Parallel rules help draftsmen, surveyors, cartographers, architects, and navigators draw accurate parallel lines. The instrument comes in two main forms: two rectangular straight edges connected by brass or silver hinges, or a single frame surrounding a roller. The first type was known in Europe by 1600, while Englishman A. George Eckhardt is credited with inventing the second in 1771. The parallel rule was superseded for most uses by the T-square in the 19th century, but navigators continue to use parallel rules in conjunction with gridded charts.
The mathematics collections contain about twenty parallel rules and combination instruments, dating from the late 18th century to the late 20th century and ranging in length from 6 to 24 inches. The objects are made from ebony and other woods, brass, German silver, and plastic. They were manufactured in the United States, England, Italy, and Taiwan. They were used for military surveying, in navigation, in business, in art and technical drawing, and for placing handles on caskets. Several of the objects in this group illustrate innovations added to the basic instrument.
The digitization of this group of artifacts was made possible through the generous support of Edward and Diane Straker.
"Parallel Rules - Overview" showing 1 items.
- This 24" boxwood instrument has two blades held together by three metal (possibly copper) hinges. The middle hinge is curved and has a slide with a thumbscrew that allows the user to fix the separation between the blades at a desired width. This hinge is marked: PAT APL'D FOR. The top blade is 1/2" wide and 22" long. The bottom blade is 7/8" wide, divided to 1/2", and numbered by ones from 1 to 12 to 1. The back is marked: D. W. BELLOWS (/) MFR. (/) PAWTUCKET, R.I.
- Dexter W. Bellows (1856–1940) was a funeral director in Pawtucket, R.I., from 1892 until his death. He designed this rule in 1896 to assist in placing handles evenly along the sides of caskets. No patent record has been found, but the National Casket Company of Baltimore is known to have distributed the rule.
- References: Peggy A. Kidwell, "American Parallel Rules: Invention on the Fringes of Industry," Rittenhouse 10, no. 39 (1996): 90–96; "The Bellows Gauge for Placing Casket Handles," Providence Journal of Commerce (1896): 32; Bellows Funeral Chapel, "Our History," http://www.bellowsfuneralchapel.com/?page=ourhistory0.
- Currently not on view
- date made
- Bellows, Dexter W.
- ID Number
- catalog number
- accession number
- Data Source
- National Museum of American History, Kenneth E. Behring Center