UNDERGROUND WATERS OF NORTH-WEST YORKSHIRE. 
281 
In this older and deeper valley, then, was the original outlet 
of the waters of Alum Pot. This outlet was during the glacial 
period completeh' stopped up with boulder-clay so that when 
tlie flow of water was resumed it had to foice a new passage 
through the boulder-clay. viz.. Turn Dub. which happened 
to be on the opposite side of the present river course. The 
pressure necessary to re-open t]ie passage is not far to seek, 
since if Footnaw's Hole and Turn Dub were stopped up the 
water in Alum Pot would rise to the surface, giving a SCHJ-foot 
head of water. 
This series of observations is of ])articular interest, since 
if the above is the correct explanation it proves that Alum Pot 
and possibly also Long Churn are of pre-glacial origin. 
A series of small springs rises beneath the drift and peat 
near the wall at the north end of \Vhit-a-({reen. These run 
together and form a small stream which sinks at P 34. a small 
pot hole amongst long grass. Fluorescein was introduced here 
and reappeared in half an hour at a small opening some 1(K) 
yards to the south of P 34 : here the stream can be traced on 
the surface for 20 yards, when it again sinks. 
The fluorescein was i)ut into P 34 at 4 p.m. and was traced 
the following day at S 52 ; then overground to P 35. where it 
again sank, to rea])pear at S 49 : thence it flowed to P 36, and 
so underground to S 50, finally sinking at P 41. 
The fluorescein sinking at P 41 did not affect any of the 
springs on Font Green, but was again seen in Footnaw's Hole. 
This water must, therefore, go by a deep course, and eventu- 
ally join the underground flow from Alum Pot to Turn Dub. 
I'ia Footnaw's Hole. 
Passing northwards the next water sink encountered is 
that at the Washfold (P 52), on Bent Hill Rig, Park Fell. This 
receives the waters of Washfold Spring and Old Fold Spring, 
the latter having been diverted to this x:)oint. 
Here half a pound of fluorescein was put into the sink at 
2.15 p.m. on April 4th. 1903. 
This had almost disappeared at 6.15 p.m. when a second 
half-pound was introduced, being arranged so as to flow in 
slowly and keep up the supply for a considerable time. The 
