Petty’s Maps were printed in 1685, two years before his death, as “Hiberniæ Delineatio quoad hactenus licuit perfectissima;” a collection of thirty-six maps, with a portrait of Sir William Petty, a work answering to its description as the most perfect delineation of Ireland that had up to that time been obtained. There is a coloured copy of Petty’s maps in the British Museum, and also an uncoloured copy, with the first five maps varying from those in the coloured copy, and giving a General Map of Ireland, followed by Maps of Leinster, Munster, Ulster, and Connaught. There was afterwards published in duodecimo, without date, “A Geographical Description of ye Kingdom of Ireland, collected from ye actual Survey made by Sir William Petty, corrected and amended, engraven and published by Fra. Lamb.” This volume gives as its contents, “one general mapp, four provincial mapps, and thirty-two county mapps; to which is added a mapp of Great Brittaine and Ireland, together with an Index of the whole.” At the Restoration William Petty accepted the inevitable change, and continued his service to the country. He was knighted by Charles the Second, and appointed in 1661 Inspector-General of Ireland. He entered Parliament. He was one of the first founders of the Royal Society, established at the beginning of the reign of Charles the Second; and the outcome of these scientific studies along the line marked out by Francis Bacon, which had been actively pursued in Oxford and at Gresham College. In 1663 he applied his ingenuity to the invention of a swift double-bottomed ship, that made one or two passages between England and Ireland, but was then lost in a storm.