Gravels Sentence Examples
Other precious stones, including the sapphire, emerald, oriental emerald, ruby, opal, amethyst, garnet, chrysolite, topaz, cairngorm, onyx, zircon, etc., have been found in the gold and tin bearing drifts and river gravels in numerous localities throughout the states.
All these are wanting in the Pacific area, though there are indications in its gold-bearing gravels that it once possessed them.
The earlier wells in Pennsylvania consisted of three sections, the first formed of surface clays and gravels, the second of stratified rocks containing water, and the third of stratified rocks, including the oil-sands, usually free from water.
They have also been found in Pleistocene gravels in several parts of England, as Maidenhead, Bromley, Freshfield near Bath, Barnwood near Gloucester, and in the brick-earth of the Thames valley at Crayford, Kent; while their remains also occur in Arctic America.
The gold-bearing gravels of East Siberia, especially those of the Lena and the Amur, are relatively more prolific than those of West Siberia.Advertisement
It is also found in the form of rolled lumps and grains, "stream tin," in alluvial gravels; the latter are secondary deposits, the products of the disintegration of the first-named primary deposits.
Permeability is practically identical with the speed at which percolation takes place; through clay it is slow, but increases in rapidity through marls, loams, limestones, chalks, coarse gravels and fine sands, reaching a maximum in soil saturated with moisture.
The " pan " is now only used by prospectors, while the " cradle " and " tom " are practically confined to the Chinese; the sluice is considered to be the best contrivance for washing gold gravels.
Even the Calaveras man is no exception, since his skull and his polished conical pestle, the latter made of stone more recent than the auriferous gravels, show him to have been of Digger Indian type.
In North America the sites have been examined by the Peabody Museum, the Bureau of American Ethnology, and others, with the result that only the Trenton gravels have any standing.Advertisement
The latter was a gigantic animal, especially during the Pleistocene period; the skulls and limbbones discovered in the brick-earths and gravels of the Thames valley and many other parts of England having belonged to animals that probably stood six feet at the shoulder.
The most active operations are carried on in Florida, where the phosphate was first worked in 1887 in the form of pebbles in the gravels of Peace River.
In Westland the Miocene includes the Moutere gravels, which rest on the summit of Mount Greenland, 4900 ft.
Valley gravels .border the Thames, and Pleistocene mammalia have been found in fissures in the Hythe beds at Ightham, where ancient stone implements are common.
Denudation in earliest Eocene times has produced flint gravels above the chalk, and an ancient stream deposit of chalk pebbles occurs at Ballycastle.Advertisement
Glacial gravels are well seen near Antrim town, and as drumlins between Ballymena and Ballycastle.
Recently elevated marine clays, of post-glacial date, fringe the south-eastern coast, while gravels with marine shells, side by side with flint implements chipped by early man, have been lifted some 20 ft.
The central section of the plains thus presents a marked contrast to the northern section; for while the northern section owes its smoothness to the removal of local gravels and sands from a formerly uneven surface by the action of degrading rivers and their inflowing tributaries, the southern section owes its smoothness to the deposition of imported gravels and sands upon a previously I uneven surface by the action of aggrading rivers and their outgoing distributaries.
Gold occurs in quartz veins traversing various formations (some as young as Jurassic), and also in gravels, which were for the most part deposited previous to the uplift of the Sierra block.
Some of the gravels then occurred as piedmont deposits along the western border of the old mountains; these gravels are now more or less dissected by new-cut valleys.Advertisement
Other auriferous gravels are buried under the upland lava flows, and are now reached by tunnels driven in beneath the rim of the table mountains.
The reputed discovery of traces of early man in the lava-covered gravels has not been authenticated.
The Lafayette formation has been the occasion of much difference of opinion, but is by many held to be a non-marine formation, made up of gravels, sands and clays, accumulated on land, chiefly through the agency of rain and rivers.
On the coastal plain there is the Columbia series of gravels, sands and barns, made up of several members.
Old alluvial deposits are left high above the existing level of many rivers, in the form of "terraces" of gravel and loam, the streams to which these owe their existence having modified their courses and cut deeper channels; such are the alluvial gravels and brick-earths upon which much of "greater London" is built.Advertisement
Limonite often forms a cementing medium in ferruginous sands and gravels, forming "pan"; and in like manner it is the agglutinating agent in many conglomerates, like the South African "banket," where it is auriferous.
The hills on the right bank Geology, of the Tiber culminating in Monte Mario (455 ft.) belong to the first of these, being of the Pliocene formation; they consist of a lower bluish-grey clay and an upper group of yellow sands and gravels.
