264 UNDERGROUND WATERS OF NORTH-WEST YORKSHIRE. 
A gauge board was erected across the Fell Beck just above 
the point where the water commences to sink. This gauge 
had a notch 1 foot wide, and at the time of the experiment 
now to be described the flow was 3^ inches, being equivalent to 
251,856 gallons per 24 hours. The stream, however, was entirely 
absorbed b}^ the hmestone before the main entrance to Gaping 
Glwll was reached, and no water was falling down the main 
shaft. 
Subsequent investigations''' have sho\\n that the water 
sinking in the cracks about 200 feet up Fell Beck from the mouth 
of Gaping GhvH and between these two points flows into the 
cave at the foot of the main hole b}^ way of the parallel shaft 
and the underground waterfall alread}' mentioned. 
Thus the water which sinks in the bed of the beck, and 
that which in wet vvcather flows over the lip of the main hole, 
have a common destination, since they mingle at the foot of 
the shaft. This knowledge simplifies matters considerably, as 
it is rendered unnecessary to test the stream under varying 
conditions of rainfall. 
Two charges of ammonium sulphate, each consisting of 
2 cwt., were put into the dam above the gauge board at 11.30 
a.m. and 2.30 p.m. respective^ on April 28th, 1900, the quanti- 
ties used being comparative^ small on account of the fact that 
all the sj^rings in Clapdale flow into Clapham Lake, which is 
used as a public water supply, and it was therefore necessary 
to avoid the introduction of larger quantities. 
From the time of the introduction of ammonium sulphate, 
samples were collected from Moses' Well (S 7), from a small 
spring (S 13) just above Clapham Beck Head, from Clapdale 
Sike (S 10), and from Clapham Beck Head (S 12), the large 
spring issuing from the foot of the western wall of the gorge 
just above the bridge at the entrance to Ingleborough Cave 
(PI. XXXII. , Fig. 2). 
Only small traces of ammonia were found in the three 
first-mentioned springs, but on the morning of May 3rd a fair 
amount was detected in S 12 ; by noon of the same day this 
* S. W. Cuttriss, Yorkshire Ramblers' Club Journal, Vol. II., Xo. 5, 
1903, pp. 48-51. 
