864 Observations on an 
7th. But if the spring receives other supplies 
in addition to the intermitting current, it is 
called a RECIPROCATING fountain; because 
the stream that issues from the outlet of the 
visible basin is permanent, though it varies in 
quantity ; on this account the well ebbs and 
flows alternately, but never runs itself dry. 
All the fountains, which will be mentioned in 
the sequel, are of this kind; and Pliny’s well, 
near Coma, appears to possess the same cha- 
racter from his description of it. 6th. The 
fluctuations of an ebbing and flowing well, 
which is fed by a siphon, will remain invari- 
able, so long as the stream, that falls into the 
subterranean reservoir continues to be uni- 
form. But these external and visible opera- 
tions of the well, are so far under the mflu- 
ence of the current last mentioned, that they 
will evidently suffer a temporary suspension, 
so often as the influx into the concealed cistern 
amounts to a certain quantity’in a certain 
time ; for the siphon is but a secondary agent 
in producing the phenomena of ‘reciprocation, 
its business 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, consequently an 
increased discharge into the subterranean re- 
