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Rh Hindustan and the history of their uses among the native races. The results of these investigations appeared in an essay On the Antiquity of Hindoo Medicine (1837). For nearly ten years he held the post of superintendent of the East India Company's botanic garden in the Himalayas at Saharanpur. In 1837 he was appointed to the professorship of materia medica in King's College, London, which he held till 1856. From 1838 onwards he conducted a special department of correspondence, relating to vegetable products, at the East India House, and at the time of his death he had just completed there an extensive and valuable museum of technical products from the East Indies. In 1851 he superintended the Indian department of the Great Exhibition. He died at Acton near London on the 2nd of January 1858.

ROYSTON, a market town in the Hitchin parliamentary division of Hertfordshire, England, close to the border of Cambridgeshire, 48 m. N. of London by the Cambridge branch of the Great Northern railway. Pop. of urban district (1901) 3517. The church of St John the Baptist is mainly Early English. There are a market house, and institute with library and museum. Beneath a street in the town is a curious example of a hermit’s cave, excavated in the chalk, and containing rude carvings of the crucifixion and other sacred subjects. It was discovered in 1742. The town lies on the Roman Ermine Street, at the point where it strikes from the hills across the plain, and its straight course is deflected slightly W. Roman relics have been found, and several barrows and earth-mounds occur on the neighbouring hills. A monastery of Augustinian canons was founded here towards the close of the 12th century, but there are no remains.

 ROYTON, an urban district of Lancashire, England, within the parliamentary borough of Oldham, 2 m. N. of Oldham on the Lancashire & Yorkshire railway. Though of early origin, it is, as a town, of wholly modern growth. The cotton manufacture is its chief industry. Pop. (1901) 14,881.

 ROZAS, JUAN MARTINEZ DE (1759–1813), the earliest leader in the Chilean struggle for independence, was born at Mendoza in 1759. In early life he was a professor of law, and of theology and philosophy at Santiago. He held the post of acting governor of Concepcion at one time, and was also colonel in a militia regiment. In 1808 he became secretary to the last Spanish governor, Francisco Antonio Carrasco, and used his position to prepare the nationalist movement that began in ISOQ. After resigning his position as secretary, Rozas was mainly responsible for the resignation of the Spanish governor, and the formation of a national ]unta on the 18th of September ISIC, of which he was the real leader. Under his influence many reforms were initiated, freedom of trade was established, an army was organized and a national congress was called together in July 1811. But at the end of that year divisions began to arise between Rozas' followers from Concepcién and the men of Santiago; and a feud broke out between Rozas and (q.v.) who had secured control of Santiago. In 1812 Carrera succeeded in securing the banishment of his rival, who retired to Mendoza, where he died on the 3rd of March 1813.

See P. B. Figueroa, Diccionario biográfico de Chile, 1550–1887 (Santiago, 1888), and J. B. Suarez, Rasgos biográficos de hombres notables de Chile (Valparaiso, 1886); both giving biographical sketches of prominent characters in Chilean history.

RUABON (Rhiwabon), a town of Denbighshire, N. Wales, in the E. parliamentary division, near the Shropshire border, 5 m. S.W. of Wrexham, on the Great Western railway. Pop. (1901) 3248. It is situated on a small tributary of the Dee. The old Gothic church is thought by some to have been founded by Mabon, a brother of Llewelyn (13th c.), and has monuments to the Wynn family, by Nollekens and Rhysbrac, and to Dr D. Powel (d. 1598), translator into English of Caradoc’s (of Llancarfan) History of Wales. In the neighbourhood are collieries, engineering works, an iron foundry and chemical works, besides an extensive industry in glazed and other bricks. Near Ruabon is Caerdden (Caerddin), an ancient camp (village) surrounded by circular entrenchments, and Wynnstay, with an avenue of fine trees. Anciently the residence of Madoc ab Gruffyd Maelor (founder of Valle Crucis Abbey), it was called Wattstay, from Watt’s Dyke, an old rampart on the estate. It was named Wynnstay on its coming into possession of the Wynns (17th c.). Offa’s Dyke, near here, is 10 ft. high, and broad enough for two carriages abreast. Not far is Chirk Castle (supposed to have been built in 1013), besieged by Cromwell’s artillery: near it, in the Ceiriog valley, the defeat of Henry II. by Owen Gwynedd took place in 1165.

 RUBBER, or  (a word probably derived from Cahucha or Caucho the names in Ecuador and Peru respectively for rubber or the tree producing it), the chief constituent of the coagulated milky juice or latex furnished by a number of different trees, shrubs and vines. The latex of the best rubber plants furnishes from 20 to 50% of rubber. The latex is not to be confused with the sap of trees, on the circulation of which their nutrition depends. Though frequently occurring, it is not a universal feature of plant life, and does not appear to be necessary or even directly connected with the nutritive system of plants. Its exact function is not fully understood. Latex, though chiefly secreted in vessels or small sacs which reside in the cortical tissue between the outer bark and the wood is also found in the leaves and sometimes in the roots or bulbs. The trees and plants whose latices furnish caoutchouc in considerable quantity chiefly belong to the natural orders Euphorbiaceae, Urticaceae, Apocynaceae, Asclepiadaceae. The latex is usually obtained from the bark or stem by ma-king an incision reaching almost to the wood when the milky fluid flows more or less readily from the laticiferous vessels. It is, like milk, an emulsion, and when examined with the microscope is seen to consist"of numerous globules suspended in a watery fluid. On standing, some latices separate, more or less readily, into an upper layer resembling cream and consisting of the globules, and a lower watery layer. This separation can be rapidly effected with some latices by the use of a centrifugal machine, but this method has not yet been applied to any extent commercially. The globules which furnish the cream gradually pass on standing into solid caoutchouc, a process which is facilitated by rapid stirring, or by the addition of an acid or other chemical agent. If the latex is warmed or an acid, an alkali or astringent 'plant juice is added to it, “coagulation” usually takes place more or less readily, the caoutchouc separating in solid flakes or curds. The efficacy of heat or of an acid, an alkali or other agent in promoting coagulation depends on the character of the latex, and varies with that obtained from different plants. The watery fluid in which the globules are suspended holds certain proteids, carbohydrates and a small proportion of salts in solution. The latex exhibits a neutral, acid or alkaline reaction depending upon the plant from which it has been obtained.

When exposed to air the latex gradually undergoes putrefactive changes accompanied by coagulation of the caoutchouc. The addition of a small quantity of ammonia or of formalin to some latices usually has the effect of preserving them for a considerable time. The nature of the coagulation is not yet completely understood. It has been compared with that of milk and of blood, which depend essentially on the coagulation or separation in curds of a proteid or albuminous substance, such as takes place when white of egg is warmed. There is, however, reason to believe that the coagulation of latex into rubber is not mainly of this character. The globules in the latex are liquid, and the phenomenon of coagulation would seem to consist in the passage of this liquid into solid caoutchouc through the kind of change known as polymerization or condensation, in which a liquid passes into solid without alteration