RECIPROCATING SPRINGS. 
283 
sequel, are of this kind ; and Pliny’s well, near Coma, ap- 
pears to possess the same character from his description of it. 8th 
The fluctuations of an ebbing and flowing well, which is fed by 
a siphon, m* 11 remain invariable, so long as the stream, that 
falls into the subterranean reservoir continues to be uniform. 
But these external and visible operations of the well, are so far 
under the influence of the current last mentioned, that they The fluctua- 
will evidently suffer a temporary suspension, so often as ti . 0RS of ’an eb . 
the inflnx into the concealed cistern, amounts to a certain h!”^elfvvillb e 
quantity in a certain time j for the siphon is but a secondary fewcrthe great 
agent in producing the phenomena of reciprocation, its husi- & c tlie Sllpi> * y 
ness being to empty the subterranean basin, so often as it is 
replenished. Now the time of filling this magazine of water will 
be the shortest, when the influx into it is most abundant, and 
the contrary j consequently an increased discharge into the sub- 
terranean reservoir, 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 well will assume the character of a common fountain 
under these circumstances. 
I have now explained the principles, on which the com- T{ie springs 
mon theory of reciprocating springs is founded ; and the neces- before men- 
sary consequences of the theory are stated in the eight pre- expl^ned by 5 
ceding propositions. This has been done, to shew with what the siphons: 
ease a natural apparatus on the construction of Tantalus’s cup 
elucidates the appearances, which have been ascribed by wri- 
ters to the fountains of Doiona, 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 pro- 
nounce 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 Plinys, as well as the history of the 
inconstant brook in Westphalia, disposed me to admit the com- 
mon theory, and to imagine it to be equally applicable to reci- 
procating fountains in general j until an instance occurred to 
my notice, which pioved that, fluctuating fountains do not uni- 
versally exhibit the periodical operations which are described by 
the 
