Ebbing and Flowing Well. 865 
servoir, will diminish the intervals of the 
siphon’s inactivity, and prolong the periods 
of its action. It follows from these premises, 
that when the influx becomes equal to the 
feeblest effort of the siphon, the quantity of 
water thrown into the concealed basin, will 
exactly counterbalance the quantity which is 
drawn off by the crooked canal; and the 
external weil will assume the character of a 
common fountain under these circumstances. 
I have now explained the principles, on 
which the common theory of reciprocating 
springs is founded; and the necessary conse- 
quences of the theory are stated in the eight 
preceding propositions. This has been done, 
to shew with what ease a natural apparatus on 
the construction of 'Tantalus’s cup elucidates 
the appearances, which have been ascribed by 
writers to the fountains of Dodona, Coma, 
and Paderborn. The operations of these 
springs are happily illustrated by the instru- 
ment in question; on which account I do not 
hesitate to pronounce the theory to be a good 
one, so far as it relates to these fountains 
alone; provided they are faithfully described. 
The simplicity of the preceding explanation 
and its coincidence, with the narratives of the 
two Pliny’s, as well as the history of the in- 
constant brook in.Westphalia, disposed me to 
