ProtractorsEngineering & Drafting
By the end of the 18th century, protractors were routinely manufactured by machinery, with the invention of dividing engines, such as Jesse Ramsden's, particularly important for enabling the precise division of a circle into fractions of angles. Makers produced protractors that read minute fractions of angles, particularly when a vernier was added to the instrument.
Mechanics or machinists also used protractors to draw designs for new types of machinery. For instance, there were several forms of limb protractors for draftsmen that both functioned as T-squares and provided angle measurement. Similarly, protractors assisted with the preparation of architectural drawings. The instruments were only displaced by the advent of computer-aided drafting in the late 20th century.
"Protractors - Engineering & Drafting" showing 1 items.
- This German silver protractor is in the shape of a quarter-circle. It is divided by half-degrees and marked by tens from 0° to 90°. Flat bars extend on both sides of the protractor. A movable arm extends from the vertex of the quadrant. A tab is cut out from this limb to permit reading the angle markings. The arm is secured by a brass thumbscrew that is near the origin point for the angle markings. The protractor is noticeably rusted and tarnished.
- There is a signature on the bottom edge: E. D. – Co. (/) NEW YORK & CHICAGO. Around 1880, Eugene Dietzgen emigrated from Germany and became a sales distributor for Keuffel & Esser in New York. In 1885, he began to sell mathematical instruments on his own in Chicago. In 1893, his firm started manufacturing instruments under the name Eugene Dietzgen Company. However, this protractor was not advertised in Dietzgen catalogs that were published between 1902 and 1947.
- Leslie Leland Locke (1875–1943) originally owned this protractor. A student at Grove City College, he earned a bachelor's degree in 1896 and a master's degree in 1900. He taught mathematics at Michigan State College, Adelphi College, and Brooklyn College and its Technical High School. He was interested in Peruvian quipu, mysterious and ancient systems of knotted strings used to store and communicate information and data. He donated his collection of early calculating machines to the Smithsonian and his early American textbooks to the University of Michigan.
- Reference: Louis C. Karpinski, "Leslie Leland Locke," Science n.s., 98, no. 2543 (24 September 1943): 274–275.
- Currently not on view
- date made
- ca 1900
- Eugene Dietzgen Company
- ID Number
- accession number
- catalog number
- Data Source
- National Museum of American History, Kenneth E. Behring Center