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![Figure 1 ship4454.jpg Figure 1](/sites/default/files/styles/max_1300x1300/https/s3.amazonaws.com/s3-east-testmedia-noaa.woc.noaa.gov/dam/Photos/legacy/pl23_ship4454.jpg?itok=gYSLPfUP)
Description
Figure 1. A plastic Secchi disk of recent origin. This disk islowered in the water until it disappears from sight. The depth at which it disappears is a measure of the water's transparency. Father AngeloSecchi devised this method in 1865 and tested it aboard the Vatican vessel IMMACOLATA CONCEZIONE. Several models were tested of different colors. (Image credit: Oceanographic Museum of Monaco | Y. Berard)