Sir William Matthew Flinders Petrie

Sir William Matthew Flinders Petrie , 1853-1942, English archaeologist, a noted Egyptologist. He excavated ancient remains in Britain (1875-80), Egypt (1880-1924), and Palestine (1927-38) and was (1892-1933) professor of Egyptology at University College, London. In 1894 he founded the Egyptian Research Account, which became (1905) the British School of Archaeology in Egypt. His most important excavations were at Memphis, but he made many other outstanding discoveries. Among these are the sites of Greek settlements at Naucratis (1885) and Daphnae (1886); tombs of the first dynasty at Abydos (1899); the stele of Merneptah at Thebes (1896), inscribed with the earliest known Egyptian reference to Israel; and ruins of 10 cities at Tel-el-Hesy (S of Jerusalem). His writings include many works on ancient Egypt, Methods and Aims in Archaeology (1904), and Seventy Years in Archaeology (1931). He edited A History of Egypt (6 vol., rev. ed. 1923-27), of which he wrote the first three volumes. A tireless and meticulous excavator, Petrie was responsible for greatly advancing the methodology of archaeology. He was particularly innovative in the interpretation of deeply stratified deposits, undertaking the seriation of undecorated pottery and demonstrating how ceramics from Egypt could be used to establish the age of archaeological strata outside Egypt, a technique known as cross-dating.

magnetic compass, a compass which depends for its directive property on the horizontal component of the earth's magnetic field. Its origins are obscure and although the earliest references to its use at sea are Chinese (before 1050), there is no direct evidence that it came to the West from China, nor that Arab ships were instrumental in bringing it. The earliest recorded mention of its use in the West was in 1180, although there are grounds for thinking it was in use well before that. No one person has been credited with the invention of the magnetic compass but it is clear that, in the West, it first appeared in the Mediterranean (by local legend in Amalfi).

The forerunner of the modern magnetic compass consisted of a magnetized needle thrust into a straw or piece of cork which floated freely in a basin of water. On settling, the marked end of the needle indicated the direction of magnetic north. In later times a primitive pivoted needle or needle system was used to serve the same purpose, and later still a compass card, on which the points of the compass were drawn, was attached to a needle magnetized by the oxide of iron lodestone, and the whole was enclosed in a suitable bowl to afford protection, the bowl in turn being mounted in gimbals in a binnacle.

The magnetic compass was an imperfect instrument until after the time when the first iron ship appeared. The magnetism inherent in an iron ship's structure caused considerably difficulty in the early days, to such an extent that it was suggested seriously that such ships would never be successful for they would be quite unsafe in the absence of well-behaved compasses.

On wooden vessels the directive power of a magnetic compass is dependent, apart from relatively minor effects of ironwork fittings in its vicinity, on the earth's magnetism. Nevertheless, as far back as the beginning of the 19th century, Matthew Flinders, the British navigator and explorer, discovered that the compass needle might be deviated from the direction of magnetic north as a result of local attraction, as it was termed, of the ship's iron. He demonstrated that this deviation was at a maximum with ships' courses of east or west by compass and disappeared when a ship steered north or south. He also showed how the ship's magnetic effect could be neutralized by means of an unmagnetized rod of iron placed vertically near the compass. This form of corrector is still universally used and is named a Flinders bar.

With the advent of iron and steel ships, a great deal of study was directed to the nature of ship magnetism with the object of devising a method of neutralizing it at the compass position. Among those who engaged themselves in this important work was the Astronomer Royal, Sir G. B. Airy, who had the iron steamer Rainbow placed at his disposal in 1838. From his careful examination of the vessel's magnetic condition, he introduced a method of neutralizing a ship's magnetism by placing magnets and pieces of unmagnetized iron, or correctors, in the vicinity of the compass. To find what correctors are needed to neutralize a ship's magnetism it is necessary to swing every vessel fitted with a magnetic compass, including yachts.

See also Thomson, William.