12. A Vessel from which the contents flow when filled to a certain height.

There are some vessels which emit no stream unless they are filled; but when filled discharge all the liquid they contain. They are made as follows: Let A B C D (fig. 12) be a vessel open at the top, and through its bottom pass a tube, either an inclosed diabetes as E F G, or a bent siphon G H K. When the vessel A B C D is filled, and the water runs over, a discharge will begin through the diabetes, and continue till the vessel is empty, if the interior opening of the diabetes is so near the bottom of the vessel as only to leave a passage for the water.