Ebbing and Flowing Well. 361 
bable principles. This theory may be found 
in many popular works on natural philosophy ; 
and it is easily explained by the hydraulic 
machine called Tantalus’s Cup. This instru- 
ment consists of a vessel furnished with a 
siphon, which may be attached to it in differ- 
ent ways. To avoid the necessity of a dia- 
gram, 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 ina 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; 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 cor 
lumn in the ascending leg of the siphon, to 
pass over into the descending or longer 
branch; 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; in consequence 
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