Pocket Alt-Azimuth

Pocket Alt-Azimuth

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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 Fellow of the Royal Society of London, whose work ranged over a number of fields.
The U. S. Geological Survey transferred this example to the Smithsonian in 1907. The This inscription reads "L. Casella Maker to the Admiralty & Ordnance LONDON 166."
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
Object Name
Pocket Alt-Azimuth
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
See more items in
Medicine and Science: Physical Sciences
Measuring & Mapping
Surveying and Geodesy
Data Source
National Museum of American History
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