As the ages passed, those life forms were buried by mud and silt brought down from surrounding mountains by the raging rivers of those days.
The weight of the silt caused it to turn into sandstone or limestone layers hundreds of feet thick.
At the Kidderpur docks on the Hugli, the water from the river for replenishing the docks is conducted by a circuitous canal, in which it deposits its burden of silt before it is pumped into the docks.
Before driving the piles, however, the silt round the upper part of the piles and under the quay wall was consolidated by depositing small stones in a trench dredged to a depth of 30 ft.
The entrance to this snug little port is about forty yards in width, and the depth is most irregular, varying from dry silt close to the south end of the reefs up to twelve feet beneath the walls of the fortress.
The stream is gray with silt and loaded with sand and gravel washed from the ground moraine.
Red residual clays accumulated on the mountain sides and upland summits, and were washed as ocherous silt to mingle with the delta sands.
The silt brought down in suspension in a year would cover a square mile to the depth of four feet.
Yellow and red muds occur where the amount of iron oxide in the silt brought down to the sea by rivers is too great to be reduced, or decomposed, by the organic matter present.
Few forms of life can live in bodies of salt water so concentrated that chemical deposits take place, and hence the beds of salt, gypsum, and silt of such lakes are quite barren of the remains of life.
This consists of the silt which the stream carries in suspension, and the sand and gravel and larger stones which it pushes along its bed.
The amount of silt to a cubic foot of water is found by filtering samples of the water taken from different parts of the stream and at different times in the year, and drying and weighing the residues.
The average amount of silt to the cubic foot of water, multiplied by the number of cubic feet of water discharged per year, gives the total load carried in suspension during that time.
Off the mouths of rivers, stratification is also caused by the coarser and more abundant material brought down at time of floods being laid on the finer silt which is discharged during ordinary stages.
Muds are also found near shore, carpeting the floors of estuaries, and among stretches of sandy deposits in hollows where the more quiet water has permitted the finer silt to rest.
WELL WITH SILT BASIN, OR TRAP, AND COVER.
If silt or earth has caused the obstruction, it is probably because of a depression in the line of the drain, or a defect in some junction with other drains, and this may require the taking up of more or less of the pipes.
If the soil be clay, we do not believe it is best to return it directly upon the tiles, because it is liable to puddle and stop the joint, and then to crack and admit silt at the joint, while gravel is not thus affected.
Where extensive drainage is carried on in low-lying districts, and the principal outlet at a considerable distance, it may be found necessary to have traps at several points where the silt from the tiles will be kept.
These wells, sometimes calledsilt basins, or traps, are frequently used in road drainage, or in sewers where large deposits are made by the drainage water.
He cleared the silt out of the Siloam tunnel so as to reveal its real depth, which seems to have been between five and six feet.
The great alluvial plain lies north of the river; the three streams whose silt contributes to form it flow into the main channel from Pistoja and Prato.
It was the place that yet bears the name of Minster, situated on a little creek of the Wantsum sea, where some slight remains of an ancient pier may even now be traced among the silt of the marshes.
The colossal accumulation of silt thus produced filled up at last all the great arm of the sea between the two mountain chains, and joined the Deccan by slow degrees to the continent of Asia.
The bricks of Babylon were moulded of Euphrates mud; the greatness of Nineveh reposed on the silt of the Tigris.
Shrubs as far as 5000 feet away from ground zero were damaged by air blast, and, in the weeks after the detonation, plants within a two-mile radius were covered by radioactive sand and silt or by deposits of windblown radioactive dust.
The test islands still bore nuclear scars, and in some areas of the lagoon corals and algae had been killed by silt stirred up by the detonations.
If the drain is on a true grade, so that no silt will collect, there need be no fear concerning its continued efficiency, provided water does not run in it all the time.
This grade insures against deposits of silt and gives good capacity to the drains.
The incorporation of organic matter with clay or silt changes the character of such land, breaking up the mass, and giving it the porous condition so essential to productiveness.
In times of heavy rainfall water may back up into the main with no injury other than temporary failure to perform its work, but continuous submersion will lead to deposits of silt that may close the tile.
At any instant firm rock may cease, silt or sand or an underground stream may make its appearance and the helpless workmen find a ready grave.
