CATARACTS, AND INUNDATIONS. 87 



which may be attached to it in different ways. To avoid the 

 necessity of a diagram, \ve 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 be- 

 low 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 ; where it 

 is collected for want of egress, and 'entering 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 leg of the siphon, to pass over into the 

 descending or longer branch ; upon which this instrument begins to 

 art, not in the manner of a simple tnbe, but in its proper character. 

 Now the draft of the siphon is made to exceed the opposite stream 

 or supply of water; in consequence of which contrivance 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 is in the water, and then stop, until 

 the highest point of the bend is again covered by the contents of 

 the cup. 



The transition is easily made from Tantalus's cup to a fountain, 

 which reciprocates periodically; for we have only to suppose a se- 

 cret reservoir to be formed in the bowels of a mountain on the prin- 

 ciples of this instrument, and the following appearances will 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. This abundant Influx into the external well will make 

 it rise; in consequence of which the efflux will continue to increase 

 at the outlet, so long as the water coulinues to accumulate in the 

 visible basin. 3d. Now the discharge from the outlet, which be- 

 comes more copious every moment, being contrary to the influx '* 



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