David Ferguson’s mineral prospecting expeditions to South Georgia (1912), the Falkland Islands and the South Shetland Islands (1913–1914), on behalf of the Christian Salvesen whaling company of Leith and now largely forgotten, were early examples of commercially motivated terrestrial exploration in the South Atlantic region. Prior geological knowledge was very limited and Ferguson complemented his unsuccessful prospecting work with attempts to understand the regional geology of the areas that he visited. These interpretations were based on relatively cursory fieldwork undertaken in an arduous environment, and did not prove robust; but the well-documented specimen collections that Ferguson accumulated provided the basis for excellent and much-cited petrographical accounts by G. W. Tyrrell of Glasgow University. Ferguson had studied geology at the university and the influence of his mentor there, Professor J. W. Gregory, is apparent. In turn, Gregory utilized Ferguson’s observations in support of a subsided ‘South Atlantic continent’, opposing the ‘displacement hypothesis’ for that region formalized by Alfred Wegener from 1912 onwards. Ferguson’s field notebooks and most of his rock specimens are now held by Glasgow University (Archive Services and Hunterian Museum, respectively) but he distributed representative specimen collections widely, and these are extant in several other British museums. Specimens were also supplied to, and discussed with, William Speirs Bruce who, following the 1902–1904 Scottish National Antarctic Expedition, took a keen interest in Ferguson’s discoveries.