PLAIN. 86 to wander, OHG. flah, Oct. flach, flat. OlIG. i:(i(o/-, i;cr. riur, AS. /lor, Kng. floor, Olr. I<ir, lloor). An expanse of level or {.'ently sloping land. In contrast with a plateau, the surface of a plain is disposed at a low elevation, generally less than 1000 feet, altliou{;li no sharp line of division can be drawn between the two. The tJreat Plains of the Initcd States have an eleva- tion on the western border of 2000 feet or more. In respect to their origin, plains may be classed as marine, lacustrine, lluviatilc, and plains of denudation. Marine plain/) are formed by the deposition of sediment beneath the sea. The dfbris brought down by rivers to their mouths is carried .seaward by tides and currents and dis- tributed over a wide area. Thus in time a broad belt of sedimentary strata accumulates along the margins of continental lands, and these sediments may subsequently be raised into laud. The Coastal Plain (q.v. ) which extends along the Atlantic and Gulf Ixnders of the United States and the North German Plain have been formed in this manner. The marine origin may be demiinstratcd by the character of the fossils in- cluded in the strata. Lncuxtrinc plains occupy the basins of former lakes whose disappearance may have been brought about in various ways. The celebrated Vale of Kashmir in Xorthwestern India and the great Hungarian Plain are covered with fine sediments that were deposited in bodies of fresh water before the outlets had been cut down. In Nevada and Utah there arc extensive lacustrine plains which have been laid bare owing to a change of climate from moist to arid condi- tions, and similar plains are known to occur in Central Asia. A peculiar type is that illustrated by the valley of the Red River of the North; during the Glacial jieriod a great lake was formed here only to disappear with the retreat of the obstructing ice-sheet. (See Lake, Lake Agas- siz.) Fluviatile plains are built up by the depo- sition of silt alo_ng the borders and at the nmuths of rivers. The Mississippi, the Nile, the liangcs, and most of the large rivers of the world have constructed extensive fluviatile plains. (See Flood-Plain; Delta.) Plains of denudation owe their origin to erosion. When land has acquired considerable elevation above the sea the surface is dissected by the action of running streams which are constantly engaged in widen- ing and deepening their channels. This process when carried to completion results in the reduc- tion of the divides between the streams, produc- ing a broad lowland whose surface lies but little above sea level. If the former elevations are still indicated by unconsumed hills the lowland is called a peneplain. The plain thus produced may again be elevated and once more subjected to the process of dissection and base-leveling. The great plain of Central Russia and the lowlands border- ing the Appalachians have probably been formed in this way. See Geooraphy; Phy.siography. PLAIN,. The. In the history of the French Revolution, the moderate party in the Legisla- tive Assembly and Convention, so called in con- tradistinction from the Mountain (see Mont.g- NARDS ) . PLAIN CHANT. A term applied to the ec- clesiastical chant of the Roman Catholic Church. Tliis style of music was used in the Church from the earliest times. It has certain characteristics which distinguish it from any other known music. PLAIN CHANT. All the melodies have a stateliness and quiet dig- nity rendering them particularly appropriate lor the use of the Church. The tempo is moderate, and each melody is written in one of those tonali- ties known as the Church modes. (See JIouES.) For the notation a statt' of four lines is used, and the notes arc all black and square or lozenge- shaped. For the history and development of this system of ])lain chant notation, see Mexsub.*.ble .MU.SIC and MisitAL Notation. The origin of plain chant has been the subject of much speculation, but the best authorities now agree that it seems exceedingly proliable that the chants of the early Christian Chvirch were either taken directly from or modeled after those of the Hebrews. This .supposition is borne out by the information we possess regarding the performance of the nnisic during the first three centuries of the Christian Era; for the singing was antiphonal, i.e. a precentor intoned the mel- ody and the chorus answered. We have the tes- timony of Pliilo, a Hebrew writer of the first cen- tury, that the psalms in the Christian Church were rendered by a double chorus singing in alternation. It does not seem probable that these old psalms should have been sung to any other music than the old tunes. This music is scarcely more than emphatic declamation moving within the compass of a fifth ; only the cadences present a little more melodic variety. The use of instru- ments was strictly forbidden, because these played an important part in the religious cult of the pagans. This prejudice against instruments lasted for centuries. Plain chant, the only form of music ever oflicially sanctioned by the Church, never made use of instruments. Even the compli- cated polyphonic works of the school of the Netherlands and the great Roman school banish instrumental accompaniment. It is only with the rise of the school of Venice toward the end of the sixteenth century that instnunents find their way into the Church. When the plain chant melodies arose harmony was utterly un- known, and, consequently, the whole theory of music turned about melodic progression. Choral singing meant nothing else than singing in unison. As long as the persecutions compelled the early adherents of the faith to worship secretly in the catacombs, it was impossible to establish a uni- versal liturgj-. However, the melodies were pre- served among the various congregations and handed down from generation to generation by oral tradition, though we can scarcely doul)t that in the course of time the original melodies became more or less distorted. When, after the conver- sion of Constantine in .312, Christianity became the State religion, free intercourse between the difi"erent congregations became possible. Choirs were formed and received special training, so that congregational singing disappeared more and more. At the Council of Laodicea in 3(37 a decree was passed prohibiting any one but the regularly trained singers from singing in church. In the beginning of the fourth century Pope Sylvester established a singing-school at Rome, wliieh re- sulted toward the end of the same century in the composition of original hymns. Some of the old- est of these hynms are attributed to Saint Hilary, who was Bishop of Poitiers about 335. Saint Am- brose, Bishop of Milan, who died in 397, devoted all his energies to the arrangement and systema- tizing of all the then known plain chant melodies. To him is also ascribed the introduction of the
