THE UXDERGROUXD WATERS OF XORTH-WEST YORKSHIRE. 33 
early outlets. This arrangement would subsist until the point 
of final absorption had receded from the direct line of the 
master-joints running down to the Cove (that is out of the 
Watlowes), and to a spot from which master-joints would lead 
the water eastward of the Cove ; and so on until the water 
was eventually turned towards Grey Gill. 
Upon this supposition we may now consider the probable 
subsequent course of events. A great spring would be likely to 
emerge in Grey Gill and j^roduce a stream flowing down the dry 
channel w hich runs to Gordale Bridge ; but it is well to remark 
here that the character of the upper part of Grey Gill gorge 
and of the country to the north rather favours the view that 
a surface stream (though of smaller volume than that necessary 
to account for the lower part of the gorge) descended here. 
From the level of the cave downwards the floor of Grey 
Gill is composed of loose l^locks of limestone intermingled with 
tufa (the latter indicating plainly that water flowed in a surface 
stream), and no attempts on the part of the Committee to get 
through or to probe to live rock were successful. Attempts 
were repeatedly made to reach the rock, as inhabitants of the 
district testified that in normal seasons a sound of running 
water could be heard, and it was considered that the ]\Ialham 
Tarn water was probably passing here on its way to Aire Head. 
The Tarn stream was twice flushed for the purpose of listening 
both in Grey Gill Cave and the screes below, but no water 
could be heard running then. Fluorescein Avas introduced into 
the bottom of the cave in August, 1899, and washed down 
with 100 gallons of water, but no trace of it has since been 
found. 
Grey Gill changes rather abruptly from its gorge-like character 
Avhere the Mid Craven Fault comes across near Cawden Flats 
Barn, and this fault juxtaposes to the great mass of pure white 
limestone of the plateau the region of "reef-knolls," consisting 
of dark flaggy limestones or shales enclosing great dome-like 
masses of highly fossiliferous limestone, of which Cawden is a 
good example. 
D 
