Thermometer, designed by W.A. Miller, made by L.P. Casella

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This type of pressure-resistant, deep sea thermometer (pictured here with its copper case) was designed by Dr W. A. Miller (1817-70), Vice-President of the Royal Society. It was constructed from 1869 by the firm of L.P. Casella, scientific instrument makers based in London, and was known as the Miller-Casella thermometer.

The full bulb of the thermometer was surrounded by an outer glass sheath, the space between the two being filled with a mixture of alcohol, its vapour and some air. This mixture yielded to the pressure of the water, thus relieving the thermometer bulb itself, which would otherwise have broken. Maximum and minimum temperatures could be recorded. The thermometer fits into a brass container for protection.

During the 1868-70 cruise of the 'Lightning' Wyville Thomson (1830-882) had found existing deep-sea thermometers unsatisfactory, and had returned to the original U-tube registering thermometer devised by James Six in 1780. A registering segment of mercury was contained in the U, carrying floating steel indexes which were left behind at the highest point reached by the mercury.

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• Online ID: 000-180-000-974-C
• Image Rights Holder: National Museums Scotland
• Project: National Museums Scotland Part 2
  Project description   View all records in project
• Ref: National Museums Scotland  T.1911.59
• Date: Around 1870
  
• Material: Copper case. Inscription: HO [upward pointing arrow] 122 [Admiralty mark]
  Specimen / nautical instrument / meteorological instrument / the
  
• Dimensions:
• What: Specimen / nautical instrument / meteorological instrument / the
  
• Subject: 22. PHYSICS, Heat (Departmental Classification)
  
• Who: Admiralty (Owner)
  Buchanan (Eponym)
  L. Casella, London (Maker)
  Miller (Eponym)
  
• Where: England, London
  
• Event:
• Description: One of a collection of surveying, nautical, astronomical, meteorological and drawing instruments - Buchanan's Casella-Miller maximum and minimum deep sea pattern thermometer, marked, in a copper case
  
• References:
  • Carpenter, Jefferys & Thomson. Report on the 'Porcupine' Expedition. Proceedings of the Royal Society of London, Vol 18 (1870), pp 408-411. 
  • McConnell, Anita. No sea too deep: The history of oceanographic instruments. Bristol: Hilger, 1982, pp 97-98. 
  • Miller, W.A. Note upon a Self-registering Thermometer adapted to Deep-sea soundings. Proceedings of the Royal Society of London, Vol 17 (1869), pp 482-6 
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