HUGHES : IXGLEBOROUGH. 
131 
tion was laid down in the sea that crept across the 3,000 foot 
plain of Cumberland ? Which way did that sea advance, from 
north, or south, or east, or west ? 
Geologists, who regarded these phenomena chiefly from the 
point of view which is forced upon us as we stand upon the 
coast line, and watch the tremendous power of the waves as they 
batter the cliffs and lash the shore, called the level surface so 
produced a Plain of marine Denudation. 
But there is another set of agents at work reducing all the 
protuberances of the earth's surface. The air, and rain and 
rivers, and glaciers, and changes of temperature and moisture are 
breaking, dissolving, transporting everything down to the sea. 
There it can do no more ; the sea arrests all further sub-aerial 
waste and reserves for itself the work of removing the last 60 
or 100 feet. Geologists who have regarded the great work of 
degradation chiefly from this inland point of view, have called 
the level surface down to which the whole land is thus reduced 
by sub-aerial agencies the Base-level of Erosion. Another name 
suggested by American Geologists for it is Peneplain; a word 
which they would define to mean a region of faint relief, the 
penultimate result of long-continued action of denudation on a 
once larger land-mass, whose ultimate result is a base-levelled plain. 
Of course it is to both of the agencies above mentioned, 
acting simultaneously throughout long ages, that we must refer 
the tremendous results that we have forced upon our attention 
as we look around from the top of Ingleborough. We will refer 
to these great plateaux by the shorter term Sea-plain; to dis- 
tinguish them from the River-plains or JBed-plains, of both which 
also we have examples round Ingleborough. 
It is possible that there might be traces of the action which 
formed these sea-plains. Fissures filled by debris of the Poikilitic 
and Jurassic sea were found by Charles Moore in the Carboniferous 
Limestone, near Bristol. 
Why should we not find in cracks and fissures on the top 
of Ingleborough, or of some other parts of our ancient sea-plain, 
the debris washed in by the sea that reduced them to this level? 
