366 Observations on an 
admit the common theory, and to imagine it 
to be equally applicable to reciprocating foun- 
tains in general; until an instance occurred 
to my notice, which proved that, fluctuating 
fountains do not universally exhibit the perio- 
dical operations which are described by the 
writers. already quoted. I made a visit to 
Giggleswick Well in the autumn of 1796; 
which taught me to value this once favourite 
theory not so highly, and in particular to dis- 
pute the universality of its application. The 
causes of these doubts will be easily perceived 
from the following description of the well and 
its operations. . 
This spring lies at the foot of Giggleswick 
Scar, which is a hill of limestone in the 
West Riding of Yorkshire. 'The water dis- 
charged by it, falls immediately into a stone 
trough; in the front of which are. two holes 
near the bottom; these are the outlets of two 
streams, that flow constantly from the arti- 
ficial cistern. An oblong notch is also cut in 
the same side of the trough; which extends 
from the brim of it, nearly to the level of the 
two holes already mentioned. 'This aperture 
is intended to shew the fluctuations of the 
well: for the water subsides in it, when the 
stream issuing from the rock becomes lan- 
guid; on the contrary the surface of the 
