Parallel Rules

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 The parallel rule was superseded for most uses by the T-square in the 19th century, but navigators continue to use parallel rules in conjunction with gridded charts.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.

Acknowledgement

The digitization of this group of artifacts was made possible through the generous support of Edward and Diane Straker.

This ebony ruler has ivory edges divided to 1/12" and numbered by ones from 1 to 6. Ivory rollers at each end of the ruler's interior are numbered by sixes from 6 to 18 and within brass housings.
Description
This ebony ruler has ivory edges divided to 1/12" and numbered by ones from 1 to 6. Ivory rollers at each end of the ruler's interior are numbered by sixes from 6 to 18 and within brass housings. The rollers are connected by a metal rod that runs through a brass and paper counting dial numbered by ones from 1 to 12. A metal pointer or index attached to this dial shows the number of inches the rule has rolled. The rod is covered with ebony. The right end of the rule is marked: DOLLOND (/) LONDON. A wooden case is covered with black leather and lined with green velvet.
The Dollond family began to make eyeglasses, telescopes, and scientific instruments in London in the mid-18th century. A. George Eckhardt invented a rolling parallel ruler in 1771 and gave the patent to the firm. In the late 18th century, brothers and partners Peter and John Dollond advertised four forms of parallel rulers: an ebony rule with unnumbered brass rollers; a rule adding ivory scales on the rollers; a rule adding ivory scales along the edges; and a rule adding the measuring dial with index. This object is a 6" example of the fourth type of rule and sold for 1 pound, 6 shillings. The firm merged with Aitchison & Co. in 1927 and was purchased by Boots Opticians in 2009.
References: Deborah J. Warner, “Browse by Maker: Dollond,” National Museum of American History Physical Sciences Collection: Surveying and Geodesy , http://amhistory.si.edu/surveying/maker.cfm?makerid=10; Maya Hambly, Drawing Instruments: 1580–1980 (London: Sotheby's Publications, 1988), 111–113; A Catalogue of Retail Prices of Optical, Mathematical and Philsophical Instruments made by P. and J. Dollond, Opticians to His Majesty in St. Paul's Church-Yard and St. James Haymarket (London, [1780–1805]); accession file.
Location
Currently not on view
date made
late 18th century
maker
Dollond
ID Number
MA.323499
catalog number
323499
accession number
250508
This 6" ebony instrument has three blades, apparently cut from a single rectangle of wood, and is held together by intricate brass hinges.
Description
This 6" ebony instrument has three blades, apparently cut from a single rectangle of wood, and is held together by intricate brass hinges. Surveyors, cartographers, navigators, and draftsmen began using parallel rules in the 18th century to easily draw parallel lines separated by various widths. These instruments were also used for reducing or enlarging scaled drawings.
According to the donor, the rule was brought to this continent by Alexander Matheson (1788–1866), an English officer who brought troops from the West Indies to fight against the Americans in the War of 1812. After the war, he helped build the Rideau Canal and settled near Perth, Ontario. His grandson, Alexander Matheson Richey (1826–1913), a lumberman who moved to Chicago, also used the instrument.
References: Maya Hambly, Drawing Instruments: 1580–1980 (London: Sotheby's Publications, 1988), 111; Ken W. Watson, "Smiths Falls Locks 28–31," Rideau Canal World Heritage Site, http://www.rideau-info.com/canal/history/locks/h28-31-smithsfalls.html; "The Town of Perth: The Settlement of Retired Military Heroes on 'the Scotch Line,'" Toronto Daily Mail (May 14, 1887), 6–7, 10; accession file.
Location
Currently not on view
date made
early 19th century
ID Number
MA.321753
catalog number
321753
accession number
243754
This 21" German silver hinged parallel rule has two small knobs for positioning the instrument. Brass round pieces cover the screws securing the two hinges. An indentation is on both blades at the center of the rule, with a line marking the center.
Description
This 21" German silver hinged parallel rule has two small knobs for positioning the instrument. Brass round pieces cover the screws securing the two hinges. An indentation is on both blades at the center of the rule, with a line marking the center. The edges of the top blade are marked as a rectangular protractor, and the edges of the bottom blade are marked for nautical compass points.
The center of the top blade is marked: U. S. C. & G. S. NO. 331. The right end of the top blade is marked: CAPT. FIELD'S IMPD. The right end of the lower blade is marked: H. HUGHES & SON LTD. LONDON. The left end has the firm's "HUSUN" logo, with a sun above the letters and waves below the letters.
Capt. William Andrew Field (about 1796–1871) of Britain added a protractor and compass scales to hinged parallel rules in 1854. This made it easier for ship navigators to move the rule without losing track of the ship's course. Henry Hughes & Son made marine and aeronautical navigational instruments in London from 1828 to 1947 and incorporated in 1903. According to the accession file, the U.S. Coast & Geodetic Survey acquired this rule on August 21, 1919, and last issued it on September 5, 1922. Compare to MA.309662 and MA.309663.
References: "Field's Parallel Rule," The Nautical Magazine and Naval Chronicle 23, no. 5 (May 1854): 280; Peggy A. Kidwell, "American Parallel Rules: Invention on the Fringes of Industry," Rittenhouse 10, no. 39 (1996): 90–96; National Maritime Museum, "Captain Field's Improved Parallel Rule," Object ID NAV0602, http://collections.rmg.co.uk/collections/objects/42814.html; Science Museum Group, "Henry Hughes and Son Limited," Collections Online – People, http://collectionsonline.nmsi.ac.uk/detail.php?type=related&kv=58792&t=people.
Location
Currently not on view
date made
1919
ID Number
MA.309661
catalog number
309661
accession number
106954
This 21" German silver hinged parallel rule has two knobs for positioning the instrument. Brass round pieces cover the screws securing the two hinges.
Description
This 21" German silver hinged parallel rule has two knobs for positioning the instrument. Brass round pieces cover the screws securing the two hinges. The edges of the top blade are marked as a rectangular protractor, and the edges of the bottom blade are marked for nautical compass points.
The right end of the upper blade is marked: CAPT. FIELD'S IMPD. The center of the lower blade is marked: U. S. C. & G. S. NO. H. 398. The left end has the firm's "HUSUN" logo for the London instrument maker H. Hughes & Son, with a sun above the letters and waves below the letters. A circle around the logo is marked: REGISTERED TRADE MARK (/) GT BRITAIN.
Capt. William Andrew Field (about 1796–1871) of Britain added a protractor and compass scales to hinged parallel rules in 1854. This made it easier for ship navigators to move the rule without losing track of the ship's course. Henry Hughes & Son made marine and aeronautical navigational instruments in London from 1828 to 1947 and incorporated in 1903. According to the accession file, the U.S. Coast & Geodetic Survey acquired this rule on November 6, 1923, and last issued it on February 16, 1924. Compare to MA.309661 and MA.309663.
References: "Field's Parallel Rule," The Nautical Magazine and Naval Chronicle 23, no. 5 (May 1854): 280; Peggy A. Kidwell, "American Parallel Rules: Invention on the Fringes of Industry," Rittenhouse 10, no. 39 (1996): 90–96; National Maritime Museum, "Captain Field's Improved Parallel Rule," Object ID NAV0602, http://collections.rmg.co.uk/collections/objects/42814.html; Science Museum Group, "Henry Hughes and Son Limited," Collections Online – People, http://collectionsonline.nmsi.ac.uk/detail.php?type=related&kv=58792&t=people.
Location
Currently not on view
date made
1923
maker
H. Hughes & Son, Ltd.
ID Number
MA.309662
catalog number
309662
accession number
106954

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