A vessel can be made which, as long as you pour in any liquid, admits it, but, if you once cease pouring, holds no more: the construction is in this manner.
Let A B (fig. 35), be a vessel, the neck of which is
closed by the partition C D. Through the partition insert the tube E F,
reaching nearly to the bottom, and projecting above the partition so as
almost to reach the brim of the vessel ; and let this tube be encircled
by another G H, the top of which is closed by a lid, at a sufficient
interval from the partition and the tube E F to admit of the passage of
water: in A B make an air-hole, K, leading into the body of the vessel.
Now, if we pour liquid into the vessel's neck, it will be found that it
will pass into the body through the tubes G H and E F, the air
retreating through the vent K. But, if we cease pouring, and the neck of
the vessel becomes empty, the air will break the continuity, so that any
liquid in G H will flow down and fall upon the partition; for the
breadth about the tube G H should be considerable, that the water may
fall by its own weight. If more liquid be poured in, the air confined
in the tubes E F and G H will not allow it to pass through, so that it
will run over the brim of the vessel.