altazimuth theodolite
Date: 1789-1825
Inventory Number: 5230a
Classification: Theodolite
Subject:
Maker: William Cary (c. 1759 - 1825)
Cultural Region:
Place of Origin:
Dimensions:
20.5 x 37 x 14 cm (8 1/16 x 14 9/16 x 5 1/2 in.)
instrument box: 21 x 29.7 x 16 cm (8 1/4 x 11 11/16 x 6 5/16 in.)
Accessories: small eyepiece (box)
DescriptionThe base of the instrument rotates horizontally on a graduated circle divided in 30' increments. Two verniers, in combination with a tangent screw, are added for precision reading. Moreover, a small microscopic lens can be positioned anywhere on the base to help read the fine engraved lines.
The compass is divided into the eight principal cardinal directions and it has a 0-360° graduated circle divided in one degree increments. No decoration is found on the compass card. A level, finally, is fixed on the base of the instrument. There is also a level on the telescope. The latter is mounted on a triangular support on which a graduated arc 90°-0-90° determines the angle of the instrument from the horizon. It has a vernier and a tangent screw for precision reading of altitude measurements.
Two small pins hold in place hook-like braces attached to the support, which can be removed to detach the telescopic tube and turn it back to front to make measurements. This instrument can thus be used as a Y-level.
The compass is divided into the eight principal cardinal directions and it has a 0-360° graduated circle divided in one degree increments. No decoration is found on the compass card. A level, finally, is fixed on the base of the instrument. There is also a level on the telescope. The latter is mounted on a triangular support on which a graduated arc 90°-0-90° determines the angle of the instrument from the horizon. It has a vernier and a tangent screw for precision reading of altitude measurements.
Two small pins hold in place hook-like braces attached to the support, which can be removed to detach the telescopic tube and turn it back to front to make measurements. This instrument can thus be used as a Y-level.
In Collection(s)
Signedon compass card: Cary London
FunctionThis is an instrument used in surveying to measure simultaneously the altitude and azimuth angle of a determined position.