A disk, divided into black and white quarters, used to gauge water clarity by measuring the depth at which it is no longer visible from the surface.
A circular, white or colored disk lowered into a body of water to estimate the clarity of the water by measuring the depth at which it disappears.
An instrument used for measuring the clarity of water, especially seawater. It consists of a circular plate divided into alternating black and white quadrants and attached to a long measuring tape. The plate is lowered into the water, and the depth at which it is no longer visible from the surface is recorded. The Secchi disk is named after its inventor, Italian astronomer Angelo Secchi (1818–1878).
Origin of secchi-disk
- After Pietro Angelo Secchi (1818–1878), Italian astronomer hired to test such a disk
From American Heritage Dictionary of the English Language, 5th Edition
- Secchi + disk