ALTHOUGH the railway has scaled mountains, spanned gorges and canyons, crossed deserts, burrowed under streets and run for miles over open sea, Nature is always striving to impede its progress and break the iron links that girdle civilization. It was the work of heroes to construct the railways. The maintenance of them, and the continuous battle against the threat of sudden disaster, call for courage and determination almost equal to that which enabled the constructors of the great trans-continental systems to attain their goal.
Snow is the railway's most common enemy. In countries where falls are frequent—at one station in the Scandinavian peninsula it has been recorded that snow fell on sixty-two days of one year—it constitutes a perpetual menace. Despite the most strenuous efforts, it will often hold the railway in its grip for days, bringing traffic to a standstill.
The snow-shed offers an effective protection in mountainous districts where there are frequent avalanches, but on open stretches of the railway more drastic methods must be employed.
Snow-sheds built over the track are designed to provide paths over their roofs for avalanches. They are usually built of timber, although ferro-concrete is also used. The character of the snow-slide and its accustomed path has to be carefully studied so that the builder can modify the details of his design according to the speed, size and weight of the avalanche to be expected. In some places the length of travel is comparatively short, the bulk small, and for the most part comprised of snow only. In others the descent will be sharp and the speed great, with a large amount of timber, loose rock and other debris mixed with the mass of snow.
The contour of the ground on either side of the line has to be taken into consideration ; should the ground rise up again there is a possibility of the slide falling back on to the track on the far side after it has passed over the shed.
One form of avalanche defence provides a simple means of throwing the snow clear of the line. On the mountain side a wall of heavy rock is built to support massive baulks of timber which are so laid that they point upward over the track. The lower ends of these timbers are buried, and the ground is dug out to form a hollow. The descending snow, rushing into the depression and up the inclined plane provided by the timber baulks, flies off into the air clear of the track. The snow-shed forming a tunnel over the track is an expensive protection. The more elaborate types in concrete and masonry often cost £40,000 a mile.
A scudding, whirling snow-drift, driven by an icy blizzard, will fill a deep cutting, and on a flat, open stretch will pile up snow heaps which are not easily moved nor penetrated. Snow ploughs are used to deal with this menace. Although these machines have displaced vast armies of men, the human element cannot be dispensed with. Snow can still master the most ingenious mechanical device, and gangs of workmen are frequently summoned to dig out a plough after it has become caught in the grip of snow and ice, and can neither advance nor retreat.
The oldest and most common type of snow plough is in the form of a large wedge or double scoop, with a sharp prow, and is known as a wedge plough. This type is used only in those districts where the fall is relatively slight, and is not packed tightly.
It is operated by simple methods. The pointed nose of the plough is driven into the drift or bank, and the snow that is displaced by the prow is deflected along each side of the scoop and flung clear of the track. The snow, which may have banked high after drifting, does not always yield readily to the plough being pressed steadily forward. The machine then backs along the cleared track and makes repeated charges until the bank is overcome.
The wedge-plough is of little use in mountainous districts, where small boulders, bushes, broken saplings and other obstacles are often brought down with the snow. A rotary snow-plough is used to clear the track. This bores into the snow and, catching up the displaced material, whirls it clear of the track by the revolving action of a fan-shaped wheel. The knife edges cut the snow. which is dislodged and forced down the scoop until it reaches the rim of the wheel. Further progress is prevented by the drum, and the snow can escape only when the end of the scoop comes opposite a shoot in its hood. The centrifugal force set up is sufficient to enable the snow to be thrown in a continuous fountain high into the air, and extending as far as 60 ft. to the side of the track. The rotating wheel is driven by its own engine, and the plough is thrust forward by powerful locomotives.
Now and again obstructions will be met, and, unless the operators are fortunate, trouble follows. Sometimes a plough will be derailed, but it is usually the knives which suffer. There is a heavy sudden jolt, and if the obstruction is a boulder or a large tree-trunk, then the knives are torn off, or so damaged as to be useless. Demands, however, that the line shall be opened with all speed renders such accidents unavoidable, and unless the damage is extensive, the work of clearing the snow is continued.
With the big drifts and banks, where snow has frozen solid, "backing" is practised. The machine, with the locomotives, backs down the track, and then charges the obstruction in the same way that the wedge plough does its work.
The pressure is maintained until the machine drives its way through the packed mass, or is compelled to acknowledge defeat. In that event, there is no alternative but to revert to manual labour—to blast and shovel out the obstruction as if it were rock.
