IxXXVi PKOCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jime I912, 



the ' unproved ' fields will by no means be plain and simple. The folds 

 rand faults by which the Coal-measures are affected, the variations 

 in the conditions of sedimentation during deposition, the irregular 

 surface on which the strata were deposited, the denudation to 

 which they have been subjected both during deposition and later, 

 €ach introduce complications ; and there is no likelihood that the 

 ■concealed coal-basins will be in any way more simple than the 

 exposed ones. Yet it is these details of structure which will make 

 all the difference between success and failure, profit and loss, in 

 the development of the fields. 



A typical coal-basin includes five more or less distinct regions, 

 and it is interesting to compare the relative importance of 

 <each of these. In the first place, there is the region of profitable 

 working within which productive Coal-measures exist at a depth 

 not too great to be easily reached and worked. In the second 

 place, there is the region where synclinal conditions are in excess 

 and the measures have been carried down too deep for profitable 

 working. In the third place, there is the region where anticlinal 

 conditions are in excess, the underlying rocks have been brought 

 to the surface by folds or faults, and the Coal-measures which once 

 covered them denuded away. In the fourth place, there is the 

 region where no deposition took place in Coal-measure time, owing 

 to the irregularly upstanding land-masses of jDre-existing rock to 

 which the Coal-measures are unconformably related. And in the 

 fifth place, there is the region in which the Coal-measures, having 

 l^een deposited near to the old land areas in later Carboniferous 

 time, are barren and not worth working. Each of the regions 

 may be made up of several more or less distinct areas, the term 

 * region ' being employed as a collective designation for the sum of 

 those areas in which similar conditions obtain. 



An estimate founded on these lines could easily be drawn up for 

 each and all of the visible British coalfields, and it might be useful 

 in giving some rough idea as to the average conditions w^hich 

 might reasonably be expected to recur in the concealed areas under 

 the Xeozoic cover. But it would not be well to place much reliance 

 on figures so obtained. 



Nor, on the other hand, would much be gained if an attempt 

 were made to calculate the possible amount of coal, which might 

 be expected to exist in the problematical 2700 square miles of coal- 

 area that may lie concealed under the jN'eozoic rocks, on the basis 

 of the amounts which have been taken from, jj?«s those that are 

 still left in, the visible Palaeozoic area. One consideration alone, 



