Dam

“ With a loud roar the waters rush forward, sweeping the rocks and stones of the dam along in their resistless strength, and with a noise as of thunder, above which the despairing shrieks of the myalls rise for one brief second, the hapless wretches are torn from their feeble hold of the rock and, swept into the awful rush and crash of the cascade, are flung with the rolling stones of the broken dam, and battered into silence and death upon the frightful rocks below. ”

“ When the dam is built, and the water deep enough for safety, the beavers dig a canal around one end of the dam to carry off the surplus water. I know of nothing in all the woods and fields that brings one closer in thought and sympathy to the little wild folk than to come across one of these canals, the water pouring safely through it past the beaver's handiwork, the dam stretching straight and solid across the stream, and the domed houses rising beyond. ”

“ By night and by day the river leans heavily against the dam. Tiny, sharp currents, like fingers, tear constantly at the structure, working always underneath. Hidden and undreamed-of eddies burrow beneath the dam; little river animals undermine it, ever so slightly, with tooth and claw.
At last an imperceptible opening is made. Streams rush down from the mountain to join the river; even raindrops lend their individually insignificant aid. All the forces of nature are subtly arrayed against the obstruction in the river channel. ”

“ At time of flood young tributaries with steeper courses than that of the trunk stream may bring down stones and finer waste, which the gentler current cannot move along, and throw them as a dam across its way. ”

“ When we stop for a few minutes, in order that I may gather wild flowers, the silence is very striking, only the distant treble of the bleating lamb far up the mountain side, and the answering cry of the dam. ”

“ The sun being now low towards the west, a pleasant gloom and brightness were diffused through the forest, spots of brightness scattered upon the branches, or thrown down in gold upon the last year's leaves among the trees. At last we came to where a dam had been built across the brook many years ago, and was now gone to ruin, so as to make the spot look more solitary and wilder than if man had never left vestiges of his toil there. ”

“ It is a most interesting sight when it comes at last, and well repays the watching. The water is pouring through a five-foot break in the dam; the roof of a house is in ruins. You have rubbed yourself all over with fir boughs, to destroy some of the scent in your clothes, and hidden yourself in the top of a fallen tree. ”

“ How early we are all astir on the morning after a big rain! and with what eager excitement we look out, in the first gleam of daylight, for that most welcome sight, the newly-filled dam! A wonderful transformation has indeed been worked in the appearance of things since last night. That unsightly dry bed of light-coloured soil, baked by the hot sun to the hardness of pottery, and broken up by a thousand intersecting deep cracks and fissures, which has so long been the ugliest feature among all our unpicturesque surroundings, offends the eye no more ”

“ Just as the higher and stronger the dam is built to stem the current of the rapid and deep waters of the river, the more awful the disasters which follow its destruction, so it is with that noble soul. ”

“ Think of the huge bulk of water held up when the reservoir is full. Then you will understand something of the difficulties of the work. Solidity and strength could not but be the first and overpowering idea in the minds of the builders. The longer you look, the more you are impressed. The vast dimensions of the Dam grow upon you from moment to moment. There is, after all, a fierce beauty in those uncompromising features, grimly set in the determination to hold the river in bondage. The massive structure is in harmony with the forces of Nature. ”

“ A short distance above the hill upon which it is built, the water of the river that glides along its base may be seen springing over the low dam that obstructs its passage, sparkling, glistening, dancing in the sunlight, as it falls splashing on the stones below ”

“ In some former time an old mill had stood at the foot of the little valley, and a ruinous stone dam still held the water in a deep, quiet pond between two round hills. Above it a brook ran down through the woods, and below, with a pleasant musical sound, the water dripped over the mossy stone lips of the dam and fell into the rocky pool below. Nature had long ago healed the wounds of men ”

“ This circumstance, in connexion with the stream that washes its outer base, has caused large and over hanging projections of the stalactical deposites, and cavernous excavations; attached to the roofs of which is to be seen a great variety of small and beautiful spars. At the point over which the water at present is precipitated, the dam, is a bold and interesting spectacle. Add to this a large descending column of white spray, into which the water is converted by obstacles opposing its march over the dam, and the scene is rendered truly sublime. ”

“ A few oar-strokes distant lies a dam or water-break, where the whole lake is held under control by certain distant mills, towards which a sluggish stream goes winding on through miles of water-lilies. The old gray timbers of the dam are the natural resort of every boy or boatman within their reach; some come in pursuit of pickerel, some of turtles, some of bull-frogs, some of lilies, some of bathing. ”

“ Out in the center of the lake bed a swiftly diminishing flow of water was vanishing toward the dam. In five minutes at most nothing would be left save the narrow, crooked stream curving between slopes of mud. ”

“ Then they all looked around again, their eyes naturally roving in the quarter where, near the farther end of the dam, the old mill stood.
Its day was long since past. The great water wheel at the end of the sluice had partly fallen to pieces with the passage of time and the ravages of neglect. What was left seemed to be almost entirely covered with green moss, among which the clear little fingers of water trickled. ”

“ A good-sized dam is sometimes half a mile broad, and, when just filled after a good thunder-shower, is quite an imposing sheet of water. Occasionally, in very heavy thunder-storms, the glorious supplies pour in too lavishly; the embankment, unable to resist the pressure, gives way; and the disappointed farmer, who has ridden up in the hope of feasting his eyes on watery wealth, beholds his treasure flowing uselessly and aimlessly away across the veldt. ”

