Paleo-Geological and Geographical Maps of the British Islands. 275 
continuously across the south of Scotland to join those of the north of England. It 
has been assumed that some of the higher parts of the southern uplands were 
uncovered by Upper Carboniferous strata, as they certainly were by those of the 
preceding stage. Nearly the whole of Ireland was originally covered by coal- 
measures. * 
Formation of Coalfields.—Out of the original extensive tracts of coal-measures, 
almost conterminous with the boundaries of submerged areas shown in figure 
2, the existing coalfields have been constructed. As compared with the original 
areas, their size is small indeed. This is due to the extensive denudations which 
took place—first, at the close of the Carboniferous period ; second, at the close of 
the Permian period ; and thirdly, in still more recent times. Ireland has suffered 
most of all, owing to the absence of mesozoic strata ;f only small isolated patches, 
monuments of former more extended tracts, have been left behind, 
The possible positions of three coal-basins south of the Thames valley are shown in 
figure 2, very much the positions originally indicated by Mr. R. Goodwin-Austen.{ 
The sub-Wealden boring, intended to ascertain the nature of the Palzeozoic strata 
along this tract, unfortunately was stopped before passing into Palzeozoic rocks. The 
position of the coal-measures—proved under the Lias by boring at Burford—is also 
shown in Figure 1, but it is impossible to determine the form of this coal-basin. 
Distribution of Land and Water.—Little need be added to what has already been 
said on this point. As compared with the Lower Carboniferous epoch, the land 
areas become contracted owing to subsidence, but the thickening of the strata, both 
towards the north-west and south-west of England, indicate the existence of 
extensive tracts of land, and sources of sediment, in those directions.§ The waters 
which overspread the plains were disconnected from those of the ocean, except at 
intervals, though possibly at all times bordering on the sea-level of the period. 
Puate X XIX. 
The Permian Period. 
The Permian beds are restricted to the central portions of the British Isles, and 
apparently were never deposited over any part of the extreme northern, western, 
or southern districts, or of the adjoining continental areas. According to the view 
of Sir A. Ramsay, the magnesian limestone of the north of England was formed 
* See “ Physical Geology and Geography of Ireland,” pp. 43, 149, 163. + Ibid., p. 164. 
t Quart. Journ. Geol. Soc., vol. xi. (1855.) The same author places the line of possible coal-measures 
under the Thames valley, but the London borings for water do not appear to me to bear out this view. 
See Map, No. 6, to accompanying evidence before the Royal Coal Commission. 
The extension of the Coal-measures beneath newer formations is indicated by the lighter shade in 
figure 1. 
§ See, on this subject, my paper “ On Iso-diametric Lines, &c.” Quart. Journ. Geol. Soc., vol. xviii. 
pp. 127-146 (1862). 
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