Casella Maximum Thermometer

This is a mercury-in-glass Phillips-type maximum thermometer. The bulb is spherical. The tube has a white enamel back; the scale on the front extends from zero to +125 degrees (presumably Fahrenheit) graduated every degree, and is marked "9714." The supporting white porcelain plate is marked "MAXIMUM" and "L. CASELLA. MAKER TO THE ADMIRALTY, London" and "No. 9714." The plate, in turn, is mounted on a wood back.
In this design, an air bubble separates a small bit of mercury from the main part of the column. When the temperature falls, the detached mercury remains in place indicating the maximum temperature attained until reset by the observer. John Phillips, an English geologist, introduced the form at the 1832 meeting of the British Association for the Advancement of Science. In 1856 he showed an improved form made by Louis P. Casella of London. Casella would later boast that, next to Phillips, he deserved "the exclusive merit of the introduction and arrangement of these most perfect maximum thermometers" thad had been widely adopted in Britain, on the Continent, and in the United States.
Ref: L. P. Casella, Illustrated and Descriptive Catalogue of Philosophical, Meteorological, Mathematical, Surveying, Optical and Photographic Instruments (London, 1860), p. 17.
Jack Morrell, John Phillips and the Business of Victorian Science (Aldershot, 2005).
Currently not on view
Object Name
maximum thermometer
date made
L. P. Casella
overall: 12 in; 30.48 cm
place made
United Kingdom: England, London
ID Number
catalog number
accession number
Measuring & Mapping
Smithsonian Institution
Thermometers and Hygrometers
See more items in
Medicine and Science: Physical Sciences
Thermometers and Hygrometers
Data Source
National Museum of American History, Kenneth E. Behring Center

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