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Physical Sciences Collection - Surveying and Geodesy

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Transit - click to enlarge

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Transit

Catalogue number:
PH*334889

Inscriptions:
"Heller & Brightly Makers 5512 Philadelphia"

Dimensions:
height 11.5 inches (without leveling base); horizontal circle 7.5 inches diameter; vertical arc 2.5 inches radius; magnetic compass 5.25 inches diameter (needle is missing); telescope 11.5 inches long; hanging level 6.25 inches

Discussion:

Heller & Brightly advertised this as an Improved Complete 'Combined Transit and Leveling Instrument' For Civil Engineers and Surveyors. This example, which belonged to the University of Pittsburgh, was made around 1882. New, it cost $220. The horizontal circle is silvered, graduated every 30 minutes of arc, and read by two verniers to single minutes; one vernier is covered by a level vial. The vertical arc, also silvered, is read by a single vernier to 30 seconds. To keep dust out of the working parts, the joints are sealed. To reduce weight, the vertical standards are ribbed and braced. To reduce backlash, the tangent screw is provided with a fixed spiral spring and follower. This transit instrument is equipped so that a surveyor can determine horizontal distances by observing a distant graduated rod. To that end, it has an exceptionally powerful telescope, and its eyepiece has two horizontal wires so arranged that they encompass a tenth of a foot on a rod placed at a distance of 100 feet. Stadia surveying, as this practice is known, originated in Europe in the late 18th century and was introduced to the United States in the 1840s. The box in which the transit is packed is equipped with springs, to accommodate the instrument in any direction. In addition, there is a solar attachment designed by George N. Saegmuller, and marked "HELLER & BRIGHTLY MAKERS PHILA." and "PAT. May 3. 81."

Ref: Heller & Brightly, Remarks on Surveying Instruments (Philadelphia, 1886).

Further Information:

Transit
Heller & Brightly
Saegmuller

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