558 Notices of Memoirs—Professor W. S. Boulton— 
the South Staffordshire Coalfield, where the Middle Coal-measures 
are rapidly thinning, there are, if Mr. Kay’s observations are correct, 
signs of a non-sequence or local unconformity. The same is true, 
but on a larger scale, in the Symon Fault of the Coalbrookdale Coal- 
field,’ and is to be explained, if the above reasons are valid, by the 
rapid variation in thickness of the Middle-measures, due to the 
irregular floor upon which they rest, to the consequent sagging of 
the beds, and also to local subaqueous erosion. Further, such 
partial unconformities or non-sequences would generally indicate the 
proximity of that marginal fringe where the Upper-measures overlap 
the Middle and rest on pre-Coal-measure strata. 
The Middle and Upper Coal-measures of the Midlands record 
general but intermittent subsidence, with a considerable pause at the 
end of Middle Coal-measure time, followed by a much more general 
depression, as shown by the extended and overlapping sheet of 
Upper Coal-measures. But there is no evidence which I regard as 
convincing that regional elevation or great orogenic movements 
occurred until after the Upper Coal-measures were laid down. 
The floor upon which the Middle Coal-measures were deposited 
along the southern fringe of the Midland Coalfields was a sinking 
and already folded and denuded floor, and it is to be expected, there- 
fore, that these measures rest in submerged gulfs and estuaries, which 
would mean that some, at any rate, of the several coal basins were 
originally isolated wholly or in part, and their separation is not to be 
interpreted as due to folding and subsequent denudation. 
Dr. Newell Arber has argued that the Middle Coal-measures of 
Coalbrookdale, the Forest of Wyre, and the Clee Hills, were deposited 
in three separate basins, which as regards the Sweet Coal or Pro- 
ductive-measures were never continuous.” On the other hand, just 
as it is certain that the Productive-measures on either side of the South 
Pennines were originally continuous, so it is probable that as we go 
northward from this southern fringe the Productive-measures spread 
out into more extensive sheets... . 
As an example of such intensive geological work, I should like to 
refer to the detailed plotting by Mr. Wickham King of the Thick 
Coal of South Staffordshire on the 6in. maps. For more than 
twenty years he has been engaged in collecting and tabulating an 
immense number of levels and other data from colliery officials, and 
from old and sometimes half-forgotten borings; and he has now 
produced a contoured map and a model to the same scale, showing in 
great detail the folds and faults in the Thick Coal. In 1894 Professor 
Lapworth, to whose initiative this work was due, emphasized the 
value of such ‘‘plexographic maps” of coal seams, and predicted 
that such maps would be drawn in all the coalfields.* The data 
obtained in South Staffordshire also enable us to determine, at 
1 Mr. Wedd has recently described a similar break between the Middle and 
Upper Coal-measures of the northern part of the Flint Coalfield. (See Summary 
of Progress of Geol. Surv. for 1912, pp. 14, 15.) 
? Phil. Trans. Roy. Soc. London, Series B, vol. eciv, pp. 431-7: “‘ On the 
Fossil Floras of the Wyre Forest, etc.”’ 
3 Fed. Inst. Min. Eng., vol. viii, p. 357, 1894-5. 
