362 -. Observations on an 
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. Si- 
milar vicissitudes will also take place in the 
siphon; for it wilkrun, so long as its shorter 
leg is in the water, and then stop, until the 
highest point of the bend is again conor by 
the contents of the cup. 
The transition is easily made from ‘Tan- 
talus’s cup to a fountain, which reciprocates 
periodically ; for we have only to suppose a 
secret reservoir to be formed in the bowels of 
a mountain on the principles of this instru- 
ment, and the following appearances will take 
place in the visible well, which receives the 
water from the natural siphon. Ist. 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 conse- 
