Troughton & Simms dumpy level
Datecirca 1840
Inventory Number5232
ClassificationSurveyor's Level
Subject
Maker
Troughton & Simms
1826 - 1923
User
Sir John Rennie
1794-1874
Cultural Region
Place of Origin
Dimensionslevel: 15.5 × 11 × 52 cm (6 1/8 × 4 5/16 × 20 1/2 in.)
case: 11.3 × 62.5 × 13.5 cm (4 7/16 × 24 5/8 × 5 5/16 in.)
case: 11.3 × 62.5 × 13.5 cm (4 7/16 × 24 5/8 × 5 5/16 in.)
Material
Accessoriesmahogany box with brass hinges and hooks
DescriptionBrass dumpy level consisting of the following major components (from top to bottom): compass; spirit level; telescope tube; foot plate with four leveling screws.
Mounted on columns extending from the level bar is a brass compass. The compass has a silvered face with an eight point "star" rose. Each cardinal and intercardinal point is labeled, with E and W in reversed positions. The arms extending to the cardinal points are engraved with a floral pattern. Two scales are engraved around the circumference of the compass. The outermost scale is raised and has values ranging from 0 to 360 (counterclockwise), graduated into ones. The innermost scale has values ascending from 0 to 90 (N to E), descending from 90 to 0 (E to S), ascending from 0 to 90 (S to W), and descending from 90 to 0 (W to N). This scale is graduated into tens.
Fixed to the top of the telescope tube is a spirit level with a single oval glass window. The window is etched with a single line to either side of the compass, halfway between the latter and the edge of the window.
The telescope tube has knurling at the eyepiece end of the larger tube. Bolted to the side of the tube between the eyepiece and the compass is a single knob with two knurled rings around its edge. The telescope tube sits on two brass blocks fixed to the level bar. Below the level bar at either end is a rectangular brass tube, inside of which brass pins are visible.
Four leveling screws, each with a circular knob having two knurled rings around its edge, rest on the circular foot plate, first passing through and identical brass disc. Above the screws is an additional, smaller disc with knurling.
The instrument is stored in two pieces in a mahogany case with brass hinges and hooks.
Mounted on columns extending from the level bar is a brass compass. The compass has a silvered face with an eight point "star" rose. Each cardinal and intercardinal point is labeled, with E and W in reversed positions. The arms extending to the cardinal points are engraved with a floral pattern. Two scales are engraved around the circumference of the compass. The outermost scale is raised and has values ranging from 0 to 360 (counterclockwise), graduated into ones. The innermost scale has values ascending from 0 to 90 (N to E), descending from 90 to 0 (E to S), ascending from 0 to 90 (S to W), and descending from 90 to 0 (W to N). This scale is graduated into tens.
Fixed to the top of the telescope tube is a spirit level with a single oval glass window. The window is etched with a single line to either side of the compass, halfway between the latter and the edge of the window.
The telescope tube has knurling at the eyepiece end of the larger tube. Bolted to the side of the tube between the eyepiece and the compass is a single knob with two knurled rings around its edge. The telescope tube sits on two brass blocks fixed to the level bar. Below the level bar at either end is a rectangular brass tube, inside of which brass pins are visible.
Four leveling screws, each with a circular knob having two knurled rings around its edge, rest on the circular foot plate, first passing through and identical brass disc. Above the screws is an additional, smaller disc with knurling.
The instrument is stored in two pieces in a mahogany case with brass hinges and hooks.
Signedengraved on compass face: Troughton & Simms / LONDON. ;
engraved on edge of level bar: Sir. J. Rennie.
Curatorial RemarksThis object was previously numbered DW0355.
FunctionFor use in surveying, to measure contours.
After mounting the dumpy level on a tripod at his starting location, the user levels the instrument by means of the spirit level and the leveling screws. Then he sights a stadia rod through the telescope, moving the rod as needed until the target is centered behind the telescope's cross hairs. The difference in height between the telescope and the rod target indicates the gain in elevation over the horizontal distance between the two.
The compass attached on the level bar may be used to indicate direction of measurement, or to calculate horizontal angles.
After mounting the dumpy level on a tripod at his starting location, the user levels the instrument by means of the spirit level and the leveling screws. Then he sights a stadia rod through the telescope, moving the rod as needed until the target is centered behind the telescope's cross hairs. The difference in height between the telescope and the rod target indicates the gain in elevation over the horizontal distance between the two.
The compass attached on the level bar may be used to indicate direction of measurement, or to calculate horizontal angles.
ProvenanceDavid Wheatland purchased from Alain Brieux, Paris, March 8, 1968 (lot 30/18). Donated to CHSI February 1977.
Historical AttributesSir John Rennie, the owner of this instrument, oversaw construction of the London Bridge.
Peter & John Dollond
Date: 1780-1800
Accessories: mahogany box with brass hooks, hinges, and handle; tripod (see 5240b)
Object number: 5240a
Troughton & Simms
Date: circa 1840
Accessories: mahogany box with brass handle; sun shade for telescope
Object number: 5234
Spencer, Browning & Rust
Date: circa 1800
Accessories: mahogany case with brass hooks and hinges; lens cap
Object number: 5137
Edward Nairne
Date: circa 1790
Accessories: mahogany box with clasp closure
Object number: 5228
Buff & Berger
Date: circa 1880
Accessories: mahogany case; sunshade; screws; dust cover
Object number: 5143a
John Frederick Newman
Date: circa 1835
Accessories: mahogany case with brass hinges and hooks
Object number: 5239
Buff & Berger
Date: circa 1880
Accessories: mahogany case; sunshade; screws; dust cover; tripod (5144b)
Object number: 5144a
James E. Moody
Date: circa 1880
Accessories: mahogany case; sunshade; dust cap; tripod (5141b)
Object number: 5141a
Iszard-Warren Co., Inc.
Date: circa 1910
Accessories: mahogany case with brass corners and lock; key missing; leather strap; screwdriver; dust cover; sunshade; tripod, see 5150b
Object number: 5150a
John H. Temple
Date: circa 1870
Accessories: mahogany case; sunshade; tripod (5142b)
Object number: 5142a
R. Iseli
Date: circa 1880
Accessories: walnut case with two adjustment tools, objective lens cap, and lens shade; Iseli trade card (inside box lid)
Object number: 5229
See also/See also
