Water bottle for collecting seawater samples designed by Alexander Marcet and John Frederick Newman

Alexander Marcet (1770-1822) was a chemist interested in analysis of seawater from different parts of the ocean. He knew that when a simple valved bottle was hauled in, it was almost impossible to keep a steady pull on the line against the motion of the waves and the pitching of the ship. He thought that it was probable that the valves would reopen and every sample would be contaminated by near-surface water. His improvement was to contrive a spring mechanism, whereby a heavy weight kept the valves open until, on striking bottom, the spring closed and held the valves secure whatever the subsequent movement of the line and bottle. His initial design, used by Lieutenant John Franklin on his Arctic expedition aboard HMS Trent in 1818, was found to be too light in construction to be effective.

This bottle is one of Marcet’s subsequently modified, and more robust, instruments. It also features an early version of a ‘messenger release’ system, designed by the instrument maker John Frederick Newman, which enabled samples to be taken mid-water rather than from the sea floor. The flap-valves of Marcet’s original design were replaced with ground conical plugs, sliding on a central guide held open by a hinged lever, counterpoised by a suspended weight. If the bottle was to sample at the bottom, then the release of the counterpoise as it struck the sea bed allowed the valves to drop shut under their own weight. To sample in mid-water, a heavy weight was sent down the line, and this overcame the pull of the counterpoise so that the valves closed.

Alexander Marcet (1770-1822) was a chemist interested in analysis of seawater from different parts of the ocean. He knew that when a simple valved bottle was hauled in, it was almost impossible to keep a steady pull on the line against the motion of the waves and the pitching of the ship. He thought that it was probable that the valves would reopen and every sample would be contaminated by near-surface water. His improvement was to contrive a spring mechanism, whereby a heavy weight kept the valves open until, on striking bottom, the spring closed and held the valves secure whatever the subsequent movement of the line and bottle. His initial design, used by Lieutenant John Franklin on his Arctic expedition aboard HMS Trent in 1818, was found to be too light in construction to be effective.

This bottle is one of Marcet’s subsequently modified, and more robust, instruments. It also features an early version of a ‘messenger release’ system, designed by the instrument maker John Frederick Newman, which enabled samples to be taken mid-water rather than from the sea floor. The flap-valves of Marcet’s original design were replaced with ground conical plugs, sliding on a central guide held open by a hinged lever, counterpoised by a suspended weight. If the bottle was to sample at the bottom, then the release of the counterpoise as it struck the sea bed allowed the valves to drop shut under their own weight. To sample in mid-water, a heavy weight was sent down the line, and this overcame the pull of the counterpoise so that the valves closed.