RECIPROCATING SPRINGS. 
181 
the boisterous brook. This is an appellation which it 
deserves for after flowing twenty-four hours, it ceases for 
six hours \ at the end of which period -it returns with a 
great noise, and force sufficient to turn three mills, situated 
near its visible source. The operations of this fountain are 
differently described in the Philosophical Transactions, where 
it is said to lose itselftwicein twenty-four hours -5 coming always 
after six hours back again. Lowthorp’s Abridgment Voi.II.p.306. 
ment, Vol. II. Page 305. 
The prevailing opinion, respecting the nature of reciprocating 
fountains appears to be derived from the three preceding instances j 
at least I am not acquainted with any other topographical account, 
which can be said to favour the notion oq rational, or even on pro- 
bable principles. This theory may be found in many popular works 
on natural philosophy ,• and it is easily explained by the hydrau- 
lic machine called Tantalus’s cup. This instrument consists 
of a vessel furnished with a siphon, which may be attached 
to it in different ways. To avoid the necessity of a diagram, 
we will suppose the bottom of the vessel to be perforated, 
and the longer leg of the siphon to pass through the hole, 
being firmly cemented in a position, which places the highest 
point of the bend within the vessel, and half an inch or an 
inch below the brim, and at the same time keeps the open or 
lower end of the shorter leg at a small distance from the cup's 
bottom. Water flows through a tube in an uniform stream 
into the cup 5 where it is collected for want of egress, and en- 
tering the siphon at the open end of the shorter leg, it rises 
gradually to the bend or highest point. The subsequent rise 
of the water in the cup, forces the column in the ascending 
Teg of the siphon, to passover into the descending or longer 
branch j upon which this instrument begins to act, not in 
the manner of a simple tube, but in its proper character. 
Now the draft of the siphon is made to exceed the opposite 
stream or supply of water j in consequence of which contri- 
vance the cup is emptied again sooner or later ; at this moment 
the action of the siphon is suspended, until the cup is replenished 
by the constant current. In this manner the water will be seen 
rising and falling alternately in the cup, which will be full and 
empty, or nearly so, by turns. Similar vicissitudes will also 
take place in the siphon ) for it will run so long as its shorter 
leg 
General 
theory of a 
siphon, like 
that in the cup 
of Tantalus. 
Description 
of the appa- 
ratus so called* 
