Deep Sea Thermometer
notes: label: Description
content: Russian reversible deep sea thermometer marked "No. 2894."
label: Description
content: Scientists have been aware since the 17th century of the importance of the oceans in influencing climate, but for obvious reasons collecting the relevant data has not been easy. It has been difficult enough, and expensive, for governments to send out oceanographic expeditions to investigate the physical properties of the surface waters of the ocean, but it is far harder to learn about what goes on in the depths, often miles down. These deep masses of water, at temperatures barely above freezing, circulate slowly, transporting equatorial warmth to the polar seas. Differences of small fractions of a degree can be highly significant. But how do you take a reading of a thermometer hundreds of fathoms down?
label: Description
content: Instrument makers have devised a number of ingenious solutions to this problem; this instrument embodies several of them in a combination that was standard from about 1890 until 1970, when it was finally superseded by modern electronic instruments. First, to eliminate the effect of the immense pressure of the water on the bulb of the thermometer, it was encased in a strong external glass tube. Then, to preserve the reading recorded at the desired depth, the thermometer is designed so that when turned upside-down, the mercury column separates at a defined point. After this, it is no longer affected by temperature changes around it, so, once it has been hauled up from the depths (a process that could take hours), it can be read at leisure from the inverted scale. When turned upright again, the mercury column reconnects, and the thermometer is ready for another reading.
label: Description
content: This reversing principle was introduced by the London firm Negretti and Zambra, makers of optical and meteorological instruments, in 1874. The thermometer would be mounted in a special frame attached to the sounding line, perhaps with others at suitable intervals, and lowered to the desired depth. Then a “messenger” weight was slid down the line to release the reversing mechanism that turns the thermometer over. It also released another messenger below the thermometer, which in turn slid down to the next thermometer in the series, and so on. Attached to each reversing frame, in addition to the thermometer, was usually mounted a “Nansen bottle,” a special container that closes when reversed, securing a sample of the water at that depth for analysis.
label: Description
content: Description: Outer cylindrical glass tube encloses thermometer proper. The bulb of the thermometer is surrounded by mercury in the outer tube, confined to the end by a cork. The scale extends from [-]2 at the top to 30 near the bottom, graduated on the tube every 0.2 degrees (presumably Celsius). Overall length 8 ¾”; diameter ¾”.
label: Description
content: Maker: Unknown. The thermometer is a transfer from the U.S. Weather Bureau in 1959. Several of the instruments in the transfer are Russian from around 1940; some Cyrillic letters on this one suggest that it is Russian, or made for the Russian market. Marked: No 2894
label: Description
content: Reference: Anita McConnell, No Sea Too Deep. The History of Oceanographic Instruments, Adam Hilger, Ltd., 1982, pp. 98-100.
label: Location
content: Currently not on view
setName: label: See more items in
content: Medicine and Science: Physical Sciences
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: PH.316284
label: catalog number
content: 316284
label: accession number
content: 224564
objectType: label: Object Name
content: thermometer
physicalDescription: label: Measurements
content: overall: 8 3/4 in; 22.225 cm
label: Measurements
content: overall: 9 in x 3/4 in; 22.86 cm x 1.905 cm