Numerous isolated palaeolithic objects of the Mousterian type have been found in the neighbourhood of Rome in the quaternary gravels of the Tiber and Anio; but no certain traces of the neolithic period have come to light, as the many Pre" flint implements found sporadically round Rome pro- historic bably belong to the period which succeeded neolithic (called by Italian archaeologists the eneolithic period) inasmuch as both stone and metal (not, however, bronze, but copper) were in use.
The majority of minerals are found commonly in masses which can with difficulty be recognized as aggregates of crystalline grains, and occur comparatively seldom as distinct crystals; but the diamond is almost always found in single crystals, which show no signs of previous attachment to any matrix; the stones were, until the discovery of the South African mines, almost entirely derived from sands or gravels, but owing to the hardness of the mineral it is rarely, if ever, water-worn, and the crystals are often very perfect.
The diamond is here found in ancient sandstones and conglomerates, and in the river gravels and sands derived from them.
Since the heavy minerals of the cascalho in the river beds are more worn than those of the terraces, it is highly probable that they have been derived by the cutting down of the older river gravels represented by the terraces; and since in both deposits the heavy minerals are more abundant near the heads of the valleys in the plateau, it is also highly probable that both have really been derived from the plateau deposit.
The diamond here occurs in river gravels and sands associated with the same minerals as in Minas Geraes; since 1844 the richest mines have been worked in the Serra de Cincora, where the mountains are intersected by the river Paraguassu and its tributaries; it is said that there were as many as 20,000 miners working here in 1845, and it was estimated that 54,000 carats were produced in Bahia in 1858.
These " dry diggings " were therefore at first supposed to be alluvial in origin like the river gravels; but it was soon discovered that, below the red surface soil and the underlying calcareous deposit, diamonds were also found in a layer of yellowish clay about 50 ft.
African locality must be mentioned.; considerable finds were reported in 1905 and 1906 from gravels at Somabula near Gwelo in Rhodesia where the diamond is associated with chrysoberyl, corundum (both sapphire and ruby), topaz, garnet, ilmenite, staurolite, rutile, with pebbles of quartz, granite, vIII.
But in the " Drift " maps many other types of deposit are indicated, such, for instance, as the ordinary modern alluvium of rivers, and the older river terraces (River-drift of various ages), including gravels, brickearth and loam; old raised sea beaches and blown-sand (Aeolian-drift); the " Head " of Cornwall and Devon, an angular detritus consisting of stones with clay or loam; clay-with-flints, rainwash (landwash), scree and talus; the " Warp," a marine and estuarine silt and clay of the Humber; and also beds of peat and diatomite.
It is probable that certain rudely chipped flints, so-called eoliths, in the alluvial gravels (formed generally at the mouth of wadis opening on to the Nile) at Thebes and elsewhere, are the work of primitive man; but it has been shown that such are produced also by natural forces in the rush of torrents.
Above the Boulder Clay are found sands and gravels, along with perched boulders which, by their source and position, indicate the direction and thickness of the ice that carried them.
The " flume " enabled him to dry the bed of a stream while he worked over its gravels.
The hydraulic stream came into use as early as 1852 (or 1853) when prospecting of the higher ground made it certain that the " deep " or " high " gravels - i.e.
Its most interesting feature is the occurrence near its summit, north of Cape Mondego, of sands and gravels containing plant remains.
Bones and implements have been found in the Quaternary gravels at Trenton, which have been held by some authorities to prove the presence of Palaeolithic man; but the earliest inhabitants of New Jersey of whom there is any certain record were the Lenni-Lennape or Delaware Indians, a branch of the Algonquian family.
This boulder clay covers almost all the low ground north of the Thames Basin, its southern margin fading away into washed sands and gravels.
The London Basin occupies a triangular depression in the Chalk which is filled up with clays and gravels of Tertiary and later age.
The last well-marked lowering of the land took place in the Pleistocene period, when it was accompanied by glacial conditions, through which the greater part of northern England and the Midlands was covered by ice; a state of things which led directly and indirectly to the deposition of those extensive boulder clays, sands and gravels which obscure so much of the older surface of the country in all but the southern counties.
There seem to have been two periods of eruption, and as some of the lavas have flowed over Quaternary gravels, the latest outbursts must have been of very recent date.
Many interesting mammalian fossils, rhinoceros, mammoth, &c., with palaeolithic implements, have been found in the valley gravels of the river Ouse and its tributaries.
