Prof. T. Rupert Jones — Address. 567 



and even altogether a hard sandstone (' ganister '). It varies in colour from black to 

 white; and is from six inches to ten feet or more in- thickness. A characteristic 

 feature is its being penetrated in all directions by the stigmarian roots and rootlets 

 of the trees {Sigillaria, Lepiclodendron) that grew on it when it was the soil of the 

 coal forest, having been slowly deposited by the quiet, shallow, muddy waters that 

 succeeded the deposition of shale or sandstone by waters with stronger currents, 

 these last terminating one of the periodical disturbances to which the many stages 

 of gradual subsidence gave rise. Every coal-bed (or coal-seam, according to the 

 application of those words to either a simple or compound layer of coal) lies on 

 a more or less distinguishable ' underclay ' ; but this is often omitted to be recorded 

 in coal-mining sections and documents.^ Sometimes an underclay forms a roof of 

 a coal ; but it is the seat- earth of a coal lying on it. 



Denudation. — Among the many examples of denudation in the Coal-measures, 

 coal-beds have been washed away from their underclays ; but these latter are so 

 greatly toughened by their contained network of roots that they have more effectually 

 resisted denudation. Both coals and underclays, however, were not unfrequently 

 destroyed, or, at least, deeply and widely channelled by contemporaneous floods and 

 rivers; for not only are the 'horses,' 'lows,' and 'washes' such watercourses, but 

 the occiurrence of pebbles of coal and small detrital particles scattered through some 

 of the sandstones are due to similar denudation. - 



Sir J. W. Dawson, in ' Acadian Geology,' 1868, p. 139, states :— " The occasional 

 inequalities of the floors of the coal-beds, the sand and gravel ridges which traverse 

 them, the channels cut through the coal, the occurrence of patches of sand, and the 



insertion of wedges of such material splitting the beds, are constantly 



represented in modern swamps and maishes, more especially near their margins, 

 or, where they are exposed to the effects of ocean storms or river inundations." 

 The great thickness of coal and carbonaceous shale in the Albion Coal-measures at 

 Plcton, Nova Scotia, were formed in a depression separated by a shingle bar 

 (conglomerate) from the more exposed flats outside.'^ 



9. Fossils of the Coal-measures of South TFales.— An examination, or even an 

 enumeration, of the fossils would be much more than we have time for now, 

 whether vre took in hand the plants or the animals. 



I. Of the characters of the former* we have indicated some particulars, such as 

 facts about the spores and roots of the gigantic trees of which the humble Selaginella, 

 Isoetes, Sphagnum, and Equiseticm are the living representatives. Descriptions of 

 their roots, trunks, leaves, woody and other structures have been given to the world 

 by both Foreign and British palajobotanists in numerous goodly memoirs and 

 volumes, illustrated with excellent plates ; and the many ferns, tree-ferns, and 

 cycadaceous plants (the last known by their fruits chiefly) have been well described 

 and figured. Kidston's ' Catalogue of the Carboniferous Plants in the British 

 Museum ' gives full references to many of the above, and the others are well known. 

 With increased knowledge, the supposed dome-like, long-armed, stigmarian plants, 

 with subaqueous leaves or processes, either floating on or in the water, or growing 

 on the mud, have become the depressed stools, dichotomous roots, and innumerable 

 long, narrow, leaf-shaped rootlets of Sigillaria and Lepidodendron (Binney and 

 others). C. Grand'Eury, however, still distinguishes some perfectly aquatic and 

 peculiar plants, which floated in the water with their roots trailing on the bottom ; 

 and of Stigmaria he holds the opinion that it indicates a formation in deep water, 

 contrary (as he says) to what is generally stated. ^ The supposed palms have disap- 

 peared in the explanation that the supposed fruits are only the marks of compressed 

 gas bubbles fixed during their escape from the foetid black, decomposing mud." 



sist mainly of minute, rutiliferous, mica-like flakes, regarded by him as of secondary 

 origin, made from the original components of the stratum (Geol. Mag. 1890 and 

 1891). Mr. Hutchings kindly informs me that, of the numerous fireclays which he 

 has examined, several are being used for brick-making (Letter, May 20, 1891). 



1 De la Beche, Mem. Geol. Survey, vol. i. pp. 173 and 177. 



2 Logan, De la Beche, Buddie, and others. 



3 Dawson, Q.J.G.S. vol. x. p. 46. 



* A useful compendium of our knowledge of coal-plants in 1863, by Professor 

 John Morris, was published in the Proceedings Geol. Assoc, of that date. 



* Mem. presentes, etc., Acad. Sciences, etc., France, vol. xxiv. No. 1, 1877 ; and 

 Annales des Mines, ser. 8, Memoires, vol. i. 1882, p. 161. 



6 Carruthers, Geol. Mag. 1870, p. 215. 



