altazimuth theodolite
Datecirca 1840
Inventory Number5235
ClassificationTheodolite
Subject
Maker
Andrew Yeates
fl. 1840 - 1863
Place of OriginLondon, England
Dimensionstheodolite: 34.5 × 21.5 × 33.8 cm (13 9/16 × 8 7/16 × 13 5/16 in.)
case: 20.8 x 38.6 x 29.5 cm (8 3/16 x 15 3/16 x 11 5/8 in.)
case: 20.8 x 38.6 x 29.5 cm (8 3/16 x 15 3/16 x 11 5/8 in.)
Material
Accessoriescase, second eyepiece, plumb bob
DescriptionThis fine altazimuth theodolite has an inverted vertical semicircle mounted on conical trunions held between A-frame supports over a central magnetic compass. The front side of the semicircular arc has a silver scale divided 90°-0°-90° every 15', with a vernier reading to 1'. A reading microscope is attached to a teardrop-shaped bracket hanging from the top of one A support. The reverse of the semicircle is divided 30-0-30 every 1 directly onto the brass. It is a nonlinear scale marked "Diff. of Hypo & Base." The trunnion on this side has brass collar cast to have a descending arm. There is a milled locking screw on the collar. A slow-motion tangent screw attached to a leg of the A-frame operates against the arm.
The reversable telescope sits in hinged wye clamps fixed to on a narrow beam screwed to the top of the vertical semicircle. The telescope has adjustable cross-hairs, a focusing knob in the middle of the tube that extends the objective end, and a hanging bubble level with two windows. The eye-ring pins for the wye clamps are present, although at least one string is a replacement.
The magnetic compass is directly below the semicircular arc. It is silvered and bilevel, with a bar needle. The needle brake is operated by a brass lever outside the compass box. The wind rose has eight points with east and west reversed. The points are labeled in initials. The circumference is divided 0°-90°-0°-90°-0° every 10° on the lower level and 0°-360° every 1° on the upper level.
The compass sits on a circular brass plate with crossed bubble levels on two sides. The levels have fine adjustment screws. The base plate rotates over another carrying a silvered azimuth scale. The scale is divided 0°-360° every 15' with a vernier reading to 1'. There is a locking screw and a slow motion tangent screw. A bent arm has a threaded ring for insertion of a reading microscope (missing). This arm slides around the circumference of the scale in a track.
The entire assembly is mounted on a central brass column and freely rotates around it. There is a locking screw to stop rotation. It has a heart-shaped head. There is a slow-motion tangent screw as well with a milled head.
The central column has parallel plates with four leveling screws between them. The lowest plate has a large threaded socket to mate with the mounting on top of the tripod.
The mahogany case has two brass handles and is fitted to take the theodolite. Parts are padded with a dark felt. Accessories in the case include a second eyepiece for the telescope and a conical brass plumb bob. The case key is missing.
The reversable telescope sits in hinged wye clamps fixed to on a narrow beam screwed to the top of the vertical semicircle. The telescope has adjustable cross-hairs, a focusing knob in the middle of the tube that extends the objective end, and a hanging bubble level with two windows. The eye-ring pins for the wye clamps are present, although at least one string is a replacement.
The magnetic compass is directly below the semicircular arc. It is silvered and bilevel, with a bar needle. The needle brake is operated by a brass lever outside the compass box. The wind rose has eight points with east and west reversed. The points are labeled in initials. The circumference is divided 0°-90°-0°-90°-0° every 10° on the lower level and 0°-360° every 1° on the upper level.
The compass sits on a circular brass plate with crossed bubble levels on two sides. The levels have fine adjustment screws. The base plate rotates over another carrying a silvered azimuth scale. The scale is divided 0°-360° every 15' with a vernier reading to 1'. There is a locking screw and a slow motion tangent screw. A bent arm has a threaded ring for insertion of a reading microscope (missing). This arm slides around the circumference of the scale in a track.
The entire assembly is mounted on a central brass column and freely rotates around it. There is a locking screw to stop rotation. It has a heart-shaped head. There is a slow-motion tangent screw as well with a milled head.
The central column has parallel plates with four leveling screws between them. The lowest plate has a large threaded socket to mate with the mounting on top of the tripod.
The mahogany case has two brass handles and is fitted to take the theodolite. Parts are padded with a dark felt. Accessories in the case include a second eyepiece for the telescope and a conical brass plumb bob. The case key is missing.
Signedengraved on base above vernier: Andrew Yeates, / 12 Brighton Place New Kent Road / LONDON.
Curatorial RemarksTag in case reads: Davies Turner / Wheatland Mass. / G. Pontet Ltd.
ProvenanceDavid Wheatland purchased from Graham Pontet Ltd., London, May 13, 1967 (#3284). Donated to CHSI in March 1977.
Buff & Buff Manufacturing Company
Date: circa 1905
Accessories: wood case; leather case; right-angle prism; plumb bob; oil flask; tripod (5174b)
Object number: 5174a
W. & L. E. Gurley
Date: ca. 1884
Accessories: solar attachment; case; level; green filter; sun shade; tripod (5163b)
Object number: 5163a
Bausch, Lomb, Saegmuller Company
Date: 1905-1907
Accessories: screwdriver; key; dust cap; sunshade; carrying case; tripod (5162b)
Object number: 5162a
Legey
Date: circa 1838
Accessories: shades with double tabs (4); shades with single tab (4); screwdriver and square key.
Object number: 5268
John H. Temple
Date: 1850-1870
Accessories: carrying case; dust cap; leather straps; tripod (5166b)
Object number: 5166a
Alvan Clark and Sons
Date: 1910
Object number: 2003-1-0077b
See also/See also
