David J. Rankin, explorer, lexicographer and gold prospector, was active in central Mozambique and southern Malawi during the eighteen-eighties. His explorations were reported in several papers in geographical journals, namely "Journey from Blantyre to Quillimane" (1885) and "The Chindi River and Zambezi Delta" (1890) in the Proceedings of the Royal Geographical Society; and "The Zambezi Delta" (1889), "Explorations in the Loangwa-Zambezi basin" (1892), and "The people and commercial prospects of the Zambezi basin" (1893) in the Scottish Geographical Magazine. A more comprehensive account of his travels and observations in East Africa was published in a book, The Zambezi basin and Nyassaland (Edinburgh, 1893, with maps).
During his investigation of the Zambesi delta in 1889 Rankin discovered a navigable channel north of the main mouths of the river which much facilitated the entrance into the river of vessels from the sea. It became known as the Chinde mouth and, though for the most part narrow and winding, had a minimum depth at the mouth of about two meters.
During his early years in East Africa Rankin collected material for a lexicographical work: Arab tales translated from the Swahili language into the Tugulu dialect of the Mákua language, as spoken in the immediate vicinity of Mozambique; together with comparative vocabularies of five dialects of the Mákua language (London, 1886, 46p). The Mozambique referred to in the title is not the country of that name, but a place on its coast in latitude 15şS.
Later Rankin wrote up his experiences as a prospector in Prospecting for gold; a handbook of practical information and hints for prospectors based on personal experience (London, 1901, 184p).