Protractors - Surveying
Since the first protractors appeared near the turn of the 17th century, around the same time that the technique of triangulation was developed for surveying, their utility for this activity appeared evident from early on. Surveyors typically carried at least one protractor in their field kits. The instrument might be combined with another drawing instrument, such as a set of parallel rules. By the 19th century, makers tried to blend convenience with multi-functionality, offering rectangular protractors that fit easily in a case or pocket and that were packed with aids for reducing real-world distances to proportional scales. They also showed off their improving craftsmanship with fine objects that retained accuracy in measurement. (See also the page on Engineering & Drafting.)
"Protractors - Surveying" showing 1 items.
- Protractors, devices for measuring and drawing angles, were used in professional practice as well as by schoolchildren. The instruments manufactured for surveyors, draftsmen, and the like could be of quite high quality. This circular protractor is one of at least three in the Smithsonian collections that were produced by Kern & Co. of Aarau, Switzerland. Made of German silver, an alloy of 60% copper, 20% nickel, and 20% zinc, it is graduated along the outer edge to one-quarter degree and marked by tens from 0 to 350 in both the clockwise and counter-clockwise directions.
- A center cross-plate, which instrument dealers called a "horncentre," contains crosshairs to assist with placing the protractor on a drawing. A movable arm attached to the center contains a vernier scale that allows the user to read angles to one minute of arc. The arm also has a blade-like extension of 3 inches. There are indentions on the interior of the protractor at 0, 90/270, 180, and 270/90 degrees.
- Across its diameter, the protractor is engraved: U.S.G.S. No. 8. Stamped on the back of the vernier arm is the number 88. The protractor was purchased by the U.S. Geological Survey between 1879 and 1907, when it was transferred to the Smithsonian. According to the accession record, it was already "badly tarnished" in 1907. Protractors of this style were manufactured by Kern at least as early as 1867. In 1878 and 1881, respectively, the Troy, N.Y., factory of W. & L. E. Gurley, and New York dealer William Y. McAllister sold Kern circular protractors of this size (10" diameter) for $20.00.
- See also ID numbers 1977.0460.02 and 1978.2291.01.
- References: William Y. McAllister, A Priced and Illustrated Catalogue of Mathematical Instruments . . . Particular Attention is Called to the Swiss Drawing Instruments (Philadelphia, 1867), 23; W. & L. E. Gurley, A Manual of the Principal Instruments Used in American Engineering and Surveying (Troy, N.Y., 1878), 166; William Y. McAllister, A Priced and Illustrated Catalogue of Mathematical Instruments (Philadelphia, 1881), 35.
- Currently not on view
- date made
- Kern & Co.
- ID Number
- accession number
- catalog number
- Data Source
- National Museum of American History, Kenneth E. Behring Center