THE UNDERGROUND WATERS OF NORTH-WEST YORKSHIRE. 17 
Smelt Mill Water Sink and the Malham Cove outlet is there- 
fore abundantly demonstrated. 
The suddenness of the rise in combined chlorine suggests 
something of the nature of a flushing out of underground 
channels, and it was therefore decided to compare these results 
with the rainfall. 
Mr. Morrison has kindly supplied the record of the Malham 
rainfall over the period covered by the experiments, these results 
are plotted in the diagram (Plate II.) from which it will be seen 
that heavy rainfall shortly preceded the maximum chlorine 
observations. No sample of water appears to have been taken on 
the 3rd of July, so that we are not in a position to say that 
the chlorine figure on this day was not higher even than on the 
4th. The conditions preceding the rainfall were briefly these : — - 
On the 22nd of the month 19,800 gallons of water per 
day were sinking at the Smelt Mill Water Sink (Plate III.), 
as carefully gauged by Mr. Fennell. After this date the water 
sinking would be a diminishing quantity as there was no rainfall 
up to the 27th, then there is a temporary rise in the rainfall 
curve and a further and larger rise on the 30th of June and 
the 1st of July. The waters of Aire Head, Scale Gill Spring, 
and Gordale Beck remained normal throughout the entire series 
of observations, showing that the Smelt Mill Water Sink under 
the conditions investigated is not connected with any of the 
last three outlets. 
Ammonium Sulphate. 
The search for the ammonium sulphate put into the Water 
Sink below the Tarn outlet (Plate V.) was qualitative, being the 
simple addition of Xessler's reagent. Very decided or marked 
results were looked for, and such results were obtained with the 
water from Aire Head from July 4th to 11th. Distinct traces 
of the presence of the ammonium compound were also present 
in the Cove water on July 4th, and for a week after. 
c 
