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History of Science Museum

Drawing Instrument: Sliding Architectonic Plates to the Design of Thomas Carwitham, by Thomas Heath, London, 1720-1730(1723).

Inventory Number 18805.1.2


Brief Description
The only known example of Thomas Carwitham's 1723 design of an instrument for special-purpose architectural drafting. Two sectoral plates slide out from the main body to enable the fluting of classical columns and pilasters to be drawn in proportion.
Item type
Object
Provenance
Presented by Howard Dawes.
Primary inscriptions
"Tho: Heath Fecit.". On the sliding plates: "F. ye Flut.s of a Col.n in Plano", "For ye 7 Flut.s in a Pillas.r", "F. ye Flut.s in a Col.n Geom.l" and "F. m.t in a Module of a Col.n"
Object type
Drawing instrument
Dimensions
Height: 2mm Width: 118mm Depth: 67mm
Inventory No
18805.1.2

Description

Brass plate with two hinged sectors which swing out from the main body. The instrument follows the design of the painter and draughtsman Thomas Carwitham in his The Description and Use of an Architectonick Sector (1723). On the fixed part of the signed side are 60 inches divided into equal parts, from 1 to 60. The sectoral scales on this side are for minutes in a column module (0-60) and for flutes in a column (0-48). The fixed part of the reverse has a diagonal scale for the "Decimal part of a foot Inch & parts" and a scale for "An Inch & parts Divided in 12 E.P." (ie equal parts). The sectoral scales here are for the flutes of a column "in plano" (0-48) and for the 7 flutes in a pilaster" (0-29).