358 Observations on an 
“to suppose, that the subterranean veins of 
“the fountain have a certain capacity ; and 
“that while they are recruiting their ex- 
*“ hausted stores, the stream is small and 
“languid; but becomes stronger and more 
«abundant, when these reservoirs are reple- 
“ nished? Or is there a secret and unknown 
“contrivance of a stop acting on the prin- 
“ciple of a balance; which accelerates the 
“efflux of the fountain while it empties itself, 
and diminishes the current, while it is 
“ filling ?”’ 
The two last suppositions are’ obscurely 
expressed in the original; the latter of them 
however seems to have suggested the hypo- 
thesis of a rocking stone; which acting on 
the principle of a valve, alternately opens 
and shuts the out-let of the spring; and my 
translation is made to favour this conjecture. 
The elder Pliny also mentions the same foun- 
tain, and ascribes to it a very remarkable and 
unaccountable difference ; for he asserts, that it 
ebbs and flows regularly in the space of an 
hour. Hist. Nat. Lib. IL. Cap. etii.. We are 
surprised to find the uncle and nephew, both 
intelligent and observing men, vary so widely 
in the statement of an obvious fact. ‘Their 
disagreement however does not contradict the 
regularity of the spring’s operations ; which is 
