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.
- This brass semicircular protractor is divided by single degrees and marked by fives from 5° to 180°. The letter X is at the 90-degree mark. The upper right side of the protractor contains a shadow square. This is divided on both sides into sets of four units, each approximately 3/8" long and numbered from 1 to 12, for a total of 48 units on each side. The vertical side is marked: OMBRA VERSA. The horizontal side is marked (upside down): OMBRA RETTA.
- The scale on the "ombra versa" side measured tangents from 0 to 45°. The scale on the "ombra retta" (or "recta") side measured tangents from 45° to 90°. The lines for degrees and on the shadow square appear to be made by hand, perhaps by placing the instrument next to a pattern. The instrument is decorated with floral and solar motifs. The protractor rests in a brass base that unfolds to form a limb, which is chipped. There are two holes in the limb; the numbers 2 and 1 are scratched next to the holes. There are four holes in the base; the numbers 3 and 1 are scratched next to the outermost holes, which align with the holes on the limb. This instrument is Italian in origin and was likely made before 1800. New York University donated the object in 1963.
- Reference: J. A. Bennett, The Divided Circle (Oxford, 1987), 42–43.
- Currently not on view
- date made
- 18th century
- ID Number
- catalog number
- accession number
- Data Source
- National Museum of American History, Kenneth E. Behring Center