130 
HUGHES : INGLEBOROUGH. 
plenty of room for it all there, for it would take about 36 times 
all the land that stands above the sea to fill up its bed. 
The waves plane all down for some 60 or 100 feet more, 
and there the surface is protected from further waste. 
The plain of the Yorkshire Fells is one of these sea-plains 
now lifted up some 2,000 feet more or less above sea level. If 
we want evidence that it is not merely a stage in sub-aerial 
waste, determined by the same hard and widespread bed which 
has arrested the action of tlie frost and ice and rain and streams, 
we have only to examine the sequence of rocks more closely to 
obtain the proof. The bed that forms the hill tops is not always 
the same. Even from Ingleborough to Penyghent we creep on 
to higher beds, and if we trace the beds further north we shall 
still find different members of the series capping the Fells. The 
evidence is clear enough, even in the nearly horizontal strata of 
the Carboniferous rocks of the district north of Clapham. But 
we have further proof, and clearer, if we just cross to the north- 
west from Ingleborough on to the Silurian Fells near Sedbergh 
(Fig. 1). There the rocks are no longer nearly horizontal, 
but roll up and down in faulted folds, yet the tops of the hills 
are all planed off to the level of the sea-plain, which is touched 
by the Carboniferous Fells north of Clapham. From that it 
may be traced always at about 2,000 feet above sea level to the 
base of the Lake Mountains, which are an island, itself the last 
remnant in that part of England of a now higher sea-plain, 
undulating at about 3,000 feet above sea level. This is not the 
only example of these two sea-plains. In Wales the lower or 
2,000 foot plain touches the tops of all the higher mountains of 
South Wales, and, leaving Plinlimmon as an island in Central 
Wales, laps round the higher or 3,000 foot plain of Snowdonia, 
just as our 2,000 foot plain runs up to the 3,000 foot plain of 
the Lake District. 
Surely we have here a grand subject for further research. 
What is the age of these two plains ? What basement bed 
derived its pebbles from the shore of the sea that arrested 
denudation at the 2,000 foot plain of Yorkshire? and what forma- 
