Natural bridge

“ The marvels of crystallization, the beautiful vegetable forms which the frost etches upon the stone flagging of the sidewalk, and upon the window-pane, delight us and we do not reason why. A natural bridge pleases more than one which is the work of an engineer, yet the natural bridge can only stand when it is based upon good engineering principles. ”

“ Natural bridges are short lived, geologically considered. The marble natural bridge in North Adams, Mass., for example, was formed many years after glacial times, but already a portion of the bridge has fallen in. ”

“ There are two other types of bridges which are entirely dissimilar. Tonto Natural Bridge, in central Arizona, is a “built-up” bridge created by travertine deposited by springs. Natural Bridge, in Virginia—another well-known bridge—apparently was formed when most of the roof of a cavern collapsed.
Wildlife
Deer are numerous in the pinyon and juniper forest which surrounds the monument, and mountain sheep, which spend their summers on the Elk Ridge, winter in the canyons. Smaller mammals are numerous, as are the coyotes and wildcats. An occasional lion works through the monument. ”

“ The dimensions of the bridges are:
How Natural Bridges Are Made
To make a natural bridge Mother Nature must have several ingredients: a proper stone that 3 will shape well (a cross-bedded sandstone is best) , a slowly rising landscape, and a desert-type stream that occasionally will scour its bed with a tremendous head of water and sand. All these were present in southern Utah.
The stone of the Natural Bridges area is a cross-bedded grey sandstone, known as the Cedar Mesa sandstone. ”

“ Further, as time goes on, and the progenitors of man become more human, the pressure of competitive life draws ever more and more attention to the incompleteness of natural bridges. For example, stepping-stones may be useless when they are needed most of all, in wet seasons and after storms; and the tree-bridge is so narrow that warriors cross it only one by one, so their slow attack gives a terrible advantage to a brave defence. These hindrances, so obvious and so unpleasant, make appeal to the inventive faculty that a few men possess. ”

“ A branch of the Southern Railway threads a natural tunnel near Anniston, Ala., and the tunnel is the remnant of an old limestone cavern.
In other cases a natural bridge is formed when bowlders,195 or a mass of rock, tumbling into a deep crevice is wedged and held in place. In still other instances a layer of hard or slowly weathering rock may rest upon a layer of rock which weathers rapidly. In such cases, if the rock layers form the face of a cliff, natural bridges, caverns, and overhangs are apt to result. ”

“ The ground rises from the edge of the deep water channel towards the shore with a gentle slope, the clay disappearing about half-way up, and giving place to ledges of freestone rock. It will thus be seen that the natural configuration of the ground on the centre line of the bridge, offers points or three main supports, of which the two outer ones are about equidistant from the central one, thus indicating two large spans of equal length, while the remaining spaces to be traversed on both shores, offer every facility for the construction of satisfactory foundations. ”

“ There are other references also, but the reader will be able to follow the history of piers from the natural bridge of stepping-stones through the many changes and defects mentioned in the text. To-day, with the rapid improvements in airships and aeroplanes, new armoured piers will have to be designed, strong enough to bear the great weight of a roofed superstructure of armour-plate steel, yet not thick enough to obstruct rivers. Now that bridges are as vulnerable as Zeppelin sheds, engineers have an excellent chance to serve their countries well by inventing new and powerful bridges. ”

“ There is always something picturesque and pleasant in an old bridge, and of historic associations as well. The great logs such as form a wooden bridge over a narrow stream are the most natural waterspans, those of the primitive savages. By fallen tree-trunks placed or utilized by the Indians, the colonists first crossed the inland streams, adding parallel trunks as years passed on and helping hands multiplied ”

“ It is a vast evolution from these natural things to the art of Ulric Grubenmann, the forerunner of metal suspension bridges. [52] Unfortunately it is also an evolution which we cannot follow through many consecutive phases, artists and historians having failed to record its growth. We cannot suppose that the [Pg 145] ancients neglected suspension bridges; from the spider alone they must have learnt that pendent ropes made a good bridge; but we know not what they achieved in this airy handicraft. ”

