Surveyor's Transit

Surveyor's Transit

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This is marked "J. C. SALA MAKER SAN FRANCISCO 825." Sala termed it an Engineer's Complete Transit, and priced it at $235. The horizontal circle is silvered, graduated into 64 units (each equal to 100 mils), and read by opposite verniers to 30 parts. One mil (or military degree) equals 3.375 arc minutes. A variation arc, outside the compass at E, extends 30 degrees either way; the vernier reads to single minutes. The vertical arc, also silvered, is graduated into 30 minutes of arc, and read by vernier to single minutes. There is a clamp and tangent attachment to the telescope axis, as well as a gradienter attachment for determining gradients, distances, and differences of level.
Joseph Charles Sala (1841-1916) was born in Italy, moved to San Francisco around 1861, and worked for John Roach. Following Roach's death in 1891, Sala went into business for himself, advertising as "Successor to John Roach" and noting his many awards from the Mechanics' Institute of San Francisco.
Ref: J. C. Sala, Illustrated Catalogue and Manual of Civil Engineers' and Surveyors' Instruments (San Francisco, 1896).
Currently not on view
Object Name
surveyor's transit
date made
Sala, Joseph Charles
place made
United States: California, San Francisco
overall: 10 1/2 in; 26.67 cm
horizontal circle: 6 in; 15.24 cm
needle: 4 1/4 in; 10.795 cm
telescope: 10 1/2 in; 26.67 cm
hanging level: 5 in; 12.7 cm
overall: 13 7/8 in x 6 7/8 in x 10 1/2 in; 35.2425 cm x 17.4625 cm x 26.67 cm
ID Number
accession number
catalog number
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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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