“ The runnel which feeds it descends from the snow-capped peak to the south, and copious supplies trickle through the soppy margin at the base of the dripping hills around. The surplus escapes through a head to the north, where a gated dam is thrown across to raise the level, and to regulate the water-power. ”

“ They also fill up all the gaps between them with mud, and so hard do they work that by the time the dam is finished it is often two hundred yards long, fifteen or even twenty feet thick at the bottom, and six or eight feet high. And when the river runs swiftly, they are clever enough to make their dam in the form of a curve, so that it may be better able to resist the force of the current. ”

“ Below the dam, where the valley is rather broader and the ground naturally low and marshy, a second, lower and smaller lake has been formed, the dam of which, of a slight character, may be seen along the upper side of the road from the station to the castle. This lower lake must always have been shallow, but it served to protect the great dam, to cover the south-east angle of the castle, and to guard the rear and eastern flank of the great outwork. ”

“ The bottom of the river is loose and unstable; and the shores are so friable, that if an attempt is made to build a dam across it at once, the water will, in the mean time, be working out for itself new channels along the sides. ”

“ The dam is a loosely constructed barrier, seldom in water over three feet deep, and generally rising but little above the surface. As the parts of trees of which it is built are of kinds which easily take root from rods or wands, as willow, birch, and alder, these sometimes shoot up and spread, growing into a kind of hedge, which, catching débris coming down stream, constantly increases the strength and size of the structure. Slight and low as the beaver dam is, it is marvellous that a brute should construct it, and its size is by no means contemptible. ”

“ If unmolested, the old dam is chosen; but if the hated man-smell is there, new waterways are sought. Burrows and washes and channels and retreats are cleaned out. Trees are cut and a great supply of branches laid up for winter store near the lodge, not a chip of edible bark being wasted. Just before the frost they begin building or repairing the dam. Each night's frost hardens the plastered clay till the conical wattled roof—never more than two feet thick—will support the weight of a moose. ”

“ Rows of willows or mimosas are generally planted along the banks of the dams; and though the moisture which is sucked up by their thirsty roots can ill be afforded, yet, in that most treeless of lands, their bright, fresh green is of immense value; and the poor ugly houses, standing so forlornly on the bare veldt, with but the narrowest and scantiest of gardens—if any—between them and the surrounding desert, seem redeemed from utter dreariness and desolation, and some slight look of home and of refinement is imparted by the dam's semicircle of trees. ”

“ This, as Jack further whispered, was to break the force of the current and shunt it off gradually to each side of the dam.
It was the same principle that in a racing [94] automobile gives the cigar-like point to the machine so as to act as a wedge going into the wind and lessening by that much its resistance. The base of the dam was formed by young saplings and branches of trees that had been cut by the beavers’ teeth and planted as piles. ”

“ The dam is an indispensable institution in a country where springs are scarce, and where a river is a prodigy. It is the new settler’s first work, even before erecting his house, to find a hollow space, and dam it up, so as to make a reservoir. ”

“ This extra flow disturbed both the colour and the temperature of the clear amber water of the pond. It lifted heavily against the ice, pressed up the tunnels to the very edge of the dry chamber of the lodge, and thrust ponderously at the outlets of the dam. Understanding the peril, the wise little dam-builders sallied forth in a flurry, and with [Pg 249] skilful tooth and claw lost no time in enlarging the outlets. They were much too intelligent to let the flood escape by a single outlet, lest the concentrated flow should become too heavy for them to control it. ”

“ The effective head at any point of an earth dam has been defined as the difference in the elevation of the high-water surface in the reservoir and that of the intersection of the down-stream slope with the natural or restored surface of the ground below the dam. ”

“ Then we clinked over sulphur in crystals; there was a waterfall of boiling water; and a road across a level park hotly contested by the beavers. Every winter they build their dam and flood the low-lying land; every summer that dam [Pg 099] is torn up by the Government, and for half a mile you must plough axle-deep in water, the willows brushing into the buggy, and little waterways branching off right and left. The road is the main stream—just like the Bolan line in flood. If you turn up a byway, there is no more of you, and the beavers work your buggy into next year's dam. ”

“ Where the flow of water is but small, the dam is constructed in a straight line across it; where it is liable to be swollen greatly by rain, it is built in a concave form, so as to break the force of the current. ”

“ Both the original dam and the reconstructed one were built of earth only, with no heart wall and rip-rapped only, on the slopes. True, the earth is of a sticky, clayey quality; the best of earth for adhesiveness, and the old dam was made in watered layers, well rammed down, as is still shown in the wrecked dam. ”

“ Dam Site.
The third preliminary study (that relating to the dam site itself) will be considered under three heads:
1. Location.
2. Physical features, materials, etc.
3. Foundation.
LOCATION.–The location for a dam is generally determined by the use which is to be made of it, or by the natural advantages for storage which it may possess. If it be for water power it is very frequently located upon the main stream at the point of greatest declivity. If for storage it may be, as we have seen, at the head of a river system, on one of its tributaries, or in a valley lower down. ”

“ Putting aside the natural dams made by accumulations of the various debris that are washed down by a swollen stream, and which sometimes raise the water to a very great height, we have an example of a natural dam in the curious structure made by the Beaver, for the same purpose as that of the lock in the mill-stream, namely, to insure a depth of water sufficient for the needs of the beings that make them. ”

“ The circumstances that the dam is only constructed at the lower end of the watercourse, and that it is there that the fish are to be met with in the greatest numbers, seem to indicate that they can travel in the ooze, and that as the brooks and ditches get dried up, they seek the larger water channels. ”