Dudley Adams was a maker of scientific instruments in London, England, during the late 18th and early 19th centuries.17 He was one of many instrument makers during this time period that made theodolites, most notably of whom include Jesse Ramsden.4 The theodolite was a precision optical instrument—essentially a small telescope—that was used on voyages to locate accurate star positions. Dudley’s theodolite was most likely used for the ship given that it has a tripod mounting socket attached to the underside of the base plate, which would have allowed the instrument to be oriented in the azimuth about its spindle.18 The telescope can also be pulled up and down. This, along with the mounting socket, allowed full range of rotation for accurate observations. There is a compass in the center of the theodolite for orientation of direction. A ship was not the only place for a theodolite, as they were also used in tent observatories. On Matthew Flinders circumnavigation of Australia from 1801-1803, he used Ramsdens Universal Theodolite in conjunction with Hadley’s sextant and Earnshaw’s Astronomical Clock to determine the longitude by the lunar method, which he then used to check the “going rate of the clocks” while in the tent observatory.2