Mountain, a considerable elevation of the earth's surface, either isolated or arranged in a linear manner. Great regions of the earth are much elevated above the sea, forming high plains, called table lands or plateaus, from which mountains often rise. Such are the great plain of Thibet, with an average height of 16,000 ft.; that of western Asia, from 4,000 .......; and that of western North America, of about the same height, from which rise the Rocky mountains and the Sierra Nevada. The elevation of mountains is generally calculated from the sea level. With few exceptions the mountains of the earth are arranged in continuous lines or chains, and a mountain system consists of parallel chains with intervening val-leys. The great mountain system of the Ame-rican continent is that which has been called the Pacific highlands, extending from Alaska to Cape Horn along the W. part of the continent. It consists in the United States, exclusive of Alaska, of the Rocky mountains to the east and the Sierra Nevada and Cascade mountains to the west, rising from the broad table land already mentioned, and having between them the great central basin with its subordinate mountain ranges. The highest points in both of these chains attain about 15,000 ft.
The highest mountains in Alaska (Mt. St. Elias) and Mexico (Popocatepetl and Orizaba) rise to a height of nearly 18,000 ft. In South America the same great continental system consists of two, and in some parts of its course of three chains, separated by narrow elevated valleys. The general breadth of the whole system of the And. is between 100 and 300 m., and the greatest height is attained in the plateau of Bolivia and in Chili, where there are peaks of from 20,000 to 23,000 or. according to some, 25,000 ft. In eastern North America are the Atlantic highlands or Appalachians, extending from the gulf of St. Lawrence to Alabama'; these attain their greatest elevation in the Black mountains of western North Carolina, where there are several peaks of over 6,000 ft., one reaching 6,700 ft., and in New Hampshire, where the highest, Mt. Washington, is 6,285 ft. In the intermediate portions the heights are less, and in New York the tidal valley of the Hudson traverses the range. To the north and west of the Hudson are the Adirondack, Helderberg, and Catskill mountains, which in their continuation southward form the Alleghany and Cumberland mountains.
Between this belt and the eastern one, which, extending from the Green mountains ami White mountains of New England, and the Highlands of the Hudson, takes the name of the Blue Ridge S. of the Potomac, lies what is called the great Appalachian valley, which itself attains a considerable elevation in S. W. Virginia. - From the plateau of Brazil rises along its E. portion a chain corresponding to the Appalachian; and in Africa there are similar highlands on the two sides of the continent, those of the eastern attaining an elevation of 20,000 ft. A like arrangement of highlands is seen in Australia, where however the highest elevation is about 7,000 ft. In Europe the Scandinavian and the Ural mountains are N. and S. chains, like the Appalachians; but the great mountain systems of the eastern hemisphere have a general E. and W. direction from the Atlantic to the Pacific. The Pyrenees, the Alps, the Balkan, the Caucasus, the Himalaya, and various subordinate ranges, mark this great mountain belt. Of these the Pyrenees have a crest line of about 8,000 ft., but attain in some peaks 11,000; the Alps have an average height of from 10,000 to 12,000 ft., the highest peak being Mont Blanc, 15,732 (or 15,781) ft., while the Himalayas rise in many points to 25,000 ft., and attain in Mt. Everest 29,000 ft., and the Thian-shan range, N. of these, is from 15,000 to 20,000 ft.
The chains of this great mountain region of the eastern hemisphere are not always parallel, but are often considerably divergent. - The slopes of mountains are generally very gradual. Thus the average ascent of the Andes from the E. side is about 60 ft. in a mile, and on the bolder W. slope from 100 to 150 ft. in a mile; while for the E. slope of the Rocky mountains the average ascent to the great plateau is not more than 10 ft. in a mile. A much more rapid inclination than any of these is seen for isolated peaks, of which a very remarkable sample is Mont Blanc, which rises from the valleys on either side at an inclination of about 30°. The slope of the volcanic cone of Jorullo in Mexico is about the same, while those of Mt. Etna and Mauna Loa in the Hawaiian islands (reckoning from the base) are not more than 5° or 6°. The relations of mountains to climate are very important, but the discussion of them belongs to meteorology. - The early history of mountains, or orography, as it is called, presents crude notions. By the older geologists mountains were supposed to be thrust up by some force from within, and were compared to bubbles on the earth's crust.
