THE UNDERGROUND WATERS OF NORTH-WEST YORKSHIRE. 29 
continuity is remarkable. It is possible to select one at the 
north-westerly edge of the plateau which bears directly for the 
Tarn "Water Sinks, and to follow it almost without interruption 
to the crags overlooking Grey Gill. Cross-joints run nearly at 
right angles to these, but any single one can rarely be traced 
for more than four or five yards, though its main direction may 
sometimes be continued e7i echelon by other joints. In some 
places a third set of joints inclined about 35° to the master-joints 
may be observed. 
In the course of this investigation it was ascertained that the 
cave at the head of Grey Gill (Plate YII.) was exactly in the 
line of this section, which fact forms an interesting coincidence. 
This cave bears 340° mag. (the equivalent of the bearing of the 
Water Sinks joints, viz., 1G0° before mentioned), and is obviously 
merely an enlarged master-joint. It is well to state here that 
the cave slopes downward from the entrance towards the !N'.W. 
As to the connection between the joints and the flow of 
water complete proof cannot in all cases be expected, but the 
facts now brought to light seem to justify the inference that 
they have a determining influence, and several flows may now 
be considered seriatim. 
1. Smelt Mill Sink to Malham Cove. 
The route from point to point here so closely approximates 
to the direction of master-jointing that it may, it is considered, 
be taken as fairly certain that the water is transmitted directly 
through a series of enlarged master-joints. 
2. GoRDALE Beck to Gordale Springs. 
These are taken out of their geographical order of succession 
because much light was thrown by the behaviour of the water 
in this instance upon the very difficult case of the Tarn to Aire 
Head flow. 
It was not until this investigation had directed attention to 
the problems of underground saturation-levels that it was more 
