Frof. T. Rupert Jones — Address. 523 



between two and across one (just north of Swansea). The favourable 

 position for mining some of the measures is due to the local angle of dip 

 in the synclinal strata ; and, indeed, without the anticlinal arrangement 

 some of the coals could never have been reached even by deep mines. ^ 



Mr. Etheridge (in his new edition of PhiUips's "Manual of Geology," 

 1885, p. 238) mentions that in the southern part of the western moiety 

 the Coal-measures have a thickness of 11,000 feet ; and that on the 

 northern side of the anticlinal axis there they are 7000 feet thick, and that 

 near Britton Ferry, in the middle, they diminish to 4800 feet on that side. 



Taking the whole basin or trough, it may be roundly said that in the 

 north-east side the coals are mainly coking or partly bituminous ; to the 

 west and north-west they are anthracitic ; and in the south bituminous or 

 gaseous ; and more especially that " in the Aberdare area the coals are very 

 free-burning, but at the same time smokeless ; hence their importance for 

 steam purposes, especially the Aberdare four-foot steam-coal." - 



The physical features and structural condition of the South- Welsh coal- 

 field, also the occurrence of fossils, were succinctly treated of by G. P. 

 Bevan in the " Geologist," vol. iii. 1860, pp. 90-99. 



The order and thickness of the strata belonging to the coal-field of 

 South Wales as given in Geikie's " Textbook of Geology," 2nd edit., 1885, 

 p. 742, are (for Glamorganshire) : — 



Upper series : sandstones, shales, etc., with 26 coal-seams, more than 3400 feet. 



Pennant grit : hard, thick-bedded sandstones, and 15 coal-seams ... 8246 ,, 



I .ower series : shales, ironstones, and 34 coal-seams 450 to 850 ,, 



Millstone grit. 



The Coal-measures are thus estimated at 7496 feet, or nearly 1-^ mile 

 in thickness, besides the Millstone-grit and the Carboniferous or Mountain 

 Limestone occupying a still lower position. 



DitFerences of observation or of opinion from time to time have caused 

 different estimates. In 1855 Professor J. Phillips, who took a very strong 

 interest in the geology of the coal-fields, published the following measure- 

 ments (in his "Manual of Geology," 1855, p. 201) as representing only a 

 general view, and he indicated that nearly 12,000 feet thickness may occur 

 near Llanelly : — 



T>lanelly series, with several beds of coal 1000 feet. 



Penllera^are series of shales, sandstone and beds of coal — 110 beds ; 



26''beds of coal 3000 ,, 



Central series (Townhill sandstones of Swansea = Pennant-grit of the 



Bristol coalfield)— 62 beds ; 16 beds of coal 3246 „ 



Lower shales, coals, and ironstones (Merthyr) — 266 beds ; 34 beds of 



coal 812 „ 



8058 

 Farewell Rock and Gower Shales, above the Carboniferous Limestone. 



Professor HulP gives about 1200 to the Coal-measures, with twenty- 

 five seams of coal of two feet thickness and upwards ; making a total of 

 eighty-four feet of workable coal. In 1881 Professor Hull calculated that 

 there remained about 32,166 millions of tons of available coal, which 

 might possibly last for more than 1000 years at the present rate of 

 consumption. 



Mr. E. Eogers, in the " Memoirs of the Geol. Survey : Iron-Ores," part iii. 

 1861, p. 169, divides the Coal-measures of South Wales into an Upper and 

 a Lower series, with the hard siliceous sandstone (locally a conglomerate), 

 known as ' Cockshute ' and ' White Rocks ' between them. The upper 

 measures, he says, are mostly micaceous sandstones, locally known as 



1 Ibid, chap. i. 2 Etheridge, 1885. p. 238. 



3 " The Coalfields," etc., 1881, p. 108. 