Some geologists of the present century have maintained this notion, and have even speculated upon the cataclysmal effects of a sudden upheaval of a mountain chain like the Pyrenees from beneath the ocean. But these conceptions have given place to more rational ideas. We must distinguish two classes of mountains, of widely different origin: those which are produced by the accumulation of matters ejected from volcanic vents, and those which have been formed by erosion. The first class, of which Etna and Vesuvius may bo taken as types, have been built up as an ant hill is raised by matters brought grain by grain from below the surface. Successive overflows of molten rock or lava, and showers of dust and scoriae, the solidified scum of the lava, have heaped up these volcanic cones; while from time to time fissures or ruptures in the mass have allowed the injection of dikes of molten matter, which in cooling have given solidity to the whole. Volcanic cones are in fact generated in the air by the force of gravity.
Volcanic vents may occur alike beneath the sea, in low plains, or on elevated plateaus, and sometimes from the summits of mountains not themselves volcanic. (See Volcano.) But the mountains of purely volcanic origin are insignificant when compared with the great systems of mountains which are not volcanic, or in which the presence of volcanic vents is but a secondary fact. These mountains, whether composed of aqueous or of igneous rocks, have had a very different origin from volcanic cones. They are due to erosion, and are the remains of great plateaus, the larger part of which has been removed. They are but fragments of the upper crust of the earth, separated from each other by valleys which represent the absence or the removal of mountain land. The popular conception is that mountain chains are due to the folding and plication of strata; but careful study of their structure shows that these are but accidents of structure, in no way essential to the formation of mountains, and sometimes absent. To De Montlosier and to J. P. Lesley we owe our first conceptions of the true nature and origin of mountains and valleys, and to James Hall its further elucidation and its illustration by the facts of North American geology.
That the crust of the earth is not rigid, but yielding, and subject to movements of depression and elevation, due to a disturbance of its equilibrium, which have in all ages been operating, is evident from the distribution of sedimentary deposits in past geological periods. In addition to these there are other movements which are conceived to be due to the contraction of the earth's nucleus, resulting also in movements of depression and elevation of the surface, and in corrugations of portions of the crust. The result of these is seen in undulations of the stratified rocks, which are sometimes very slight and regular, but at other times both marked and irregular, occasionally giving rise to great overturns, folds, or inversions, and sometimes enclosing a portion of the rocks in a great fold until there is an inversion of the pinched-up strata on both sides of the axis of the fold, by which they come to present a far-like structure when seen in transverse section. In other cases occur breaks or slidings of the strata on one another, and frequently more or less nearly vertical displacements, or faults, as they are called, by which the strata on one side of a line of fracture may be raised several thousand feet above the same strata on the other side.
These various disturbances of the strata influence in many ways the eroding agencies of the elements, so that the mountain outlines and the distribution of mountains and valleys depend upon these accidents, though not the elevation of the mountain plateau. Thus the crest of a fold from which the strata dip in opposite directions, making what is called in stratigraphy an anticlinal axis, will generally be fractured by the strain which this part has suffered, and will then present a line of weakness which becomes a line of erosion. Valleys are thus cut out, and the strata between the adjacent anticlinals, escaping the eroding action, form a synclinal mountain range, the beds in their natural order dipping from the valleys on each side toward the centre of the mountain. Such a condition of things is seen in the anthracite region of Pennsylvania, in the Catskill mountains of New York, and in western Vermont. From irregularities in the undulations, from faults, or from the intervention of harder and softer beds, it often happens that the process of erosion is less regular than this.
Sometimes an anticlinal mountain appears; at other times an anticlinal mountain is divided, presenting two monoclinal mountains, or, as the result of a great fault in the strata, a single mountain of this kind in which the strata dip to one side. For a further discussion of the various forms of mountain structure, see Lesley's "Manual of Coal and its Topography." - The structure of mountains is best studied in regions of un-crystalline rocks, where the strata have not been too much disturbed, and where stratification is very evident, as in the palaeozoic rocks of the Appalachians. In the crystalline eozoic rocks of this mountain system, where the strata are greatly disturbed and nearly vertical, the study of mountain structure is much more difficult. Mountains do not owe their elevation to any folding, or crushing, or piling up of the strata. The influence of folding has been well pointed out by Hall, who has shown the relations of the elevations of palaeozoic rocks in the United States to the accumulation of sediments.
