TRANSACTIONS OF SECTION C. 621 



series ; 2. Lower Pennant series ; 3. White-ash series ; and gives the following 

 plan in addition : — • 



1. Upper or Penllergare series, more than 3,400 feet. 



2. Pennant-grit (Swansea), 3,246 feet. 



3. Lower Coal-measures, 450 to 850 feet. 



At p. 219 he reviews the whole of the series as — 



Coal-measures . . . • - 

 Millstcne-grit (' Farewell Rock ') 

 Yoredale Rocks ? (' Gower Shale ') 

 Scar Limestone ... 

 Lower Limestone Shales 



Feet. 

 11,000 



300 

 1,600? 

 1,900 



400 



15,200 



making the Coal-measures more than 1^ mile thick, and the whole series more 

 than 2i miles. 



Looking at these Coal-measures alone, and considering that slow depression 

 accompanied their formation, the mind is strained in estimating the time required 

 for the gradual subsidence to 10,000 feet, with shallow water always in place, 

 and jungle growing steadily after jungle, inundation following inundation at 

 intervals, — and is somewhat confused in reasoning on the possible causes and the 

 exact processes by which not only the sinking of this region of the earth's crust 

 was brought about, but how, in turn, the 10,000 feet of new accumulations and 

 deposits were raised into the great undulations, which Professor Ramsay has 

 described and depicted in his Memoir before mentioned, and how and when they 

 were slowly worn down day by day into the present beautifully varied surface of 

 South Wales and adjacent country. 



I may bore remark that the analogous coal-field of Nova Scotia, investigated 

 by Sir W. E. Logan, Sir J. W. Dawson, and others, has a thickness of 14,570 

 feet, including seventy-six seams of conl and ninety distinct Stigmarian underclays. 



Mr. W. 'Galloway communicated, in 1885, to the Cardiff Naturalists' 

 Society ^ some valuable observations on both the vertical and the horizontal 

 occurrence of difierent coals in South Wales ; and showed by a map (pi. iii.) 

 where the ' steam-coal ' mainly exists in the large eastern third; the ' intermediate 

 coal' in the narrow jn/ffrfZe third; and 'anthracite' in th.Q western third of the 

 Glamorgan-lMonmouthshire area. He refers to the gradual transition from 

 bituminous to anthracitic coal along a hypothetical plane passing through the 

 coal-field, with its major axis lying E.N.E.-W.S.W., and its minor axis dipping 

 at a very low angle towards S.S.E. He accepts Professor Geikie's tabular scheme 

 of the strata at p. 24. Mr. W. Galloway has favoured me with the following 

 remarks on the vertical place of the several kinds of coal in the series:— 'The 

 long-faminfi bituminous seams are about 700 yards higher in the ground than the 

 semi-bituminous seams ; the semi-bituminous, or good steam-coal seams are 200 

 or 300 yards above the dry steam-coal seams ; the last are perhaps 300 yards 

 above the bastard anthracites; and tl '>>e inferior anthracites may be 400 yards or 

 more above the perfect anthracites. You have thus somewhere about, say, 1,500 

 or 1,600 yards from the long-flaming coals to the anthracites. It may be a good 

 deal more in some parts of the coal-field ; but, as the deepest shaft is only about 

 800 yards, we cannot get a direct measurement.' 



Of these three sorts of coal— the long-flaming dry coals above have some seams 

 suitable for gas-making ; the middle are caking coal, good for making coke ; the 

 others produce dry steam-coal and anthracites. 



6. Output of Coal in South TFaZes.— The following is the official account of the 

 quantity of coal raised in South Wales last year as compared with that got ten 

 years ago : — 



> Trans., vol. xvii., 1886, pp. 20-34. 



