12 
THE UNDEKCxROUXD WATERS OF NORTH-WEST YORKSHIRE. 
The time chosen was particularly favourable for carrying 
out experiments on underground water, as there had been practi- 
cally no rainfall for the previous three weeks. A little rain 
had fallen in the early hours of the 22nd, and probably affected 
Aire Head at 10.15 a.m. ; it caused, however, a very slight 
increase in the yield. This increase was not shown at all in 
Malham Beck. Reference to the diagram (Plate I.) shows 
that the effect of a steady flow of water at the rate of 
nearly 700,000 gallons a day, started through the sluice at the 
Tarn at 10.15 a.m. and allowed to continue until 1 p.m., 
began to exhibit itself at Aire Head at 12.15, showing a 
steady rise until 2.45 when the first supply was overtaken 
by the much greater volume of water, which was let off 
from the Tarn at 1 p.m. During the whole day, as shown on 
the diagram, the gauging at Malham Beck near the Cove 
remained constant. The great flush of water let off from the 
Tarn for 45 minutes affected tlie Aire Head stream for three 
hours. From this we learn that the stream bed and outlet were 
insufficient to deal w4th this large volume of water, and that it 
w^as backed up. No doubt if the flush had continued for a longer 
period, or had been greater in volume, the strata would have 
got charged with w^ater to such a height as to cause an overflow 
into the Malham Beck through some fissures or over some under- 
ground sill, causing it to rise as noticed when Mr. Morrison and 
Mr. Tate experimented in 1879. 
We are unable to give any information as to the area 
drained by the tributaries of the Aire above Kirkby Malham 
without further water-gaugings, which should be taken over a 
period of many weeks. 
The following, however, may be arrived at from the above 
experiments, viz. : — That the area drained by the stream at Aire 
Head is probably distinct from the area drained by the stream 
from Malham Cove or Malham Beck, because the flow at Malham 
Beck was constant the whole time that the experiments were 
carried on ; but this is not proven, as the gaugings were not 
