Casella Pocket Altazimuth

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The Pocket Altazimuth combines a sighting telescope with a magnetic compass for determining bearings, and a pendulum (or wheel) clinometer for determining vertical inclinations. Small, compact, and accurate, it was said to be especially useful for travelers and military surveys.
L. Casella introduced the form in 1864, noting that is was "improved and modified by the kind assistance of Francis Galton, F.R.S." The reference is to Francis Galton, (1822-1911), a gentleman scientist who was a Fellow of the Royal Society of London, and whose work ranged over a number of fields.
This example is signed "L. Casella Maker to the Admiralty & Ordnance LONDON 166." The U. S. Geological Survey transferred it to the Smithsonian in 1907.
Ref: L. P. Casella, An Illustrated and Descriptive Catalogue of Surveying, Philosophical, Mathematical, Optical, Photographic, and Standard Meteorological Instruments (London, [about 1871]), p. 71.
Karl Pearson, (Cambridge, 1914-1930), vol. 2, p. 50.
Currently not on view
Casella, Louis Paschal
overall: 3 in x 5 1/2 in x 1 1/4 in; 7.62 cm x 13.97 cm x 3.175 cm
overall: 2 7/8 in x 1 1/4 in x 5 1/2 in; 7.3025 cm x 3.175 cm x 13.97 cm
ID Number
catalog number
accession number
Credit Line
U.S. Geological Survey
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Medicine and Science: Physical Sciences
Measuring & Mapping
Surveying and Geodesy
Data Source
National Museum of American History


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