Maclean Square Navigational Protractor

Description:

This clear Perspex (acrylic glass) square protractor is divided by single degrees and marked by tens in the clockwise direction from 010° to 350°. A red arrow points to the origin. The marks for 090°, 180°, and 270° are replaced by the compass points E, S, and W, respectively. Diagonal lines to the four corners of the protractor are marked with the compass points NE, SE, SW, and NW. A pinhole is at the center of the protractor.

The interior of the protractor is marked with a grid. Tick marks (four per square) appear along the X and Y axes and around the outside edge of the grid. The top is labeled (in red): MACLEAN PROTRACTOR. Maker's marks are at the bottom: REGD. TRADE MK. AIRNAVA; J. D. MACLEAN ∙ Co. LONDON W.C.2. The protractor is stored in a tan cardboard case, which is printed with instructions for using the instrument. Marine and aviation navigators could employ it as a parallel rule, station pointer, and plotter. John Donald Maclean patented a rectangular protractor and parallel rule in the United States. No record of a trademark for "Airnava" was found in the United States or in Great Britain. This form of protractor is standard and is sometimes called a Douglas type of square protractor. Weems & Plath manufactures similar protractors in the 21st century.

Reference: Journal of Navigation 15, no. 4 (1962): front matter.

Date Made: 1950s-1960s

Maker: J. D. Maclean Co.

Location: Currently not on view

Place Made: United Kingdom: England, London

Subject: MathematicsProtractorNavigation

Subject:

See more items in: Medicine and Science: Mathematics, Science & Mathematics, Protractors

Exhibition:

Exhibition Location:

Credit Line: Gift of Howard Chapelle

Data Source: National Museum of American History

Id Number: 1987.0788.05Accession Number: 1987.0788Catalog Number: 1987.0788.05

Object Name: protractor

Physical Description: cardboard (overall material)plastic (overall material)Measurements: overall: .6 cm x 13.9 cm x 13.8 cm; 1/4 in x 5 15/32 in x 5 7/16 in

Guid: http://n2t.net/ark:/65665/ng49ca746a7-4fe2-704b-e053-15f76fa0b4fa

Record Id: nmah_904386

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