. 
Jeffrey, E. C., ‘ Coal and Civilisation,’ London, 1925. 
Koopmans, R. G., ‘ Researches on the Flora of the Coal Balls from the 
Finefrau-Nebenbank horizon in the Prov. Limburg, Geol. Bur. 
Nederland, Mijngebied, 1928. 
Kendall, P. F., in J. W. Evans and C. J. Stubblefield’s ‘ Handbook 
of the Geology of Great Britain,’ London, 1929. 
Lomax, J., ‘ On the Occurrence of the Nodular Concretions (Coal Balls) 
in the Lower Coal Measures,’ British Assoc., 1902 (Belfast), p. 81 1 — 
abstract of paper read. 
Stocks, H. B., ‘ On the Origin of Certain Concretions in the Lower Coal 
Measures,’ Quart. Journ. Geol. Soc., Vol. 58, 1902, p. 46. 
Stopes, M. C., ‘ Plant-containing Nodules from Japan,’ Quart. Journ. 
Geol. Soc., Vol. lvi, 1909, p. 195. 
Stopes, M. C. and D. M. S. Watson, ‘ On the Present Distribution and 
Origin of the Calcareous Concretions in Coal-seams known as Coal- 
balls,’ Phil. Trans. Roy. Soc., Lond., B, Vol. 200, 1908, p. 167. 
Strahan, A., ‘ On the Passage of a seam of coal into a seam of Dolomite,’ 
Quart. Journ. Geol. Soc., Vol. 57, 1901, p. 297. 
Weiss, F. E., ‘ On the Occurrence, Distribution and Mode of Formation 
of the Calcareous Nodules found in Coal Seams of the Lower Coal 
Measures,’ British Assoc., 1906 (York). 
The Naturalist 
