sextant
Datecirca 1794
Inventory Number0063
ClassificationSextant
Subject
Maker
Peter Dollond
1731 - 1820
Maker
John Dollond (II)
1733 - 1804
Cultural Region
Place of Origin
Dimensions34.8 x 38 x 11.4 cm (13 11/16 x 14 15/16 x 4 1/2 in.)
Material
Bibliography
DescriptionThe instrument's brass cross frame supports a reinforced index arm with vernier, clamp and tangent screw for precision readings. An adjustable index mirror is equipped with a hinged flap and three shades (red, green and blue). The frame also holds an horizon glass and mirror with three similar shades (red, green and blue), a 5" telescope in sight vane, and a fixed wooden handle. An engraved scale on the limb is graduated from -2° to 139° by single degrees and subdivided every 20'. Three removable feet were added to the sextant in order to lay it down horizontally on a table when not in use.
In Collection(s)
Signedon limb: Dollond London
Inscribedon handle: 10-2 (formerly 10-2-2)
on back scale: 63
Curatorial RemarksSince the two Dollond brothers worked together circa 1794, it is not clear whether Peter or John made this sextant. It was most likely a collaborative work.
FunctionThe sextant is an angle-measuring instrument used in navigation and astronomy to determine the altitude of celestial objects, such as the sun and stars. It can measure wider angles than the octant (up to 120°) and was commonly used to determine the angular separation between stars and the moon in order to find the longitude at sea by the lunar-distance method.
A video demonstration of a sextant was produced by the Harvard Museums of Science and Culture in association with the 2015 exhibit “Finding Our Way: Exploring Human Navigation” and is available on YouTube here.
A video demonstration of a sextant was produced by the Harvard Museums of Science and Culture in association with the 2015 exhibit “Finding Our Way: Exploring Human Navigation” and is available on YouTube here.
ProvenanceJefferson Physical Laboratory, Harvard University; transferred to CHSI May 1948.
Historical AttributesThis instrument was purchased (with Margate's Tables) at the then "book store" on 16 April 1794, for $120. It was used by Harvard's Hollis professor for teaching navigation and applied trigonometry.
Riggs & Brother
Date: 1820-1840
Accessories: keystone mahogany box, telescope, eyepiece shade
Object number: 5245
Benjamin Messer
Date: 1800-1820
Accessories: Keystone mahogany box, telescope
Object number: 5310
Peter A. Feathers
Date: 1842-1874
Accessories: Square mahogany box, one shade tube (8.4 cm), one erecting telescope (8.3 cm), and one inverting telescope (18.3 cm) with four crosshairs, one pin tool
Object number: 5333
Legey
Date: circa 1838
Accessories: shades with double tabs (4); shades with single tab (4); screwdriver and square key.
Object number: 5268
Ebenezer Hoppé
Date: circa 1809
Accessories: On 6/23/98, a telescope was found (1998-1-1412) that may belong to part of this sextant.
Object number: 5309
Edward Troughton
Date: 1804-1826
Accessories: Mahogany keystone box, stenciled in white paint on top and side of lid "P. Townsend"; 2 Telescopes; 1 Eyepiece
Object number: 5308
Spencer, Browning, & Company
Date: 1843-1850
Accessories: box with key, adjustment tool, telescope, eye tube, eyepiece shade
Object number: 5248
William Gerrard
Date: 1862-1890
Accessories: rectangular mahogany box, telescopes (2), sight tube, eyepiece shade, eyepiece
Object number: 5263
Heath & Company, Ltd.
Date: 1875-1890
Accessories: 7 1/8" telescope, 3 1/4" shade tube, 3 1/4" telescope, eyepiece shade, and mahogany box. with "4" on lid and "H" on front
Object number: 5311
David White Company
Date: 1945
Accessories: terrestrial kepler telescope, screwdriver, key, horizon mirror, adjusting wrench
Object number: 2003-1-0122