HUGHES : INGLEBOROUGH. 
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unweathered rock on which glacial boulders are perched (see 
Plate XXXIV., Fig. 2). In some cases glacial stride are still 
preserved upon the surface of the rock on which they rest. 
These must not be confounded with the undercut blocks of 
limestone which stand there in their original position owing 
to the removal of the intermediate rock that once extended 
continuously over the whole area (see Fig. 2). The limestone 
weathers along joints, and the corners and edges of the isolated 
blocks are rounded off, as in the case of the grits of Bramham 
Moor or the granites of Cornwall. On the north-west side of 
Ingleborough, above Sleights Pasture, there are many good 
examples of this, showing the manner in which Logan Stones, 
Perched Blocks, and similar phenomena are produced. 
We have seen how, under certain conditions, the sand and 
boulders, hurried along by water, help mechanically to carry 
Fig. 2. 
BLOCKS OF LIMESTONE ISOLATED OWING TO THE WEATIIKRING AWAY OF 
THE SURROUNDING PART OF THE BED. SLEIGHTS PASTURE, N.W. OF 
INGLEBOROUGH. 
away the rock. But there is another ver}^ interesting phenomenon 
to be seen sometimes when flood- water is driven along with 
great velocity over the jointed face of limestone, such as occur 
below Ingleborough Cave or above Gaping Gill. The joints 
and the lines of weakness between two beds are opened out, or 
perhaps a shaley parting removed. The limestone then lies 
in large detached slabs fitted together so closely and so deeply 
that they could not be lifted out by any ordinary operation. 
They rest on concretionary lumps which allow a large body of 
water to be in contact with the lower surface of the slab and in 
communication through the joints with the body of water coming 
down stream. When in flood-time the volume and velocity of 
this is increased, the pressure on the small area of water in the 
joints is multiplied by the hydrostatic paradox over the under 