Speaking generally, the Ozark region is characterized by reddish clays, mixed with gravels and stones, and cultivable in inverse proportion to the amount of these elements; northern Missouri by a generally black clay loam over a clay subsoil, with practically no admixture of stones; the southern prairies, above referred to, share the characteristics of those north of the Missouri.
High-level gravels occur from 600 to 2000 ft.
The Biggleswade well was sunk by processes better known in connexion with the sinking of mine shafts and foundations of bridges across the deep sands or gravels of bays, estuaries and great rivers.
Flint gravels are widely employed for dressing walks and roads, and for rough-cast work in architecture.
The more deep-seated type of these rocks is seen in the olivine-gabbro mass of Carlingford Mountain; but most of the igneous region became covered with sheets of basaltic lava, which filled up the hollows of the downs, baked the gravels into a layer of red flints, and built up, pile upon pile, the great plateaus of the north.
Volcanic activity may have extended into Miocene times; but the only fossiliferous relics of Cainozoic periods later than the Eocene are the pale clays and silicified lignites on the south shore of Lough Neagh, and the shelly gravels of pre-glacial age in county Wexford.
Boulder-clays and sands, and gravels rearranged by water, occur throughout the lowlands; while the eskers or " green hills," characteristic grasscovered ridges of gravel, rise from the great plain, or run athwart valleys and over hill-sides, marking the courses of sub-glacial streams. When the superficial deposits are removed, the underlying rocks are found to be scored and smoothed by ice-action, and whole mountain-sides in the south and west have been similarly moulded during the Glacial epoch.
The underlying bedrock is chalk, with overlying river gravels.
The flint artifacts found in the ancient river gravels are frequently rolled, battered, and stained brown by iron oxides.
The pit also has glacial gravels at the top from the Pleistocene.
These are river bed gravels mixed with lime to give the mortar strength.
Here organic material, channeled into gravels has yielded fossil mammals including hippopotamus.
The high yield in gravels may make the method impractical.
They can consist of clays, muds, sands or gravels or a mixture of these, often cemented together by iron oxides.
The underlying geology is a gray shaly metamorphosed limestone, perhaps turbidite, interbedded with sandstone; sands and gravels fill the valleys.
The freely draining impoverished ands and gravels support a very simple flora which is dominated by ling and bell heather.
The sands and gravels of the alluvial plain originated as glacial outwash from the melting glaciers inland.
These gravels are more resistant to scour and can maintain higher slope angles than the estuarine silts and clays.
Other precious stones, including the sapphire, emerald, oriental emerald, ruby, opal, amethyst, garnet, chrysolite, topaz, cairngorm, onyx, zircon, &c., have been found in the gold and tin bearing drifts and river gravels in numerous localities throughout the states.
Few of the mountain creeks succeed in reaching the arid plains, and those that do quickly disappear by evaporation or by seepage into the gravels.
The coarser particles of the sediments are deposited near the shore as gravels, sand and muds, but the very fine particles remain in suspension in the colloidal form, and some of this may be acted upon by marine bacteria or (it is surmised) even utilized by diatoms as a source of silica.
They include the gravels and alluviums of the present streams and the almost ubiquitous red sand of aeolian origin.'
The floor of this depression being below baselevel, it has necessarily come to be the seat of the mountain waste brought down by the many streams from the newly uplifted Sierra Nevada on the east and the coast ranges on the west; each stream forms an alluvial fan of very gentle slope; the fans all become laterally confluent, and incline very gently forward to meet in a nearly level axial belt, where the trunk riversthe Sacramento from the north and the San Joaquin from the south-east--wander in braided courses; their tendency to aggradation having been increased in the last half century by the gravels from gold washing; their waters entering San Francisco Bay.
The washing of the high or Tertiary gravels by the hydraulic process and the working of mines in the solid rock did not, on the Gold and whole, compensate for the diminished yield of the Silver ordinary placer and river diggings, so that the product of gold in California continued to fall off, and by 1860
The Bagshot Beds in the west form infertile tracts of sandy soil, covered with heath and pine, where space is available for the great camps and military training-grounds round Aldershot, and for the extensive cemeteries at Woking The London Clay in the east is more fertile and crowded with villages, while the East Anglian portion of the basin consists of the more recent Pliocene sands and gravels, which mix with the boulder clay to form the best wheat-growing soil in the country.
Lower estuary sands and gravels are well-sorted and their very low percentage of heavy metals implies little input of terrigenous sediment.