132 
RECIPROCATING SPRINGS. 
leg is in the water, and ihen stop, until the highest point of 
the bend is again covered by the contents of the cup. 
Application of The transition is easily made from Tantalus’s cup to a foun- 
the cs^toex- ta * n > w ^ch reciprocates periodically ; for we have only to 
plain t e phe* suppose a secret reservoir to be formed in the bowels of a 
liable springs" mounta ' n on principles of ..his instrument, and the following 
appearances wili take place in the visible well, which receives 
the water from the natural siphon. 1st. So soon as the surface 
of the pool in the subterranean reservoir, rises above the bend of 
the siphon, this canal will begin to act ; and its discharge will be 
greater at that moment than at any, other period ; because the 
power of a siphon is greatest, when the distance, betwixt the 
bend and the surface of the water in the basin, is least. 2d. 
Tin* abundant influx into :e external well wili make it rise ; 
in consequence of wh eh ne efflux wili continue to increase at 
the o ulet, so long as th water continues 10 accumulate in the 
visible basin. 3d Now the discharge from die outlet, which 
becomes more copious every moment, being contrary to the 
influx from the siphon, which grows gradually weaker, the 
surface of the well will cease to rise so ; >on as these opposite 
powers are equal in their effects ; and thi flow wili be at the 
full in this instant. 4th The well cannot remain stationary, for 
any length of time, at its highest elevation j because the vigor 
of the siphon being perpetually on the decline, all the water 
discharged by it will run 'off through rh; outlet, together with 
part of that, which had been previous v accumula'en in the 
visible fountain, during the time of th* flow 5th. Hence it 
is evident that the well will begin to subside, the moment it 
becomes stationary } after which, it will persevere in a rei ro* 
grade morion, until the siphon shall have emptied the subterra- 
nean reservoir. 6th. If no veins of water discharge them- 
selves into the visible basin, beside* the siphon which runs 
Difference be- periodically, the spring is called an intermitting fountain, 
tween inter- The Bolderborn is of this kind, for it remains dry while the 
ciprocaflnp'^ 6 secret reservoir is filling, and flows while the siphon is in ac* 
springs. tion. But if the spring receive- other supplies in addition 
* to the intermitting current, it is called a reciprocating 
fountain j because the stream that issues from the outlet of the 
visible basin is permanent, though ir varies in quantity $ on this 
account the well ebbs and flows alternately, but never runs it- 
self dry. All the fountains., which will be mentioned in the 