In the upper part of the Mississippi valley, where the palaeozoic rocks are represented by 3,000 or 4,000 ft. of sediments, we find hills made up of horizontal strata, the lower Cambrian rocks which form the base of the hills being everywhere above the water level, while the height of the hills is equal to the vertical thickness of the strata which compose them. In Pennsylvania, on the contrary, where the palaeozoic strata have a vertical thickness of about 40,000 ft., the synclinal mountains, having in their summits the upper beds of the series, are not more than 2,000 or 3,000 ft. high, the greater part of the strata having been removed from the anticlinal valleys while they are sunk far beneath the mountains. It follows from what has been said that in horizontal and synclinal mountains the newer rocks are at the top and the older ones at the base, but in overturned and dislocated strata this is of course no longer the case. In regions where, as the result of great folds and overturns, the fan-like structure already described has been produced, the older rocks from beneath are made to surmount and rest upon the newer strata, which have folded and doubled up beneath them.
The erosion of such a region gives rise to a mountain like Mont Blanc; in this the ancient crystalline strata, which elsewhere form the floor upon which repose the newer stratified rocks, rise above these, forming the summit of the mountain, while at lower levels on its flanks the newer strata seem to dip toward the centre of the mountain, but are really bent upon themselves and doubled up. as is seen in the valley of Chamouni. Mont Blanc, which served as a type to the early students of geology, is thus an exception. The crystalline strata which form its summit were looked upon as an upthrust of granite which had lifted upon its sides the newer stratified rocks, thus giving the mountain, as was imagined, an anticlinal structure. In the process of sculpturing the earth's surface by ocean current, frost, rain, and rivers, the unequal erosion exposes the harder masses, and thus eruptive rocks lying in the midst of softer strata appear in the form of hills, as is seen in the trappean ranges of New Jersey and the Connecticut valley. Isolated peaks of a similar origin are found in the vicinity of Montreal, and are denuded masses of eruptive rock which were once included in the soft palaeozoic strata of the region long since removed by erosion.
They were perhaps the stocks or underground portions of volcanoes in palaeozoic times. - The question of the geological age of mountain- is twofold, including, first, that of the deposition of the rocks of which they are composed, and second, that of their uplifting and erosion. Elie de Beaumont, considering only the latter question, supposed all mountain chains having the same direction on the earth's surface to be of the same age; but this notion is no longer tenable, since a great mountain chain, such as the Appalachians, exhibits considerable variations in different parts of its course, from a X. and S. direction in parts of New England to one nearly E. and W. in other parts of its extension. As regards the age of the rock, of this great chain, while the Green and white mountains, the Adirondacks, and the Blue Ridge are eozoic, the Catskills, the Alle-ghanies,the Unaka, and the Cumberland ranges are composed of palaeozoic sediments, and the whole Appalachian system was not uplifted until after the deposition of the coal.
The study of the Alps shows that the elevation of this great mountain system was still later, since even tertiary rocks are involved in the' folds and inversions of the strata.
Jacob, a Canadian bishop, born in Norfolk, England, in 1750, died in Quebec June. 16, 1825. His grandfather, Jacob de Montaigne, a great-grandson of Montaigne the essayist, was banished from France by the revocation of the edict of Nantes. He graduated at Oaius college, Cambridge, in 1774, became a fellow in 1777, and in 1781 was nominated to the living of St. Andrew's, Norwich, holding besides several other livings. In 1793 he was appointed first Protestant bishop of Quebec. He found but nine clergymen in his diocese, and labored for 30 years to build churches and schools and to promote the spiritual welfare of his flock.
George Jehoshapliat, second son of the preceding, born in Norwich, July 27, 1780, died in Quebec, Jan. 8, 1863. He graduated at Trinity college, Cambridge, in 1810, was ordained priest in 1813, and appointed evening lecturer in his father's cathedral. In 1814 he was nominated rector of Fredericton, New Brunswick, and in 1817 rector of Quebec and bishop's official. In 1821 he became archdeacon, and in 1825, during a mission to England, he received the degree of D. D. On his return Bishop Stuvard appointed him his examining chaplain, and in 1835 he was sent to England on business connected with the question of the clergy reserves. While there he was appointed bishop of Montreal, and given the entire charge of the Episcopal church in Lower Canada. He continued to administer the dioceses of Quebec and Montreal till 1850, when he assumed the title of bishop of Quebec. In 1844 he visited the missions on Red river, composing during his journeys "Songs of the Wilderness" (London, 1846). He was the founder of Bishop's college, Lennoxville, and of the church society, spending most of his income for these institutions and for charitable purposes.
Some time before his death he declined the dignity of metropolitan of Canada. He published sermons and addresses, and a "Journal of a Northwest American Mission" (London, 1843).