Full Details

Name and Model Number Ebsworth (bone or ivory)
4.5-inch English Sector
Country of Origin England
Date of Manufacture c.1820-26
Front Scales Sector: L S C and inch
Back Scales Sector: S T T and T S N
Scale Length 4.5-in (9-in unfolded)
Type of Rule Rule
Construction Bone or ivory with a brass hinge
Area of Use Topography
Comment Calculating instrument attributed to Galileo & others. This example has logarithmic scales in addition to the sector scales. The scales on the English sector differ significantly from those on Gunnery sectors. Used partially folded with a pair of dividers. The English sector was commonly included in drafting instrument sets in the 19th Century. Made by Richard Ebsworth, 41 Fleet St., London, c.1820-1826. This example is very rare because of its unusual length, 4.5 inches rather than the more common 6 inches, and because it could have been made by Ebsworth at its Fleet Street location for only 6 or 7 years. Searches of the Internet and eBay have not revealed any other examples of a sector made by Ebsworth.
Rarity RRRR
Donor Collection of Ed Chamberlain
Match Number 176
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In conjunction with our 'donors' we assign a rarity rating to each item, based on the system devised by Herman van Herwijnen
(1929 - 2004), renowned Dutch collector, author, and creator of Herman's Archive, a collection of 5,000 slide rule images on CD.
• RR = Rare - 1 of 25 collectors has one; it may take a year to find an example in the marketplace.
• RRR = Very Rare - only a few known to collectors; may be several years before it comes up for sale.
• RRRR = Extremely Rare - a museum piece; unlikely that an example will come up for sale.