«ig Chaar 
101 
beds below would go faster, and the lower rocks would soon begin 
to waste away into a gradually-deepening depression, until they sank 
far below the point reached by the limestone escarpment. In this 
case it has to be remembered, of course, that we are dealing with 
the outcrop, running transverse to the general course of the river, 
of a soft stratum occurring between two of a much more durable 
nature, and one that wastes faster than the rate at which the river 
itself erodes the harder beds above it and below. 
Thus it was, I believe, that the head waters of the Petteril were 
cut off, somewhere out between Penruddock and Mell Fell. The 
Petteril went on deepening and widening its channel here until 
the unequal waste of the surface formed by the soft rocks 
about Dacre developed a channel all along the line where 
these same soft rocks cropped out, that is to say, along 
a zone ranging transversely to the general direction of the river 
valley. Eventually the Petteril was cut in two by this unequal 
lowering of the surface it traversed, the water draining down from 
about Gowbarrow Fell being turned into the new channel that 
now contains Dacre Beck; while the remaining moiety of the 
Petteril had to make a fresh start as best it could, with such 
drainage as gathers about Motherby and Penruddock. 
The same kind of thing happened near Plumpton. The Petteril 
once flowed straight away from the Carboniferous area across what 
is now the escarpment of the Penrith Sandstone, instead of turning 
to the north as it does now. But this escarpment consists of an 
upper layer of hard and durable beds of sandstone, which overlies 
a lower series of beds of a much more perishable character. A 
surface consisting of beds belonging to the whole series would 
therefore naturally tend to waste to lower levels at a faster rate 
where the soft beds cropped out than where they were hard. The 
strike of these beds is here north and south, with an easterly dip. 
Consequently, in the general waste of the strata, there is a 
tendency to a general lowering of the surface in a north and south 
direction, along the outcrop of the softer beds ; while, on the other 
hand, the harder top beds continue all through in the form of an 
escarpment, which is receding towards the east. The hard beds 
