Messenger weight, 7 of 12
Date1940-2000
Object number00055909
NameWeight
Mediummetal
DimensionsEstimated acquisition size: 170 × 400 mm, 5 kg
ClassificationsTools and equipment
Credit LineAustralian National Maritime Museum Collection Gift from Defence Science and Technology Group
DescriptionSeven of twelve cylindrical metal weights stored inside messenger bag.HistoryMessenger weights are the mechanism used to begin the sample capturing process whilst on board vessels and conducting research. Water sampling bottles are deployed overboard, valves open on either end of the bottles, connected via a winch line. These are lowered to the desired depth in the ocean where measurements are to be recorded. This begins by the messenger weights released to slide down the winch line which disengages the top of the sampling bottle from the line upon impact. The bottle is then able to flip over which causes the valves to close, thus trapping the water inside. If there are multiple water sampling bottles attached to the same winch line at various lengths then differing depth samples are able to be recorded from one deployment. After the messenger weight reverses the first sampler along the line, it triggers the next messenger weight to release down the line beginning the process of capturing a second sample. This process can keep repeating down the line until all connected samplers have been flipped and trap their water sample. Any attached sensors can record their data at depth as well.SignificanceMessenger weights are a key mechanistic part of sample collection for oceanographic research in the 19th and 20th century. They not only triggered water sampling collection but more and more data sensors that were created over time. Reversing thermometers used to be commonly attached in tandem with samplers that were activated when flipped to capture their water sample. This meant that the thermometer took a snapshot reading of the water temperature at the depth the sampler had been deployed down to.