Dollond Rolling Parallel Rule in Case

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.

Date Made: late 18th century

Maker: Dollond

Location: Currently not on view

Place Made: United Kingdom: England, London

Subject: MathematicsDrafting, Engineering

Subject:

See more items in: Medicine and Science: Mathematics, Science & Mathematics, Parallel Rules

Exhibition:

Exhibition Location:

Data Source: National Museum of American History

Id Number: MA.323499Catalog Number: 323499Accession Number: 250508

Object Name: parallel rule in caseparallel rule

Physical Description: wood (overall material)fabric (overall material)leather (overall material)ebony (overall material)brass (overall material)ivory (overall material)glass (overall material)Measurements: overall: 1.8 cm x 17.8 cm x 5 cm; 23/32 in x 7 in x 1 31/32 in

Guid: http://n2t.net/ark:/65665/ng49ca746a5-0622-704b-e053-15f76fa0b4fa

Record Id: nmah_690220

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