MOVEMENTS OF UNDERGROUND WATERS OF NORTH-WEST YORKSHIRE. 227 



This, together with the failure of methylene blue to put in an appear- 

 ance when used at Grey Wife Sike, as mentioned in the second report of 

 this committee, demonstrates conclusively the superiority of fluorescein 

 for purposes of this nature. 



Long Churn Spring. — This rises on the upper slopes of the fell and 

 sinks on Borrin's Moor at P 42, and after a very short underground 

 course issues at S 57, forming, however, only a very insignificant part of 

 that spring. 



The next series of experiments had for its object the discovery of the 

 source of the bulk of the water at S 57. 



On examining the upper part of Alum Pot Beck it was found that a 

 large part of that stream sank at P 33, and fluorescein introduced here 

 was seen at S 57 within an hour. 



P 26 was the next point of experiment, and by a series of trials with 

 fluorescein it was found that the water flowed underground along a well- 

 marked line of joint to P 43 a. 



This line of joint is well marked both by crevices in the clints and by 

 a line of pot-holes, in some of which the water shows itself. It runs 

 N. 18° W. 



At P 34 a the water falls into another open joint, running N. 25° E., 

 which leads it to S 51, whence it runs over the surface to P 43, again 

 beneath the surface to S 40, and then on to S 42 and P 37, where it again 

 disappears. 



At the time of these experiments the greater part of the water was 

 sinking in the bed of the stream at P 37 a, but a little was flowing on to 

 P 37 near the old limekiln. 



Fluorescein put into the stream just above P 37 a came out at P 38, 

 where it again sank and reappeared half an hour later almost simul- 

 taneously at S 43 and S 44. 



It was then traced to P 39, where it again went underground to issue 

 at Font Green Spring, S 45. 



At P 40 part of this stream sinks (the whole of it in dry weather) to 

 reappear at S 46, and part flows over the surface, the streams when 

 reunited forming Selside Beck, which runs through the village of Selside 

 and on into the River Ribble. 



The above streams occupy a wide valley and would, with the excep- 

 tion of Gill Garth Beck (P 26 to P37), all drain into Selside Beck were 

 they not swallowed into cracks in the limestone. 



There would appear to be two distinct sets of channels below Font 

 Green — a deeper and a more superficial one. 



The water flowing by the deeper channel — viz., that from Alum Pot, 

 Long Churn, and P 41 — reaches the Ribble by way of Footnaw's Hole 

 and Turn Dub, while the shallower set issues on Font Green and joins 

 Selside Beck. 



Many of the underground stream courses are accessible and may be 

 followed for long distances with the aid of short ladders, provided the 

 explorer does not object to getting wet and doing a certain amount of 

 crawling in the less lofty portions. 



It was laid down in the two previous reports of this Committee that 

 as a general rule the flow of undei'ground water in limestone rocks follows 

 the direction of the master joints, and this view has been strikingly con- 

 firmed by several of the experiments which have been carried out during 

 the current year. 



Q2 



