the Rhone and the Saône. There are also iron and steel works where iron goods and ironmongery of all kinds are manufactured.
Rive-de-Gier is a place of some antiquity, as appears from remains of Gallo-Roman buildings, and mosaics and coins found at various times. In the time of Henry IV. the working of the mines had already given to the locality a measure of importance.
RIVER, any considerable stream of water flowing in a defined channel. The origin and subsequent formation of rivers and the valleys along which they flow are considered under
Geography, § Principles of Geography, and Geology, § viii. The word "river" is an adaptation of the O. Fr. rivere (mod. rivière), which descends through Med. Lat. rivera, Low. Lat. riparia, in the sense of river-bank and river, from ripa, bank. The Latin for a stream or river is rivus, whence rivulas, a small
stream, Eng. "rivulet," which is, therefore, distinct in origin
from "river," though probably the sense of rivus influenced
the Med. Lat. rivera. The etymology of rivus and ripa is disputed; some scholars refer both to the root ri-, to drop, flow; others take ripa to be from the root seen in Gr. ἐρείπειν, to tear, English "rive," the sense being a broken cliff or steep bank.
RIVER BRETHREN, the name of a group of three Christian
communities in the United States of America, descended from
Swiss settlers near the Susquehanna river in Pennsylvania in
1750. The first pastor was Jacob Engle, who became head of
the community in 1770. Their system is based on literal
obedience to the commands of the New Testament, and they
have points of similarity both with the Mennonites and with
the Dunkards. They practise foot-washing and baptism by trine immersion; are strict sabbatarians and simple in their manner of life. The three branches are: (1) The Brethren in Christ, who are the most elaborately organized and are numerous in Ohio, Pennsylvania and Kansas; they have also formed churches in New York and in Canada, and missions in South Africa, India and Texas. In 1909 they had 174 ministers, and 65 churches with 3675 communicants. (2) The Old Order, or Yorker Brethren, consists of a small body which separated from the main body in 1843 and maintained more strictly the original practice. They are found specially in York county, Pennsylvania (whence the name "Yorkers"). In 1909 they had 24 ministers, 9 churches, and 423 communicants. (3) The United Zion's Children date from 1853,
when a small body left the parent communion on minor questions
of administration. They had in 1909 22 ministers and 28
churches with 749 communicants, all in Pennsylvania.
RIVER ENGINEERING. Before undertaking works for the
improvement of rivers, either with the object of mitigating the
effects of their inundations, or for increasing and extending their capabilities for navigation, it is most important that their physical characteristics should be investigated in each case, for these vary greatly in different rivers, being dependent upon the general configuration of the land, the nature of the surface strata and the climate of the country which the rivers traverse.
Physical Characteristics of Rivers
The size of rivers above any tidal limit and their average freshwater discharge are proportionate to the extent of their basins, and the amount of rain which, falling over these basins, reaches the river channels in the bottom of the valleys, by which it is conveyed to the sea.
River Basins.—The basin of a river is the expanse of country, bounded by a winding ridge of high ground, over which the rainfall flows down towards the river traversing the lowest part of the valley; whereas the rain falling on the outer slope of the encircling ridge flows away to another river draining an adjacent basin. River basins vary in extent according to the configuration of the country, ranging from the insignificant drainage-areas of streams rising on high ground very near the coast and flowing straight down into the sea, up to immense tracts of great continents, when rivers, rising on the slopes of mountain ranges far inland, have to traverse vast stretches of valleys and plains before reaching the ocean. The size of the largest river basin of any country depends on the extent of the continent in which it is situated, its position in relation to the hilly regions in which rivers generally rise and the sea into which they flow, and the distance between the source and the outlet of the river draining it.
Great Britain, with its very limited area, cannot possess large river basins, its largest being that of the Thames with an area of 5244 sq. m. Even on the mainland of Europe, river basins augment in extent on proceeding eastwards with the increasing width of the continent; in France the largest basin is that of the Loire with an area of 45,000 sq. m., while the Rhine has a basin of 86,000 sq. m. with a length of 800 m., the Danube a basin of 312,000 sq. m. with a length of 1700 m., and the Volga a basin of 563,000 sq. m. with a length of 2000 m. The more extensive continents of Asia, Africa and North and South America possess still larger river basins, the Obi in Siberia having a basin of about 1,300,000 sq. m. and a length of 3200 m., the Nile a basin of 1,500,000 sq. m. with a length of over 4000 m., and the Mississippi, flowing from north to south, having a basin of 1,244,000 sq. m. with a length of 4200 m. The vast basin of the Amazon of 2,250,000 sq. m. is due to the chain of the Andes almost bordering the Pacific coast-line, so that the river rising on its eastern slopes has to traverse nearly the whole width of South America at its broadest part before reaching the Atlantic Ocean.
Available Rainfall.—The rainfall varies considerably in different localities, both in its total yearly amount and in its distribution throughout the year; also its volume fluctuates from year to year. Even in small river basins the variations in rainfall may be considerable according to differences in elevation or distance from the sea, ranging, for instance, in the Severn basin, with an area of only 4350 sq. m., from an average of under 30 in. in the year to over 80 in. The proportion, moreover, of the rain falling on a river basin which actually reaches the river, or the available rainfall in respect to its flow, depends very largely on the nature of the surface strata, the slope of the ground and the extent to which it is covered with vegetation, and varies greatly with the season of the year. The available rainfall has, indeed, been found to vary from 75% of the actual rainfall on impermeable, bare, sloping, rocky strata, down to about 15% on flat, very permeable soils.
Fall of Rivers.—The rate of flow of rivers depends mainly upon their fall, though where two rivers of different sizes have the same fall, the larger river has the quicker flow, as its retardation by friction against its bed and banks is less in proportion to its volume than that of the smaller river. The fall of a river corresponds approximately to the slope of the country it traverses; and as rivers rise close to the highest part of their basins, generally in hilly regions, their fall is rapid near their source and gradually diminishes, with occasional irregularities, till, in traversing plains along the latter part of their course, their fall usually becomes quite gentle. Accordingly, in large basins, rivers in most cases begin as torrents with a very variable flow, and end as gently flowing rivers with a comparatively regular discharge.
Variations in the Discharge of Rivers.—The irregular flow of rivers throughout their course forms one of the main difficulties in devising works, either for mitigating inundations or for increasing the navigable capabilities of rivers. In tropical countries, subject to periodical rains, the rivers are in flood during the rainy season and have hardly any flow during the rest of the year; whilst in temperate regions, where the rainfall is more evenly distributed throughout the year, evaporation causes the available rainfall to be much less in hot summer weather than in the winter months, so that the rivers fall to their low stage in the summer and are very liable to be in flood in the winter. In fact, with a temperate climate, the year may be divided into a warm and a cold season, extending from May to October and from November to April respectively; the rivers are low and moderate floods are of rare occurrence during the first period, and the rivers are high and subject to occasional heavy floods after a
