This instrument was made between 1878, when the United States Coast Survey became the United States Coast and Geodetic Survey, and the death of L. P. Casella in 1897. Casella termed it a "Travellers' Transit Theodolite . . . with telescope in centre, much used by the Indian Government, as well as by the United States Coast Survey." With carrying case, it weighed 5.25 pounds and cost £19.10.0. The horizontal and vertical circles are silvered, and read by verniers and magnifiers to single minutes.
Refs: L. P. Casella, List of a Few Instruments in General Use, Selected
from the General Catalogue of Standard Meteorological and Other Instruments for Observatories, Travellers and Explorers, and the Army and Navy (London, 1896), p. 25.
Gloria Clifton, Directory of British Scientific Instrument Makers
1550-1851 (London, 1995), pp. 51-52.