On the Mississippi River, where constant vigilance is needed because of the rapid shifting of sand-bars, a special sounding nomenclature has come into vogue,[219] which the following terms will illustrate: 5 ft.

= five feet.
6 ft.

= six feet.
9 ft.

= nine feet.
10-1/2 ft.

= a quarter less twain; _i.e._ a quarter of a fathom less than 2.
12 ft.