“ The rainbow bridge was the one great natural phenomenon, the one grand spectacle, which Shefford had ever seen that did not at first give vague disappointment, a confounding of reality, a disenchantment of contrast with what the mind had conceived. ”

“ He crawls along fallen trees over some torrents and chasms; across a flooded river here and there he leaps in a shambling, lopsided fashion, when stepping-stones and boulders rise above water-level; he roams into hilly districts where many a ledge of rock spans a dangerous gap; but he enjoys himself most of all when a suspension bridge of branches enables him to amble from tree to tree across a deep-lying river pent up between high cliffs. ”

“ Great marble bridges of a single span stretch from mountain to mountain over deep chasms. Nothing can be more imposing than the construction and the situation of those bridges, cast into space as it were, and swimming in the white, moist atmosphere which seems to fall regretfully into the ravine. The road passes from one side of the gorge to the other seven times in the space of four leagues. When our travellers crossed the seventh bridge, they saw at the bottom of the gorge, which widened almost imperceptibly before them, the charming valley of Luz, bathed in the flames of the rising sun. ”

“ The two approach roads serving Natural Bridges National Monument from Blanding, Utah, are unsurfaced dirt roads with steep grades. During heavy rain storms they become either difficult or impassable to travel. ”

“ It is in the middle of the river, on a huge slippery rock, amidst other innumerable fragments, over and against which the impatient water loudly dashes; having huge towering rocks, full of clifted chasms, over-run with wood on each side; and in front, the small arch of the bridge just visible, through the thick shade of wood and rock, at least one hundred feet above the eye. In such a situation it is almost impossible to preserve one's head from swimming. ”

“ Only rarely does one see the hut of rough logs and clay that denotes the settler, only occasionally is there a station, or a mill or a logging camp in this womb of loneliness. Only occasionally does one cross one of those lengthy and rakish spider bridges that give a hint of man and his works.
On a long bridge, over the Montreal river, we made the most of man and his works. It is a lengthy, curving bridge, built giddily on stilts above the boulder-strewn bed of a wicked stream. We were admiring it as a desperate work of engineering, when the train stopped with a disconcerting bump. ”

“ The most usual form has its counterpart in those rocky arches which flood and fire have excavated or penned up in many picturesque regions,—the segments of caverns, or the ribs of strata,—so that, without the instinctive suggestion of the mind itself, Nature furnishes complete models of a bridge whereon neither Art nor Science can improve. Herein the most advanced and the most rude peoples own a common skill; bridges, of some kind, and all adapted to their respective countries, being the familiar invention of savage necessity and architectural genius. ”

“ We wound up the narrow valley in splendid loops and curves, turning upon our tracks, running through numerous tunnels, and at one time crossing a chasm so narrow and with sides so steep and precipitous that it was found necessary to build the bridge in two parts, each against the face of the cliff, and then gradually lower them until they met above the river, three hundred and fifty feet below. ”

“ If you have been there, you remember that if you turn to the right and go over the stone bridge that crosses the sleepy river, you are in the very heart of beauty. You pick your way daintily along the edge of the road, for it is carpeted so thickly with sea-pinks and yellow and crimson crow’s-foot that you scarcely know where to step. Sea-poppies there are, too, groves of them, growing in the sandy stretches that lie close to and border the wide, shingly beach. In summer the long, low, narrow stone bridge crosses no water, but just here is an acre or two of tall green rushes. ”

“ In these four bridges, each of them generic, Nature has arrived at utility in her usual manner, by alternating growth and violence. The fallen tree, for instance, from which all timber bridges have been evolved by handicraft in a sequence of gradual improvements, belongs to the utility of Nature’s violent moods; and this applies also to the bridge of stepping-stones. Earthquakes and floods distributed boulders over the beds of rivers, and from these boulders handicraft has developed piers and abutments. ”

