Johnston was appointed a royal commissioner to report on the fisheries of Tasmania, also did much geological work, and in 1888 the government published his "Systematic Account of the Geology of Tasmania".
Johnston was appointed a royal commissioner to report on the fisheries of Tasmania, being the author of "Descriptive Catalogue of Tasmanian Fishes" (Hobart, 1882). Johnston also did much geological work, and in 1888 the government published his "Systematic Account of the Geology of Tasmania".