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Rh in the royal navy. He went abroad again in 1643, and remained for three years in France and the Netherlands, pursuing his, studies. In Paris he read Vesalius with Hobbes, who was then preparing his Tractatus opticus, and it is said that Petty drew the diagrams for him In 1647 Petty obtained a patent for the invention of double writing, i.e. a copying machine. In politics he espoused the side of the parliament. His first publication was a letter to Samuel Hartlib in 1648, entitled Advice for the Advancement of some Particular Parts of Learning, the object of which was to recommend such a change in education as would give it a more practical character. In the same year he took up his residence at Oxford, where he was made deputy professor of anatomy, and where he gave instruction in that science and in chemistry. In 1649 he obtained the degree of doctor of physic, and was soon after elected a fellow of Brasenose College. He gained some notoriety in 1650 by restoring to life a woman who had been hanged for infanticide. In 1651 he was made professor of anatomy at Oxford, and also became professor of music at Gresham College. In 1652 he went to Ireland, having been appointed physician to the army in that country. In 1654, observing that the admeasurement and division of the lands forfeited in 1641 and granted to the soldiers had been "most inefficiently and absurdly managed," he entered into a contract to execute a fresh survey, which he completed in thirteen months. By this he gained £9000, and part of the money he invested profitably in the purchase of soldiers' debentures. He thus became possessor of so large a domain in the county of Kerry that, according to John Aubrey, he could behold from Mt Mangerton 50,000 acres of his own land. He set up ironworks in that neighbourhood, opened lead-mines and marble quarries, established a pilchard fishery, and commenced a trade in timber. Besides the office of commissioner of distribution of the lands he had surveyed, he held that of secretary to the lord-lieutenant, Henry Cromwell, and was also during two years clerk of the council. In January 1658 he was elected to Richard Cromwell's parliament as member for West Looe in Cornwall. After the Restoration he returned to England and was favourably received and knighted by Charles II, who was "much pleased with his ingenious discourses," and who, it is said, intended to create him earl of Kilmore. He obtained from the king a new patent constituting him surveyor-general of Ireland. In 1663 he attracted much notice by the success of his invention of a double-bottomed ship, which twice made the passage between Dublin and Holyhead, but was afterwards lost in a violent storm. He was one of the first members of the Royal Society, and sat on its council. He died in London on the 16th of December 1687, and was buried in the church of his native place. His will, a curious and characteristic document, is printed in Chalmers's Biographical Dictionary.

His widow, Elizabeth (d. 1708), daughter of Sir Hardress Waller (1604–1666), the Irish Cromwellian soldier and regicide, was created Baroness Shelburne by James II. in 1688; and her two sons were successively created earls of Shelburne, but on their death without issue the Petty estates passed to their sister, Anne, and after her marriage to the 1st earl of Kerry the Shelburne title was revived in her son's favour (see under ).

Petty's Irish survey was based on a collection of social data which entitles him to be considered a real pioneer in the science of comparative statistics. He was also one of the first in whom we find a tendency to a view of industrial phenomena which was at variance with the then dominant mercantilism ideas, and he exhibits a statesmanlike sense of the elements in which the strength of a nation really consists. Roscher names him as having, along with Locke and Dudley North, raised the English school to the highest point it attained before the time of Hume. His Treatise of Taxes and Contributions contains a clear statement of the doctrine that price depends on the labour necessary for production. Petty is much concerned to discover a fixed unit of value, and he thinks he has found it in the necessary sustenance of a man for a day. He understands the cheapening effect of the division of labour. He states correctly the notion of "natural and true" rent as the remainder of the produce of land after payment of the cost of production, but he seems to have no idea of the "law of diminishing returns." He has much that is just on the subject of money: he sees that there may be an excess of it as well as a deficiency, and regards the prohibition of its exportation as contrary to sound policy. But he errs in attributing the fall of the rate of interest which takes place in the progress of industry to the increase in the quantity of money He protested against the fetters imposed on the trade of Ireland, and advocated a union of that country with Great Britain Whilst the general tendency in his day was to represent England as in a state of progressive decline—an opinion put forward particularly in the tract entitled Britannia languens—Petty declared her resources and prospects to be not inferior to those of France.

A complete list of his works is given in the Athenae oxonienses. The most important are: the Treatise of Taxes and Contributions (1662, 1667 and 1685); Political Arithmetic, presented in MS. to Charles II., but, because it contained matter likely to be offensive to France, kept unpublished till 1691, when it was edited by Petty's son Charles; Quantulumcunque, or a Tract concerning Money (1682), Observations upon the Dublin Bills of Mortality in 1681 and the State of that City (1683); Essay concerning the Multiplication of Mankind (1686); Political Anatomy of Ireland (1691). Several papers appeared in the Philosophical Transactions. See Economic Writings of Sir William Petty, ed. C. H. Hull (2 vols., 1899).

PETTY-OFFICER, the title in the navy of a large number of minor (Fr. petit, small) officers, of less than commissioned or warrant rank-such as the master-at-arms, sail maker, caulker, armourer, cook, &c. They were originally named, and removable, by the captain.

 PETUNIA, in botany, a genus of plants belonging to the natural order Solanaceae and containing about 16 species, chiefly South American (southern Brazil and Argentina). The garden forms are derived from the white-flowered P. nyctaginiflora and the violet- or purple-flowered P. violacea. The varieties of petunia, especially the double forms, make admirable specimens for pot culture.

Named or specially fine varieties are propagated by cuttings taken from stock plants kept through the winter on a dry warm shelf, and moved into a brisk moist heat in early spring; the young shoots are planted in pans or pots filled with sandy soil, and, aided by a brisk bottom heat, strike root in a few days. They are then potted singly into thumb-pots and when once established are gradually hardened off, and afterwards repotted as required. The shoots should be topped to make bushy plants, and their tops may be utilized as cuttings. The single varieties are raised from seeds sown in light sandy soil in heat, in the early spring, and very slightly covered. The plants need to be pricked out or potted off as soon as large enough to handle. Good strains of seeds supply plants suitable for bedding; but, as they do not reproduce themselves exactly, any sorts particularly required must be propagated, like the double ones, from cuttings.

 PETWORTH, a market town in the Horsham parliamentary division of Sussex, England, 55 m. S.S.W. from London by the London, Brighton & South Coast railway. Pop. (1901), 2503. The church of St Mary is Perpendicular, and contains numerous memorials of members of the Percy family and others. Petworth House, situated in a beautiful park, dates from the 18th century, and contains a magnificent collection of pictures. At Bignor in the neighbourhood are remains of an important and splendidly adorned Roman villa.

The first mention of Petworth (Peartingawyrth, Petered, Puetewird, Pedewurde, Putteworth, Pytteworth, Petteworth) occurs in a grant by Eardwulf, king of Northumbria, to St Peter's Church, about 791. In the time of Edward the Confessor Petworth was an allodial manor held by his queen Edith, and in 1086 Robert Fitz-Tetbald held it of Roger Montgomery, earl of Shrewsbury. It then included a church and a mill, and was rated at nine hides. Through Queen Adelisa, Petworth came first into the hands of 