But wind and wave and alluvium working together choke these communications, and directly the mouth seawards of a lagoon is closed it is converted into a stagnating marsh that exhales malaria.
At every overflow eighteen thousand cubic yards of alluvium was deposited over this district, all of which is now carried into the Mediterranean and thrown down in the construction of new bars; utterly wasted.
The alluvium is deposited, banks multiply, the mouths are encumbered with submarine islets, locally called theys, which the waves and currents of the sea displace and remodel continuously, and render the entrance to the river impracticable.
Even the alluvium deposits along the banks of the rivers and their tributaries, as well as the river beds, might, in many instances, be found to "pay.
In this matter theory must bow to "rule of thumb:" the caprices of alluvium are various and curious enough to baffle every attempt at scientific induction.
Where the sand in the lagoons and estuaries is more or less mingled with the alluvium brought down by the rivers, there are plants of another class which are equally characteristic.
A piece which was dug out of the alluvium within a few miles of Ratnapoora in 1853, was purchased by a Moor at Colombo, in whose hands it was valued at upwards of four thousand pounds.
Molybdena is found in profusion dispersed through many rocks in Saffragam, and it occurs in the alluvium in grey scales, so nearly resembling plumbago as to be commonly mistaken for it.
The first is, that the organic remains found in the alluvium considerably above the drift, which always lies below the alluvium, are many of them of extinct species.
Russian miner of the finding of a mass of meteoric iron in the auriferous alluvium of the Altai.
Between the superficial covering of vegetable mould and the subjacent rock there usually intervenes in every district a deposit of loose gravel, sand, and mud, to which the name of alluvium has been applied.
Our next inquiry may be directed to the alluvium strewed over the surface of the supposed area of denudation.
In almost every country, the alluvium consists in its upper part of transported materials, but it often passes downwards into a mass of broken and angular fragments derived from the subjacent rock.
Before concluding my remarks on the northern drift of the Old World, I shall refer to a fact recently announced, the discovery of a meteoric stone at a great depth in the alluvium of Northern Asia.
In many cases, the alluvium in which rivers are now cutting their channels, originated when the land first rose out of the sea.
In corroboration of this view, they contended that the alluvium of Glen Roy, as well as of other parts of Scotland, agrees in character with the moraines of glaciers seen in the Alpine valleys of Switzerland.
Catalonia, and before the formation of an alluvium (d) of unknown date.
It was a picturesque spot, and the Northra is typical of the smaller rivers of the country, the valley filled with alluvium and the river meandering through it, though when in flood not much of the alluvium can be seen.
Along the Hvita (white river) valley there were many evidences that the river had at one time been far wider, for up the valley sides several terraces marked levels at which alluvium had formerly been deposited.
We soon passed from the alluvium to the lava-field around Eldborg, and then ascended by a gradual slope to the foot of the volcano, which is a mere ring of green scoria.
The object of the engineer is so to utilize this flood-water that as little as possible of the alluvium may escape into the sea, and as much as possible may be deposited on the fields.
The second is hardly less valuable, and consists in the remarkable richness of the alluvium brought down the river year after year during the flood.
This alluvium consists of gravel firmly cemented with mud and clay, and is unquestionably water-tight.
The only plan was to dump down in the valley an earthen dam, making it very broad so as to distribute the weight over as large a space as possible of the alluvium underneath.
A trickle of water flows down to become lost in the alluvium of the lower part of the valley or to reappear in scattered springs.
Patches of alluvium or playas, as they are locally called, continue as far as Santo Anato, but they are cultivated only as far as Rosalina.
Toward the lower end of the canyon a little finer alluvium appears and settlement begins.
A thick deposit of terraced alluvium may be seen on the valley floor, and it is on one of the lower terraces that the city of Cotahuasi stands.
If the alluvium is coarse and steeply inclined there is only pasture on it or a growth of scrub.
Finally, after a tumble of three thousand feet over countless rapids the river emerges at Colpani, where an enormous mass of alluvium has been dumped.
In such an event it would not be possible to distinguish between alluvium and till.
Only in the most highly favored places where a small bench or a patch of alluvium occurs may one find even an isolated dwelling.