On steep mountain gradients the struggle between the railwaymen and the forces of nature is experienced to the full. Four or five powerful locomotives, the rims of their smoke-stacks only just visible above the level of the drift, are often required to break a way through.
Belching steam and smoke, and with the plough completely out of sight, though betrayed by the fountain of snow spouting high in the air, the great engines clear a deep, square-cut way through the white wall, just sufficiently wide to permit trains to pass.
On many modern railway systems much ot the work formerly undertaken by snow-ploughs has been eliminated by the construction of tunnels, which have also replaced many miles of track that were either entirely exposed to snowstorms or that were afforded only slight protection by snow-shedding. One ot the world's largest snow-sheds was built on the Central Pacific Company's line in America. This was over 29 miles in length and, known as "the house without end," it protected the railway against the severities of winter in certain parts of California.
A second and equally relentless enemy of the railway is the flood, the devastating effects of which are relatively little known in the British Isles ; but floods are only too familiar in other countries, such as India. Here the task of the railway engineers and bridge-builders in maintaining the track is stupendous. Many of the rivers—such as the Krishna, over two miles across in one place—are of imposing width and flow through low-lying territory. Flood water makes them susceptible to extreme fluctuations in level.
At some seasons the current whirls furiously along, and as the banks are mostly low and easily broken, the rivers frequently overflow, demolishing everything in their path. Should a railway embankment stand in their way, it is breached.
A river sometimes alters its whole course, and bridges are then left high over a dry river bed. During the flood season a river may overflow beyond its banks to the extent of three or four miles. When the water recedes to normal level it leaves behind long reaches of desolate sand.
To throw a bridge across such a river at a point where floods are prevalent is not only costly, but is also an enterprise which bristles with difficulties, owing to the instability of the constantly inundated low-lying ground. Although experience has proved that it is often futile to reclaim land wasted by water, engineers have discovered a highly effective means of fighting this enemy, and of reducing the lengths of bridges to reasonable proportions, thus saving the railway embankments from being "washed out."
The method of controlling rivers is effected by means of a "training bund"—a massive, solid embankment, erected parallel to the navigable channel, to direct the water in its flow. The tendency of the river is to drive a path behind this "bund," and this is checked by another similar embankment run out at right angles from the bank proper to the training bund itself.
These artificial works must be of immense strength to resist the enormous pressure and insidious scouring action of the swollen river. Large gaps are frequently made in the embankments by floods, with the result that the rails, with most of the sleepers still intact, are found draped across the breach like a graceful festoon. To restore traffic temporarily the engineers frequently have to erect trestle bridges.
Fire is the most terrible of all threats to the railway. Raging sometimes for days and nights in the dense forest regions, such as Canada and Western America, fire will reduce acres of growing timber to charred stumps and ash.
Where there is dry snow-shedding the danger to the railway is always present, for a spark from a passing locomotive or from a forest fire may set the structure blazing, and once the flames secure a firm hold nothing can save the shed or prevent the hold-up of traffic.
To reduce losses to a minimum snow-sheds are generally constructed in short sections, with long gaps in between, so that the possibility of the flames "jumping" is reduced.
Forest fires and avalanches would seem to have little in common, yet, since they weaken and kill the roots of trees, fires are frequently the forerunners of the dangers caused by avalanches.
To guard against the havoc of fire, water-pipes are carried through the sheds, and at close intervals lines of hose are provided ready for instant use. The sheds are patrolled day and night, so that any outbreak may be quelled in its early stages Telephone and wireless communication enables the squads of fire-rangers to summon assistance, and extra fire-fighting forces can be rushed up if the blaze gets beyond the power of the rangers on duty.
Where railway lines are laid through forest lands the track has to be constantly patrolled, and in the summer, when fires occur more often, the patrols are increased. To combat a large fire the lines of the section are taken over temporarily to convey the fire-fighters to the scene of action. The usual method of handling a bad outbreak is to clear a long. large area so that the flames have no chance to leap the gap and surge onwards to create fresh infernos.
Besides fire, flood and snow the railway has other enemies in tropical and semi-tropical regions such as earthquakes and volcanic eruptions. The effect of either of these is usually so disastrous that the railway in the vicinity is wrecked, and, when the lava stream has hardened, must be entirely reconstructed.
That man is slowly but surely winning this grim battle with Nature is proved by the fact that the railway still carries on. The fiercest forest fires and worst floods, although they may temporarily hold up the traffic, must not paralyse the vital arteries of international communication, and cannot defeat the ingenuity and courage of the railway engineer.