USS Octorara (1862-1866) Watercolor by Alex Stuart. Courtesy of the Navy Art Collection, Washington, DC. U.S. Naval Historical Center Photograph. http://www.history.navy.mil/photos/sh-usn/usnsh-o/octorara.htm ...
Found on
http://en.wikipedia.org/wiki/Secchi_depth
A relatively crude measurement of the turbidity (cloudiness) of surface water. The depth at which a Secchi Disc (Disk), which is about 10-12 inches in diameter and on which is a black and white pattern, can no longer be seen.
Found on
http://www.encyclo.co.uk/local/21804
No exact match found.
