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.

In 1670 Sir William Petty established on his lands at Kerry the English settlement at the head of the bay of Kenmare.  The building of forty-two houses for the English settlers first laid the foundations of the present town of Kenmare.  “The population,” writes Lord Macaulay, “amounted to a hundred and eighty.  The land round the town was well cultivated.  The cattle were numerous.  Two small barks were employed in fishing and trading along the coast.  The supply of herrings, pilchards, mackerel, and salmon, was plentiful, and would have been still more plentiful had not the beach been, in the finest part of the year, covered by multitudes of seals, which preyed on the fish of the bay.  Yet the seal was not an unwelcome visitor:  his fur was valuable; and his oil supplied light through the long nights of winter.  An attempt was made with great success to set up ironworks.  It was not yet the practice to employ coal for the purpose of smelting; and the manufacturers of Kent and Sussex had much difficulty in procuring timber at a reasonable price.  The neighbourhood of Kenmare was then richly wooded; and Petty found it a gainful speculation to send ore thither.”  He looked also for profit from the variegated marbles of adjacent islands.  Distant two days’ journey over the mountains from the nearest English, Petty’s English settlement of Kenmare withstood all surrounding dangers, and in 1688, a year after its founder’s death, defended itself successfully against a fierce and general attack.

Sir William Petty died at London, on the 16th of December, 1687, and was buried in his native town of Romsey.  He had added to his great wealth by marriage, and was the founder of the family in which another Sir William Petty became Earl of Shelburne and first Marquis of Lansdowne.  The son of that first Marquis was Henry third Marquis of Lansdowne, who took a conspicuous part in our political history during the present century.

Sir William Petty’s survey of the land in Ireland, called the Down Survey, because its details were set down in maps, remains the legal record of the title on which half the land in Ireland is held.  The original maps are preserved in the Public Record Office at Dublin, and many of Petty’s MSS. are in the Bodleian Library at Oxford.