Secchi disk
Disco Secchi
- Date
- 1865 · confidence high
- Place
- Tyrrhenian Sea, Italy
- Credited to
- Angelo Secchi
- Field
- Knowledge & symbols
What it is
A 30 cm white disc lowered slowly into water to measure its transparency: the depth at which it disappears from view is the "Secchi depth". It remains the simplest and most widely used method for assessing water turbidity.
Devised during an expedition aboard the papal steamer Immacolata Concezione.
What it led to
- A standard oceanographic and limnological method for measuring turbidity
- Black-and-white chequered discs used as calibration markers in crash tests