736 HEPORT — 1900. 



■branches of the Craven Fault with the downthrow to the south. Malham Tarn 

 lies on Silurian, and its overflow sinks in the limestone directly the northern fault 

 is crossed. The draiuage of the area to the west of the Tarn disappears at the 

 Smelt Mill Sink The drainage of the area east of the Tarn is carried off by 

 Gordale Beck along the coarse of which some water sinks into the jointed lime- 

 stone. To these three sinks correspond three principal outlets, the stream at 

 Malham Cove, Aire Head Springs, and the springs at the bottom of Gordale. 



The history of previous investigations is then given. From the centre of 

 Malham Cove a dry limestone gorge runs in a northerly direction to the Tarn. 

 Up to the beginning of this century floodwaters were known to traverse this 

 valley and dLscharge over the Cove. There are several sinks along the hne of 

 this dry valley. Now all the overflow is taken by three sinks south of the Tarn. 



Various efforts have been made to trace the connection between the sinks and 

 outlets. Flushes of water from the Tarn have been shown to affect Aire Head 

 before Malham Cove. Experiments by introducing chaff, bran, magenta, and 

 uranin into the sinks failed to show any traces at the outlets. 



The present investigation was carried out during 1899 by a Committee of 

 Enn-ineers, Chemists, and Geologists, appointed by the Yorkshire Geological 

 and Polytechnic Society. Flushes of water were sent down from the Tarn to the 

 Tarn Water Sinks. Aire Head Springs responded in two hours. With large 

 flushes a rise in Malham Beck was also observed. 



The chemical investigations were as follows : 



Ammonium sulphate was put in below the Malham Tarn Sluice on June 22, 

 and appeared at Aire Head from July 4 to 11. Distinct traces were also found 

 at Malham Cove on the same dates. 



Common salt and fluorescein, put in at the Smelt Mill Sink between June 22 

 and 28, appeared at Malham Cove from July 4 to 11. 



Fluorescein, put in at Tranlands Beck on June 22, appeared at Scalegill Mill 



Ammonium sulphate, put into upper Gordale Beck on August 2G, appeared at 

 the springs below Gordale Scar on September 7. 



Common salt, put into Cawden * Burst ' on September 18, appeared at Mire's 

 Barn from September 23 to 27. , ^.„ „ 



Fluorescein put into the bottom of Grey Gill Cave was not traced. 



A geological investigation of the area showed that the limestone is traversed 

 by two sets°of prominent joints, of wbich the master-joints, which run in a north- 

 west to south-east direction, are very well developed. These master-joints are 

 found to laro-ely determine the flow of the underground waters. 



The direction of these master-joints unites the Smelt Mill Sinks and Malham 

 Cove directly, and that may be taken as the direction of flow. A parallel line 

 from Malham Tarn Sinks would bring the water from them to Grey Gill, a dry 

 valley in the escarpment to the east of Malham Cove. No evidences of moving 

 water were found there. 



To the south of the Mid-Craven Fault the jointing of the limestone is found 

 to be variable; but prominent joints were found bearing in a north-east and south- 

 west direction! If the Tarn water followed these joints on crossing the fault it 

 would traverse a direction almost at right angles to its previous course, and, 

 following the limestone in its bend underneath a synclinal of Yoredale shale, 

 would be likely to reappear at Aire Head Springs, which is the nearest point 

 for xe-emergence on the southern side of the anticlinal. 



The master-joints north of the Mid-Craven Fault would similarly carry the 

 water which sinks into the bed of Gordale Beck south-eastward into the lime- 

 stone, and if, as it nears the fault, it followed a set of joints running at right 

 ano-le's to the previous set, it would come out at the springs at the foot of Gordale 

 Scar which was found to be the case by the chemical tests. Gordale itself turns 

 in this direction from some cause. 



The conclusions of the Committee are : 



1. That Malham Cove Spring discharges the water from Smelt Mill Sink and 



