Two charts side by side of the Straits of Dryon and some islands in the Riau Archipelago with depth soundings. From a group of important charts, printed on 15 separate sheets, which were produced between September 1804 and May 1805 by the East India Company Hydrographer Alexander Dalrymple, as an accompaniment to his Memoir of a chart of the passages at the southern extremity of Asia (London, 1805).