THE UNDERGROUND WATERS OF NORTH-WEST YORKSHIRE. 35 
The last two readings were taken at the weir about 200 
yards south of Aire Head, and were probably unajffected by 
a small unmapped fault crossing the Aire near the foot of the 
mill dam which had distuibed the joints in the preceding cases. 
Joints bearing in the same direction as these two master-joints 
would connect Aire Head with Grey Gill. 
It appeared to the Committee a fact of some significance 
that a " burst," of great volume and sufficient hydrostatic head 
to propel the water to a height of several feet, breaks out every 
few years at a point on Cawden, exactly on the line between 
Grey Gill and Aire Head. A trial made in September, 1899, 
however, just as the drought broke up, resulted in the discharge 
of the re-agent not at Aire Head but in a small spring at 
Mire's Barn which lies to the north-east on the direct line from 
Aire Head to Cawden " Burst." 
The crossing of the two flows. Smelt Mill to Malham Cove- 
Malham Beck and Tarn Water Sinks to Aire Head Springs, with- 
out any intermingling presents no difficulty. The intercrossing 
cannot take place above Malham Cove, for no impervious stratum 
exists in the Carboniferous Limestone of the plateau to keep 
the two layers of underground water apart : it must take place 
where Malham Beck crosses a syncline of Bowland Shales just 
below the village of Malham. It will be seen from the section 
appended to the map (Plate XII.) that Aire Head Springs 
emerge from beneath the southern edge of these shales. 
Fluorescein put into Tranland's Beck, by the first flood-gate 
above the bridge at the foot of Kirkby Top, re-appeared in 
a spring at Scale Gill Mill. This again is consistent with the 
general direction of master-joints in the vicinity, but there are 
no joint exposures at the particular spots. 
The late Mr. Tate considered that the Smelt Mill Sike could 
not feed Malham Cove Spring because (a) the volume of the 
former was inadequate, being only about ^r^th that of the Cove 
stream, and (b) the quality of the water was difierent. Thus : — 
SMELT MILL. MALHAM COVE. . 
Total Hardness ... 13-1 lOS 
