HUGHES : INGLEBOROUGH. 
137 
Why fossils ai-e so scarce, so obscure, and of such small use 
for purposes of correlation in these South Wales beds I cannot 
say, but in that respect also they resemble our pockets of con- 
glomerate, sandstone, and shale under Ingleborough, or the great 
red conglomerate of the borders of the Lake District. 
Cross the Bristol Channel, and there you find the equivalents 
of the " Brown stones " of Carmarthenshire split up by shales 
and limestones in which there are plenty of fossils, but in the 
great sandstones of the Devonian they are more scarce, 
Now, we have got a suggested correlation. 
The Old Red of Hereford is not Devonian, but the Devonian 
of Abergavenny creeps across the Old Red unconformably. There 
was a mountainous district in the North of England and North 
Wales, while South Wales and Devonshire sunk beneath the 
Devonian Sea. By-and-by that sea cut down the mountains of 
the northern part of our island and determined the level of the 
sea-plain on which Ingleborough rests while the Lake District 
still stood above it. 
If this be the true story, this sea-plain at the base of Ingle- 
borough is of Devonian age, and the pockets of sediment which 
lie in it are the last bits of sediment which can be referred to 
the Devonian before the widespread changes which then took 
place ushered in the conditions which allowed of the deposition 
of the Lower Carboniferous Series. 
Many are the questions in Physical Geography which may 
be studied in this wonderful district. 
One to which I have had to refer, and which seems at first 
to be connected with the sea-plains which we have been consider- 
ing, is the origin of the ledge of Mountain Limestone on which 
the upper half of the mountain rests as on a table (Plate XXII.). 
If all the mass of Yoredale shales, sandstones, (fcc, and overlying 
Millstone Grit were removed the resulting feature would be much 
like what we have now, namely, a capping of hard rock which 
might or might not have a corresponding flat top seen on the 
adjoining hills. What w^e have to look into is this : Is this 
terrace of limestone the margin of a sea-plain which washed the 
