W THE 23RD LETTER OF THE ALPHABET. This letter, as its name implies, was the letter u or v, which were identical till comparatively recent times, doubled and used by the Norman scribes to represent the English bilabial spirant (modern w), which had previously been represented in the Saxon hands by a Runic letter. The sound did not occur in the Romance languages. Latin had possessed it, but it had passed in imperial times into the voiced labial spirant (mod em v). A separate symbol was thus required to represent the Eng lish sound, and the French preferred the doubling of one of their own letters to the use of the Rune. (B. F. C. A.) WA, a tribe inhabiting north-east Burma, between the Salwin River and the state of Keng-Tung. They claim to be autoch thonous and may represent the aborigines of northern Siam and of Indo China; old records and travellers (e.g., McLeod in 1837) speak of them as the original inhabitants. Their village sites are still found covered with jungle. The people are short and dark, and may have Negrito blood in them, though speaking a Mon Khmer language. They are popularly divided into wild and tame.
The wild Wa are head-hunters. Outside every village is an avenue of huge oaks. Along one side is a line of posts facing towards the path with skulls fitted into niches, cut sometimes in front some times behind the post, when there is a hole in front, through which the skull is visible. Skulls must be added annually if the crops are to be good; those of distinguished and pious men are the most efficacious, and head-hunting (q.v.) takes place during the sowing season. Villages are high on the slopes of hills, usually on a knoll or spur. The only entrance is through a tunnel 3o to zoo yards long, of which there are usually two at opposite sides of the vil lage, about 5ft. high, and so narrow that two persons cannot pass freely, sometimes winding slightly to prevent gun-fire ; the path is studded with pegs to prevent a rush. Tattooing is occasional
only ; divination is performed with chicken-bones; dogs are eaten; polygamy is permitted, monogamy prevails and the tame Wa have five clans presumably exogamous.
See Scott & Hardiman, Gazetteer of Upper Burma, etc. (1900). WAALS, JOHANNES DIDERIK VAN DER (1837 1923), Dutch physicist, was born at Leyden Nov. 23, 1837. He was a self-taught man who took advantage of the oppor tunities offered by the university of Leyden. He first attracted notice in 1873 with his treatise Over de continuiteit van den gas-en vloeistoftoestancl (On the continuity of the gaseous and liquid state), by which he gained his doctor's degree. He taught physics at various high schools, and in 1877 he was appointed professor of physics in the university of Amsterdam, a post which he retained until 1907. Van der Waals built up a kinetic theory of the fluid state, he combined the determination of cohesion in Laplace's theory of capillarity with the kinetic theory of gases, and this led to the conception of the continuity of the liquid and gaseous states. Using this as a starting point he arrived at an equation of state which gave an explanation of critical phenomena and fitted in very well with the experimental observations of Andrews on carbon dioxide. Continuing this work he tried to arrive at an equation which would be the same for all substances. He event ually did this by using the values of the volume, temperature and pressure divided by their critical values. This led van der Waals to his statement of the "law of corresponding states" which enabled Dewar and Onnes to determine the necessary data in the liquefaction of the permanent gases. He also discovered the law of binary mixtures. In 1910 van der Waals was awarded the Nobel Prize for physics. He died on March 9, 1923.