Nansen Bottle

A Nansen bottle is a classical seawater sampler introduced by Fridtjof Nansen in 1894, the standard tool for depth-discrete sampling before electronic CTDs. A metal tube with valves at both ends is clamped open to a wire and lowered to depth; a brass messenger slid down the wire trips the bottle, which flips over (reverses), closing both valves to seal an uncontaminated sample. Paired reversing mercury thermometers, fixed by the same inversion, recorded in situ temperature, and the protected-versus-unprotected pair gave depth from the pressure effect. The spring-loaded Niskin bottle, introduced by Shale Niskin in 1966, replaced it on rosettes because it needs no inversion and can be non-metallic.