A few miles above Aplao the stream emerges from its narrow gorge and thenceforth flows on the surface of the alluvium right to the sea.
Fine alluvium is represented by small closely spaced dots; coarse alluvium by large closely spaced dots.
Account for the flat rock floors on which these deposits of alluvium rest.
They cut through the alluvium of their flood plains, leaving it on either bank as successive terraces, and intrench themselves in the underlying rock.
River Terraces of Rock covered with Alluvium c, recent flood plain of the river.
Flood plains may consist of a thin spread of alluviumover the flat rock floor of a valley which is being widened by the lateral erosion of a graded stream (Fig.
Buildings on firm rock suffered least, while those on deep alluvium were severely shaken by the undulations, like water waves, into which the loose material was thrown.
What is the age of rock-cut valley and of the alluvium which partially fills it, compared with that of the Kansan till?
Like the recent alluvium of the Great Valley of California (p.
Account for thealluvium at a and b and on the opposite side of the valley at the same levels.
And in search of such locations we must account for the numberless shafts which still exist both in India and Peru, and sometimes sunk within a few feet of each other, passing through the alluvium to a depth of 40 feet to the bed rock.
This alluvium forms one of the deepest and richest soils in the world.
The water has somewhat of an unctuous appearance, as if overcharged with contributions of the very fattest alluvium from all parts of Yorkshire.
The alluvium is here cut into a cliff, ten or twelve feet above the bed of the river, and against it the sand is blown in naked dunes.
A strong current four or five miles broad, of muddy water, flows between a precipitous bank of alluvium or sand on one side, and a flat shelving one of sand or more rarely mud, on the other.
We traversed the empty bed of a mountain torrent, with perpendicular banks of alluvium 30 feet high, and thence plunged into a dense forest.
The contrast between the fertility of the alluvium and the sterility of the protruded quartzy rocks is very striking, cultivation running up to these fields of stones, and suddenly stopping.
The alluvium on the banks of the Ganges is obviously an aqueous deposit subsequent to the elevation of these hills, and is perfectly plane up to their bases.
I have elsewhere remarked that the alluvium of the Gangetic valley may to a great degree be the measure of the denudation which the Himalaya has suffered along its Indian watershed.
That thealluvium absorbs the heat better, and retains it longer, would appear from the following, the only observations I could make, owing to the tenacity of the soil.
The mass of Shan-tung thus forms a mountainous island rising out of the vast alluvium of the Hwang-Ho, whose discharge into the sea has alternated between the north and the south of that mountainous tract.
The object of the Kashmírí is to raise as much rice as he possibly can on the alluvium of his valley and on the rich soil deposited on the banks of mountain streams.
The Alluvium was distinguished from Diluvium by the fact that its mammalian fossils were representatives of still living forms, but it is a matter of great difficulty to separate these two divisions in practice.
Like the recent alluvium of the Great Valley of California, these deposits imply low-lying lands when they were laid, and therefore at that time the mountains rose from near sea level.
Abbott speaks of the finding of such implements in the glacial alluvium of the Delaware (Figs.
These implements are found not only in the alluvium as are the Chelleen COUPS DE POING, but also in the cave or rock-shelter deposits.
The latter seems never to have been seen before in the old alluvium of France.
In the "Principles of Geology," when treating of the fossil remains found in alluvium and the mud of caverns, I gave an account in 1832 of the investigations made by MM.
We also find that the older alluvium contains the remains of Mastodon everywhere, and in some places, as at Evansville, those of the Megalonyx.
Having offered these general remarks on the alluvium of the Thames, I may now say something of the implements hitherto discovered in it.
The valley of the Seine is not only geographically contiguous to the valley of the Somme, but its ancient alluvium contains the same mammoth and other fossil species.
Mr. Prestwich has suggested that ground-ice may have had its influence in modifying the ancient alluvium of the Somme.
They have also been traced far up the valley above Amiens, wherever patches of the old alluvium occur.
The most marked feature of this alluvium in the Thames valley is that great bed of ochreous gravel, composed chiefly of broken and slightly worn Chalk flints, on which a great part of London is built.
Flint Implements in ancient Alluviumof the Basin of the Seine.
