348 REPORT— 1900. 



there existed any connection, between Gaping Ghyll and the smaller 

 springs in Clapdale, 10 cwt. of common salt was put into the waters 

 of Gaping Ghyll on June 4, and a further 10 cwt. on June 5, samples 

 of the water from each of the springs being taken several times a day 

 until June 25. 



One pound of fluorescein in alkaline solution was introduced into the 

 stream flowing through Ingleborough Cave on June 8 at 10 P.M., at the 

 point where the water plunges down a hole in the floor of the cave, and 

 marked ' Abyss ' in the 6-inch Ordnance map. 



Five cwt. of ammonium sulphate was introduced into a sink on The 

 Allotment about 500 yards N.E. of Long Kin East on June 9, at 3 p.m. ; 

 and at 3.15 p.m. on the same day 1 lb. of fluorescein in alkaline solution 

 was poured into the stream which flows past the shooting-box on The 

 Allotment and sinks near the Bench Mark 1320"1. 



The fluorescein introduced into the abyss came out at Clapham Beck 

 Head, and possibly at Moses "Well and other springs in Clapdale, but this 

 point requires further investigation, the evidence being as yet somewhat 

 unsatisfactory. 



The salt from Gaping Ghyll appeared at Clapham Beck Head on June 

 15, 16, 17, 18, 19, 20, and 21, being at its maximum on June 18, but not 

 at any of the other springs. 



The ammonium sulphate put into the sink on The Allotment appeared 

 at Austwick Beck Head on June 22, the other springs in the neighbour- 

 hood being unafiected on that day ; but on the 24th and 25th there were 

 slight increases in the amount of ammonia in two small springs in Clap- 

 dale, viz. the small spring below Clapdale Farm, and Cat Hole Sike. As 

 one of these streams is close to the farmyard, and the other was at the 

 time nearly dry and flowing through pasture-land, no importance is 

 attached to these slight increases. 



Of the fluorescein put in below the shooting-box no trace has since 

 been found, and the same is the case with ^ lb. of methylene blue intro- 

 duced into Grey Wife Sike, above Newby Cote. 



Several most interesting problems still await solution in this area, one 

 of them being the relations of the Silurian floor, which underlies the 

 Carboniferous Limestone of the plateau, to the flow of undergi'ound water. 

 The two sinks Gaping Ghyll and Long Kin East are only about 1,300 

 yards apart, and yet the waters of the one take a direction quite distinct 

 from those of the other, and eventually emerge in a separate valley, the 

 distance between the springs being 1^ miles, the great mass of Carboni- 

 ferous Limestone known as Norber, a hill upwards of 1,300 feet in height, 

 lying between the two valleys. 



In Crummack Dale it is seen that the Silurian rocks form a ridge 

 running in an approximately N.W. and S.E. direction, and unconformably 

 overlain by the Carboniferous Limestone. 



If this line be continued it separates the Gaping Ghyll to Clapham 

 Beck Head flow from that of Long Kin East to Austwick Beck Head. 



Thus it appears that this ridge of Silurian rocks forms an underground 

 water-parting, which the Committee hopes to be able to trace further 

 across the area. 



The magnitude of this undei'taking will be to some extent realised 

 when it is stated that upwards of 400 samples of water have been tested 

 for common salt, ammonia, and fluorescein, making in all upwards of 

 1,200 tests. 



