Dollond Rolling Parallel Rule in Case
date: label: date made
content: late 18th century
name: label: maker
content: Dollond
notes: label: Description
content: 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.
label: Description
content: 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.
label: Description
content: References: Deborah J. Warner, “Browse by Maker: Dollond,” <i>National Museum of American History Physical Sciences Collection: Surveying and Geodesy </i>, http://amhistory.si.edu/surveying/maker.cfm?makerid=10; Maya Hambly, <i>Drawing Instruments: 1580–1980 </i> (London: Sotheby's Publications, 1988), 111–113; <i>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</i> (London, [1780–1805]); accession file.
label: Location
content: Currently not on view
place: label: place made
content: United Kingdom: England, London
topic: label: Subject
content: Mathematics
label: Subject
content: Drafting, Engineering
setName: label: See more items in
content: Medicine and Science: Mathematics
label: See more items in
content: Science & Mathematics
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content: Parallel Rules
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: MA.323499
label: catalog number
content: 323499
label: accession number
content: 250508
objectType: label: Object Name
content: parallel rule in case
label: Object Name
content: parallel rule
physicalDescription: label: Physical Description
content: wood (overall material)
label: Physical Description
content: fabric (overall material)
label: Physical Description
content: leather (overall material)
label: Physical Description
content: ebony (overall material)
label: Physical Description
content: brass (overall material)
label: Physical Description
content: ivory (overall material)
label: Physical Description
content: glass (overall material)
label: Measurements
content: overall: 1.8 cm x 17.8 cm x 5 cm; 23/32 in x 7 in x 1 31/32 in