teen years he spent most of his time in the jungle and on the plains of Bengal. The huge amount of map material he collected was used in the preparation of the Bengal Atlas, which appeared in I779, a work of the first importance for strategical and administrative purposes. His map of Hindustan, accompanied by about 200 pages of letterpress, appeared in 1783, and marked the time when Rennell ceased to be merely a surveyor and map-maker and became a geographer in the more extended sense. Rennell lived for the remainder of his life in London, and for fifty years, from 1780 to 1830, he was one of the leading geographers of Europe, and the great critic of geographical work and elucidator of geographical problems. Comfortably established with his wife and children in London, he began the construction of the first approximately correct map of India, and many years elapsed before it was superseded by the more accurate trigonometrical survey. He then turned his attention to Western Asia between India and the Mediterranean. He had conceived a scheme for a great work on the comparative geography of Western Asia, but he never completely carried it out, his Geography of Herodotus, which formed only a part of the whole project, occupying him for many years. This work has been of permanent value to geographical students.
Rennell's studies of Herodotus made him a very high authority on all matters relating to African geography, and he became the coadjutor of the African Association when that body inaugurated the modern era of the exploration of that continent. His map of Northern Africa, prepared for the use of the association, was the result of immense research combined with sagacious reasoning. He elucidated the reports of explorers, and his maps illustrated their travels. He worked up. for example, the rough notes of Mungo Park, examined his daily routes with great care, compared them critically with previous work in West Africa, and brought all the materials into harmony as far as possible. He constructed the map of the discoveries of Mungo Park. As a hydrographer, also, Rennell made important advances in the study of winds and currents, and was the founder of that branch of geography which is now called oceanography. Rennell's volume on winds and currents is based upon an enormous mass of material which he collected to illustrate the subjects. The current now known as Rennell's current, a stream in the ocean moving northward athwart the mouth of the English and Irish channels, was revealed by his study of a great number of facts collected by seamen. His wind and current charts, published only after his death, contained a large amount of information of service to mariners. His body was buried in Westminster Abbey.
RENNES, ren. The capital of the Department of Ille-et-Vilaine. France, at the confluence of the rivers Ille and Vilaine, 155 miles east of Brest by rail (Map: France, E 3). It is divided into the upper or new town and the lower or old town. It has remains of its mediæval walls, towers, and gates, beyond which lie extensive suburbs. Bridges unite the two divisions of the town, the older portions of which lie on the left bank of the quay-lined Vilaine. The most noteworthy buildings are the modern cathedral, whose interior is a spacious hall of Grecian architecture, the stately Palais de Justice, the Hôtel de Ville, the Lycée, the Palais Universitaire with its fine art museum, and the handsome modern university. Tree-lined boulevards, the spacious Champ-de-Mars with a war monument commemorating 1870-71, and the Jardin des Plantes, add to the town's attractions. It carries on an active trade and has manufactures of agricultural implements, stockings, lace, sail-cloths, and earthenware. The town is the seat of an archbishopric and of a university, which has an attendance of about 1150. It was almost totally destroyed by a great fire in 1720, and was rebuilt on a modern plan. Rennes is the Celtic Condate, the capital of the Gallic tribe of the Redones, whence the modern mime. Under the Romans it was an important station. In the Middle Ages it was the capital of the Duchy of Brittany (q.v.). Population, in 1901, 74,676.
RENNET (from ME. rennen, rinnen, AS. rinnan, yrnan, Goth., OHG. rinnan, Ger. rinnen, to run; connected with Lat. rivus, stream, Skt. ar, to move). A substance obtained from the fourth or digestive stomach of calves living upon milk, and also from the stomachs of puppies and pigs. The active principle is obtained from the folds of the membrane lining the stomach, and is prepared commercially by soaking this lining in warm slightly salted water, filtering the resulting extract, and adding a little salt and saltpetre to preserve it. These extracts are generally used in place of the home-made preparations formerly in use. They are of uniform strength, free from taints, and retain their strength and purity for a considerable time. The active principle, rennin, an enzyme or ferment, has the power of coagulating or curdling the casein of milk. The extracts also contain more or less pepsin, the digestive ferment of the stomach. The action of rennet is impaired by heat, and the ferment is destroyed by high heat. The principal use of rennet or rennet extract is in making cheese, where it is employed to curdle the milk, and thus form the curd. See Cheese-making.
REN'NIE, George (1791-1866). An English civil engineer. He was born in Surrey, the eldest son of John Rennie (q.v.), and at the ago of sixteen entered Edinburgh University. He returned to London in 1811, and began the practical study of engineering under his father. In 1818 he was appointed superintendent of the machinery of the mint, and at the same time aided his father in the planning and designing of several of his later works. After his father's death, in 1821, Rennie entered into partnership with his younger brother, John (afterwards Sir John Rennie), as engineer and machinery constructor. Their operations included the construction of bridges, harbors, docks, ship-yards, and dredging machinery, steam factories, both in Great Britain and on the Continent, and the furnishing of engines for warships of England, Russia, France, Italy, Mexico. etc. Rennie in addition was engaged in the drainage of large tracts in the midland counties of England and the construction of several Continental railways. He was greatly interested in the development of the screw propeller, and after building the engines for the Archimedes boat with a novel form of screw, constructed the Dwarf, the first screw vessel in the British Navy. He was the author of various papers published in the Philosophical Transactions.
