Considered "one of the last true geological polymaths", Sollas worked in a number of areas including the study of sponges, brachiopods and petrological research, and during his lifetime published 180 papers and wrote three books. He also invented the serial sectioning device for the study of fossils. His biggest contribution at Oxford was in expanding the University geology department, hiring new Demonstrators and Lecturers and expanding the facilities available to students. Described as "eccentric" in his final years, he left much of the running of the Department to J.A. Douglas while he concentrated on research, finally dying in office on 20 October 1936.