graphometer with telescopic sights
Date1753
Inventory NumberDW0272a
ClassificationGraphometer
Subject
Maker
Joseph Simon Guibout
1715 - 1780
Cultural Region
Place of Origin
Dimensions15 × 26.5 × 29.5 cm (5 7/8 × 10 7/16 × 11 5/8 in.)
Material
DescriptionThis is a brass graphometer whose original slit sights have been removed and replaced with telescopic sights.
The graphometer is divided 90°-0°-90° every 30' with verniers on the end of the sighting alidade reading to 1'. The sighting alidade (DW0272b) is currently unattached to the graphometer. It carries a telescope mounted on a sector hinge so that it is adjustable in inclination.
The graphometer's semicircle is embedded in a heavy wooden frame. There are ivory pegs set into the frame at 20° intervals. One is missing. There are two sets of holes for the pegs--one inside the divided arc and one outside. The baseline reference telescope is mounted underneath the straight edge of the wood frame and has a fine motion screw for adjusting its position. Also mounted underneath the frame are crossed bubble levels.
The wooden frame is attached to a brass column that rotates on top of a tribrach base. A knurled tangent screw is provided for fine fixing of the direction in which the graphometer is pointed. There is also a clamping screw and locking screw. The base has leveling screw feet.
Despite the crude appearance of the wood frame, the instrument is very well thought out and the brass work well done.
The graphometer is divided 90°-0°-90° every 30' with verniers on the end of the sighting alidade reading to 1'. The sighting alidade (DW0272b) is currently unattached to the graphometer. It carries a telescope mounted on a sector hinge so that it is adjustable in inclination.
The graphometer's semicircle is embedded in a heavy wooden frame. There are ivory pegs set into the frame at 20° intervals. One is missing. There are two sets of holes for the pegs--one inside the divided arc and one outside. The baseline reference telescope is mounted underneath the straight edge of the wood frame and has a fine motion screw for adjusting its position. Also mounted underneath the frame are crossed bubble levels.
The wooden frame is attached to a brass column that rotates on top of a tribrach base. A knurled tangent screw is provided for fine fixing of the direction in which the graphometer is pointed. There is also a clamping screw and locking screw. The base has leveling screw feet.
Despite the crude appearance of the wood frame, the instrument is very well thought out and the brass work well done.
Signedengraved on baseline: Guibout AParis 1753
Inscribedon divided scale: De Clinaison Sud est et Nord Ouest
on divided scale: DeClinaison Sud Ouest et Nord est
Curatorial RemarksSimilar to a graphometer with telescopic sights by Lenoir, Paris, late 18th century, at the Whipple Museum (depicted in Bennett, <i>Divided Circle</i>, 85.)
ProvenanceDavid Wheatland purchased from Roux-Devillas Paris, July 7, 1967 (lot 7/B).
Michael Butterfield
Date: 1675-1715
Accessories: leather case stamped with fleur-de-lys
Object number: DW0663
Benjamin Martin
Date: 1738-1777
Accessories: brass cover; ball-and-socket mount (DW0511c); tripod (DW0511b).
Object number: DW0511a
W. & L. E. Gurley
Date: ca. 1884
Accessories: solar attachment; case; level; green filter; sun shade; tripod (5163b)
Object number: 5163a
See also/See also
