Vol. 68.] ANNIVEESAEY ADDEESS OF THE PEESIDENT. IxXXvii 



not to mention others, serves to eliminate confidence in such lignres 

 as a working basis. We ma)- state it as follows : — 



If we draw a geological section across Ireland and England, it 

 Avill be found that the average denudation-line cuts deeper into the 

 folds of the Palaeozoic rocks in Ireland on the west than in Great 

 Eritaiu on the east. If this relationship may be exterpolated under 

 the Xeozoic cover of England, the depth of the troughs is likely on 

 the whole to increase towards the east and south. Thus, in addition 

 to the thick Neozoic cover, the miner may have to deal with deeper 

 synclines in the coal basins. 



(d) Sources of Information. 



In the Triassic and Super-Triassic eastern and southern area of 

 England, our knowledge of the concealed outcrop of the Palaeozoic 

 Tocks is limited to four sources of information, each of which 

 provides us with a certain but not very large amount of knowledge. 



Eirst, we have the visible plunging of the structures of the 

 Palaeozoic rocks under the newer cover. Sometimes this occurs 

 without disturbance, but more usually it is complicated by faulting, 

 and especially by boundary faulting. Moreover, as the axes of 

 folding, and even the lines of the faults of the older rocks, do 

 not run straight but along curves of types which have not yet 

 been reduced to simple general laws, the prolongation of visible 

 structures under an unconformable cover must ever be a com- 

 plicated phenomenon, and any attempt to forecast it is a matter 

 into which speculation will enter largely. The question is further 

 complicated by variation in thickness and content, and by the 

 occurrence of unconformities and overlaps amongst the Palaeozoic 

 rocks themselves. It is largely owing to these circumstances 

 that working on the concealed fringes of exposed fields has 

 always been an uncertain process, carried out timidly and with 

 great caution. 



The Eeport of the Commission on the unproved coalfields 

 should be carefully read by every geologist interested in the British 

 coalfields. It contains a treatment by Professor Charles Lapworth 

 of the buried extensions of the groups of coalfields of Central 

 England, giving a most lucid and convincing picture of the condi- 

 tion of matters which there exists under the Triassic cover. 



Secondly, we have the evidence yielded by borings put down 

 through the newer strata, and penetrating far enough to reach . 

 the Palaeozoic rock-floor under the cover. A glance at the map 

 published by the Coal Commission, which gives all the principal 



