lOlG] on The Search for New Coal-Fields in England 633 



1911, and the annual output up to date is given by the Home Office 

 as follows : — 



Year. Tons. 



1911 150 



191-2 1,099 



1913 59,203 



1914 130,440 



1915 158,389 



349,281 



During the last few years many borings have been put down and the 

 limits of the coal-field approximately determined. The information 

 at our disposal is sufficient to enable us to realize the general struc- 

 ture of the strata. The Secondary and Tertiary strata which form the 

 blanket are approximately horizontal, but the coal measures and 

 other palaeozoic rocks below them are folded and disturbed. The 

 surface of the older rocks was planed off to a surface, known as the 

 palaeozoic floor, which is remarkably even, but slopes gently down- 

 wards to the south or south-west. Upon this floor the newer strata 

 repose, and thicken as it descends, until they reach a thickness which, 

 up to the present, has proved a bar to farther exploration. The 

 surface configuration gives no clue to the structure of the palaeozoic 

 rocks, and statements that coal has been found at small depths in this 

 part of England are based on erroneous identifications as coal of the 

 lignite, which is common in some of the Secondary strata. 



For a determination of the structure of the older rocks we are 

 largely dependent upon the fact that many of the bore-holes have 

 reached the top of the carboniferous limestone. They have passed 

 directly from productive coal measures into the limestone, thus 

 proving the absence of millstone grit. There is, therefore, a gap in 

 the strati graphical sequence, and possibly some slight discordance of 

 dip between the coal measures and the limestone, but the form of 

 the limestone surface is, notwithstanding, a matter of much signifi- 

 cance. I have, therefore, prepared a map (Fig. 4) on which the 

 borings are indicated, and on which the depth below sea-level of every 

 pointat which the limestone has been touched is shown. 



When these entries had been made upon the map, it became 

 apparent that there was sufficient evidence for drawing contour-lines 

 in the limestone surface with a fair approximation to the truth. The 

 lines are drawn at intervals of 500 feet from a level of 1,000 feet 

 below the sea down to a level of 3,500 feet. They enable us to 

 visualize the surface as a trough, the axis of which ranges a little 

 west of north. We can see, further, that it is only in this trough 

 that there is any room for coal measures. Towards the north it rises 

 until rocks older than the carboniferous limestone come up into 

 contact with the Secondary strata ; southwards, it descends con- 

 tinuously as far, at least, as the south coast. Eastwards the limestone 