“ There are trees that grow to an enormous height; one of them measured a hundred feet odd, so fairly wide creeks and streams can be bridged. But canoes are the favourite means of crossing rivers; they carry light loads well enough, and they need less labour than bridge-building.”
This peep into the aboriginal mind reveals a dire stagnation. But although no other thing in Nature is less uncommon than human initiative, yet the men of the eagle-beaked tools may have made tree-bridges, and also such stone bridges as the lintel-slabs at Wycollar (p. 60) . ”

“ You are standing aloft, balancing yourself upon tiny planks at the steadily advancing end of the bridge, as it forces itself over a stream of formidable width. Overhead, a gigantic, ungainly traveller, equipped with steel derricks at every corner, is advancing foot by foot as the bridge advances foot by foot. Underneath, through the thin network of planks, of girder and of supporting false work, you can see the surface of the river a full hundred feet below. ”

“ These were approaches to the big covered bridge spanning the main channel of the Madawaska River, and when swelled by the spring thaws and rains, the two flanking channels divided at the foundations of the house, and rustled away through the narrow paths of the small bridges to the rapids. You could stand at any window in the House and watch the ugly, rushing current, gorged with logs, come battering at the wall, jostle between the piers, and race on to the rocks and the dam and the slide beyond. ”

“ At times they settle under a rock-shelter or in a cave, and make footpaths from it to watering-places and hunting-grounds. Here and there a river is crossed by stepping-stones, and more than one ravine is spanned by branches and by a fallen tree. What is their attitude to these things? The windfall tree-bridge, like every other gift from Nature, is a [Pg 119] bane to them as well as a boon, for it is a road open to dangerous animals; as such it is a thing to be guarded, and many a fight in its defence occurs, creating traditions of bravery which are long remembered. ”

“ Once across, the traveller might find his path or make it for himself. Parapets are not provided on the old bridges, and the surface is a flight of broad and shallow steps. If you walk unwarily and are drowned in the torrent below, that is no concern of these resolute but unluxurious bridge-builders. Their business is simply to span the stream. ”

“ Entering a tunnel in the vast wall of rock the train emerges again at one end of the bridge, and after crossing the gulf turns along the other side so that for some long time this narrowest part remains in sight, the maroon red ironwork of the bridge staring dramatically in the centre of a desolate landscape of silver grey. No patch of grass or shrub or any other live thing is to be seen—only the immensity of the scale is marked {289} by one small block-house, a minute sentinel which shows against the sky on the tallest height of cliff. ”

“ But in winter Nature breathes upon his handiwork and transforms it. Bridges may be imposing and of great artificial beauty in cities—as for instance the ancient structure that spans the Tiber just below the tomb of Hadrian, or among modern works the spider web engineering feat of Brooklyn bridge—but if in the wilderness we run across them, there is something incongruous about them, and they disturb. Strange to say, there is the exception of high-flung trellis-viaducts bridging the chasm of mountain canyons. ”

“ Sometimes a hanging bridge has to be crossed, spanning a horrid chasm, at the bottom of which roars a foaming torrent—the bridge itself, composed of ropes and brambles, all the while swinging like a hammock under the tread of the affrighted traveller! ”

“ It would be easy in a shallow river to make a fish-pool by heaping boulders into a dam of this rude sort, and the completed work would rank no higher than the beavers contests against running water. So I tell myself that many a tribe in the great period of prehistoric art, about 50,000 years B.C., ought to have built for itself a bridge as elementary as the Pont-y-Pant and a perforated dam as uncouth as the one at Thirlmere. ”

“ Beyond the towers workmen in great numbers deepened a fosse, heaped ramparts, strengthened walls, and in the earth over which Montmaure must advance planted sharpened stakes and all gins and snares that the inventive mind might devise. To hold this bridge was of an importance!—South and east stretched the yet unharried lands and the roads by which must come in food for the town, the roads by which it might keep in touch with the world without, the roads by which might travel succour! ”