Thermometer

This type of deep sea thermometer was designed by Henry Johnson in 1861. This example was made around 1870, and was used to record temperatures in the ocean depths. Although unsigned, it was retailed by Negretti & Zambra of London between 1864 and 1885, but did not prove popular.

Johnson's thermometer had as its element a bimetallic strip of riveted brass and steel. As these strips flexed under changing temperature zones in the water, they moved an index across the graduated dial (seen in the 'window'), and also pushed pins to record the extremes of temperature reached.

Johnson's thermometer proved to have only limited usefulness and was erratic in its measurements, as there was no correction for pressure. During the 1868-70 cruise of the 'Lightening', Charles Wyville Thomson (1830-1882) found the deep-sea thermometers unsatisfactory.

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Online ID:	000-180-000-980-C
Image Rights Holder:	National Museums Scotland
Project:	0504: National Museums Scotland Part 2 Project description \| View all records in project
Ref:	National Museums Scotland T.1935.17
Date:	Around 1870 c. 1870
Material:
Dimensions:
What:	Thermometer, deep sea, Johnson
Subject:	22. PHYSICS, Heat (Departmental Classification)
Who:	Johnson (Eponym)
Where:
Event:
Description:	One of a group of meteorological instruments and apparatus - a Johnson deep sea thermometer
References:	Glaisher, James. On a deep-sea thermometer invented by Henry Johnson Esq. Report of the British Association for the Advancement of Science, 1861 pp 58-9 McConnell, Anita. No sea too deep: The history of oceanographic instruments. Bristol: Hilger, 1982, pp 93-5 Middleton, Knowles. A History of the Thermometer and its uses in Meteorology. Baltimore, Maryland, 1966, pp 169-72
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