|
| Catalogue |
|
 Theodolite The horizontal circle comprises a ring of gilt brass, which accommodates a central silvered brass circular glazed compass box, around which rotates a silvered brass ring with three mounting plates for the supports to the vertical semicircle. The compass plate has lines for the four cardinal directions, marked 'SEPT[Ebar]TRIO', 'ORIENS' (to the right of north), 'MERIDIES', 'OCCIDENS', and a target line offset for variation; steel needle with brass cap to mount. Each mounting plate has two holes, one for a locating pin, the other for a securing screw. The circle has an outer degree scale 0 to 90 four times, divided to 10, subdivided to 5 and to 1, numbered by 10. Inside this is a scale of hours numbered 0 to 24 and 0 to 12 trice, divided to 1 hour, subdivided to 1/2 and to 1/4 with alternate hatching, numbered by 1 hour. A vertical semicircle is carried by an 'A' frame rising to the pivot for the semicircle, with a decorated scrollwork joining piece incorporating the pointed target for a plumbline (missing), and a strut hinged to the semicircle giving lateral support. The lower part of the 'A' frame has two studs with holes for a line. One side of the semicircle has decoration with mirror gilding, which is also used on other parts of the instrument, the other has an outer degree scale 0 to 90 to 0, divided to 10, subdivided to 5 and to 1, numbered by 10, and an inner scale 0 to 12, divided to 1, subdivided to 1/2 and to 1/4 with alternate hatching, numbered by 1. Pinhole sights are attached by screws to either end of the diametric arm. Jim Bennett |