6 in transit railway theodolite with longitudinal level over the telescope and constructed without an altitude circle. Reading to 10 seconds of arc. Trough compass and other accessories. Bronzed brass. 3-screw levelling head and tribrach.
Used for railway surveying; eg setting out masonry skew-arch bridges.
For the tripod see https://ice-museum-scotland.hw.ac.uk/product/1977-017-1/.
This theodolite was donated to the museum in 1977 by Carfrae & Morrison CE, Edinburgh. For a description of the setting out of a skew arch bridge see Figs 12 & 13 of Thomas Carfrae’s copy of W Davis Haskoll CE’s “Railway Construction for the Use of the Engineer Contractor &c” Atchley & Co London 1857.
A book of instructions for the use of theodolites is in the collection (see https://ice-museum-scotland.hw.ac.uk/product/1998-001/).