OED and definition of "siphon"

[victor steinbok]

One more quick note--there is one exception where atmospheric pressure
/is/ used to initiate the siphoning process without pumping. If the
two columns of liquid are separated by an air bubble, and the terminal
column of liquid is allowed to empty into container, the pressure
differential between the initial container and the bubble may be
sufficient to drag the liquid across the bridge and down into the
terminal container. But this is only the initial action--once the
bubble flows out, it's back to the previously described siphon action.

VS-)

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