UNDERGROUND WATERS OF NORTH-WEST YORKSHIRE. 265 
liad increased very considerabl}', but there was a considerable 
diminution in the evening. Froin this date until May 6th 
ammonia was present in diminishing quantity, and on tlie 
evening of that day only a trace remained. 
This result fully proved the direct connection of Gaping 
Ghyll with the spring at Clapham Beck Head. The Avater took 
five clear days to pass along its underground course over the 
mile that intervenes between these points. 
There being some doubt as to whether any of the other 
springs were affected by the ammonium sulphate put into 
Gaping Ghyll, it was decided to perform another test witli 
common salt, as the quantity of this substance in the waters 
of the springs was not so liable to be affected by natural causes. 
Accordingh' half a ton of salt was introduced into the 
waters of Gajiing Ghyll on June 4th, 1900, and another half 
ton on June 5th, samples of water being taken from all the 
important sj^rings in Clapdale several times a day until June 25th. 
The salt from Gaj)ing Ghyll apjoeared at Clapham Beck 
Head on June 15t]i. 16th. 17th, 18th, 19th. 20th, 21st, being at 
its maximum on June 18th. thus taking eleven days for its 
first appearance and fourteen days to attain a maximum 
[PI. XXV. j. 
The difference in time taken by the tests in tlie April and 
June experiments to travel from Gaping Ghyll to Clapham Beck 
Head is of interest. Unfortunately there is no rain gauge at 
Clapham. but by the kindness of Mr. Walter Morrison, of 
Malham Tarn. Mr. Thos. Coulthard has supplied the register 
of rainfall at that place for the months of April, May, and 
June. 1900. This shows that there was a decidedly iieavier 
rainfall in April than in May. that for April being 3-88 inches, 
whilst from May 4th to June 4th only 2 09 inches fell. It 
would appear therefore that the time of flow is much longer 
after a period of diminished rainfall. 
None of the other springs were affected in the slightest 
degree, proving that the small increases in the quantity of 
ammonia carried by these minor streams during the previous 
experiments were not due to the ammonium sulphate intro- 
duced at Gaping Ghyll. 