In the silt the most satisfactory and economic progress was attained, and a record was made of seventy-two feet of finished tunnel, completely lined with iron, in one day of twenty-four hours.
The most difficult combination that had to be dealt with under the river was when the bottom consisted of rock and the top of silt and wet sand.
Underneath the silt of the river, then, and the sand of the desert, lie these two formations of the Tertiary division.
Beneath this lay the peaty substance of the lake-bottom, through which an iron rod could be readily plunged to the extent of 4 feet, when it struck some hard material, probably rock orsilt of the original glacial bottom.
Thus, the increase of silt since the terramara settlement of Casale Zaffanella was founded, amounts to 12½ feet--a depth sufficient to cover the highest part of the mound.
East of Devil's Point, the Saskatchewan breaks from its river bed and is lost for a hundred and fifty miles through a country of pure muskeg, quaking silt soft as sponge, overgrown with reed and goose grass.
It was a new river, with wonderful purple water--the purple of river silt blending with ocean blue.
The river swept down behind a deep harbour, with forested heights between river-mouth and roadstead, as if nature had purposely interposed to guard this harbour against the deposit of silt borne down by the mighty stream.
If then the stream of the Nile should turn aside into this Arabian gulf, what would hinder that gulf from being filled up with silt as the river continued to flow, at all events within a period of twenty thousand years?
There it loosens the silt or sand, and runs out, leaving cavities that cause the clay above to break, and run down in lumps and disturbed streams.
The ground above the frames is remarkably good, but under it there is a stratum of silt which breaks and falls in large masses.
In consequence of this continued displacement of thesilt and clay, a cavity had been formed above the staves.
It is evident [from a flow of silt which had taken place on that day] that with the shield we have passed close under a body of collected water a few inches only above the staves.
It was found impossible to get into the frames, as a mound of clay and silt closed the entrance.
It is astonishing how the silt resists the sliding of the top staves.
As the year drew to a close, the difficulty of working the silt increased, and with this difficulty increased also the expense of maintaining the staff of men required.
All this land was the south rim of the silt dam, which extended from the line of cliffs or mesa on the east to the mountains on the west.
The entire stream, instead of pushing slowly across the delta, weltering in its own siltto the Gulf, poured into the bottom of the basin nearly four hundred feet below the top of this silt-made dam.
Without a forest cover, rain runs off mountain slopes very rapidly, often carrying with it silt and sand, and, in severe floods, even rocks and bowlders.
Many streams in the West carry such enormous amounts of silt that the storage capacity of reservoirs has been seriously impaired, even within a comparatively short time.
This piling up of mounds has been caused by clearing the silt from the entrance to the intake of the canal.
And fishes and ferns, monsters and moss were occasionally caught in the flowing deposits of lime and sand and silt and clay, and were embedded in their mass.
Another interesting question here arises: "What became of the vast quantity of sand and silt and pebbles that formed and were carried away during such a gigantic process?
Mars had been dusty, a waste of reddish sand and desert silt that made the Sahara seem like paradise, and it had settled on his spacesuit, to come in through the airlocks with him.
Bill looked down at the bed to see a fine film of Moon silt there.
The bluntnose minnow preferred the clearer creeks, with gravel or gravel-silt bottoms, but occurred rarely in the mainstream of the Big Blue River.
The larger pools of gravelly streams were preferred by johnny darters, but one specimen was taken from the main stream of the Big Blue River, and the species was abundant in one stream over hard, sand-silt bottom.
Silt then enormously aggravates the situation, for the sand will collect against the obstruction until it becomes a miniature sandbank.
For instance, in the case of a ship sunk in a narrow channel where much silt is experienced, the explosive method is almost worse than useless.
And a ship which grounds in a locality affected by silt will have sand deposited against her sides much to the detriment of salvage operations.
It will therefore be seen that, where a channel is artificially cut on the floor of the sea, silt will continually tend to fill that channel again until the bottom is level once more.
When first designed the open viaduct was of shorter length than that eventually constructed; the alteration was considered necessary after local experience of the silt had been obtained.
Silt may be defined as the movement of sand or mud, according to the nature of the sea bottom in the {24} locality, due to current.
