How to use Clays in a sentence
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.
Clays of all qualities and colours abound.
The best soils are in the west section, where limestone clays or shell marls are common.
It is marked by grey clays and sands, lignitic fossiliferous clays, beds of lignite or brown coal, sometimes 8 ft.
The latest Cretaceous is the Ripley formation, which lies west of the northern part of the last-named, and, about Scooba, in a small strip, the most southerly of the Cretaceous - it is composed of coarse sandstones, hard crystalline white limestones, clays, sands, phosphatic greensands, and darkcoloured, micaceous, glauconitic marls; its greatest thickness is about 280 ft.Advertisement
The Jackson formation south-west of the Lisbon beds, is made up chiefly of grey calcareous clay marls, bluish lignitic clays, green-sand and grey siliceous sands.
They yield valuable coals, clays, marls and ganister.
Sandy soils are made thereby too dry and leachy, and it is a questionable proceeding to turn the heavy clays upon the top. Planters are, as a result, divided in opinion as to the wisdom of subsoiling.
Eastwards the mountain system, the Jebel Sangeli, maintains the same general character as far as Bandar Gori (Las Korai), where the precipitous northern cliffs approach within 200 or 300 yards of the gulf, their bare brown rocks and clays presenting the same uninviting appearance as the light brown hills skirting the Red Sea.
Tobacco is most generally cultivated on loose red soils, which are rich in clays and silicates; and sugar-cane preferably on the black and mulatto soils; but in general, contrary to prevalent suppositions, colour is no test of quality and not a very valuable guide in the setting of crops.Advertisement
Even in the soils which farmers speak of as stiff clays it is rarely present to the extent of more than I or 2%.
Where the soil grains are quite free from each other the smaller grains tend to fill up the spaces between the larger ones; hence it might be concluded that in clays the amount of pore-space would be less than in coarser sands.
This is the case in " puddled " clays, but in ordinary clay soils the excessively minute particles of which they largely consist tend to form groups of comparatively large composite grains and it is in such natural soils that the pore-space is largest.
In certain sandy soils and in a few stiff clays it may amount to less than 4%, while in others in limestone and chalk districts there may be 50 to 80% present.
It tends to improve the tilth and the capillarity of the soil by binding sands together somewhat and by opening up clays.Advertisement
The addition of small quantities of lime, especially in a caustic form, to stiff greasy clays makes them much more porous and pliable.
It is this power of creating a more crumbly tilth on stiff clays that makes lime so valuable to the farmer.
Generally speaking light poor lands deficient in organic matter will need the less caustic form or chalk, while quicklime will be most satisfactory on the stiff clays and richer soils.
The oldest rocks of Barbados, known as the Scotland series, are of shallow water origin, consisting of coarse grits, brown sandstones and sandy clays, in places saturated with petroleum and traversed by veins of manjak.
Sandstone, and clays suitable for brick-making, are found in the district of Scotland, so called from a fancied resemblance to the Highlands of North Britain.Advertisement
He died in 1427, at the age of seventy-six, in the seclusion of the temple where he had passed the whole of his clays.
The soft shales or clays of the hills bounding the valley render these hills especially subject to the action of denudation, and the result, in rounded slopes and easily accessible crests, determines the nature of the easy tracks and passes which intersect them.
Those of economic value are kaolin, mined chiefly in the vicinity of Hockessin, New Castle county, the static kaolin product being exceeded in 1903 only by that of Pennsylvania among the states of the United States; granite, used for road-making and rough construction work, found near Wilmington; and brick and tile clays; but the value of their total product in 1902 was less than $500,000.
The actual coal measure strata, consisting mainly of shales and clays, are generally impervious to water, but when strata of a permeable character are sunk through, such as the magnesian limestone of the north of England, the Permian sandstones of the central counties, or the chalk and greensand in the north of France and Westphalia, special methods are required in order to pass the water-bearing beds, and to protect the shaft and workings from the influx of water subsequently.
Geologically the region is made up of Carboniferous limestones, clay slates and sandstones, containing anthracite and coal; of Cretaceous marls, chalk, sandstone and greensands - chalk cliffs, in fact, accompany the Don for 200 m.; and of Miocene limestones and clays.Advertisement
Whilst pyrites is found abundantly in the older crystalline rocks and slates, marcasite is more abundant in clays, and has often been formed as a concretion around organic remains.
Sometimes the phosphate is found at the surface, but generally it is covered by alluvial sands and clays.
There are also deposits of clay suitable for making bricks, terra-cotta and tiles in nearly every county outside of this valley, and there are some pottery clays in Albany and Onondaga counties.
There are large deposits of glacial and residual clays and clay shales throughout the state.
The valley, which extends from the borders of Sussex to Hythe, is occupied chiefly by the Weald clays, which contain a considerable number of marine and freshwater fossils.Advertisement
The sands and clays found here are fine and soft, and as there is scant vegetation to protect the hillsides they are easily eroded by the rains.
Good clays for the manufacture of tile and brick are found at numerous places.
Near Luang Prabang, just beyond the border, in French territory, limestones with Productus and Schwagerina, like the Productus limestone of the Indian Salt Range, have been found; also red clays and grauwacke with plants similar to those of the Raniganj beds; and violet clays with Dicynodon, supposed to be the equivalents of the Panche series of India.
Brick, potter's and tile clays are obtained most largely along the west border of the Coastal Plain, and fire-clay from the coal region of West Maryland; in 1907 the value of clay products was $1,886,362.
The former consists of sandstones and clays, and the fossils found in.Advertisement
Associated with these irregular escarpments are occasional rectilinear ridges, the work of extensive erosion on monoclinal structures, of whick Echo Cliffs, east of the Painted Desert (so called from its manycoloured sandstones and clays), is a good example.
Another consequence of revived erosion is seen in the occurrence of great landslides, where the removal of weak (Permian) clays has sapped the face of the Vermilion Cliffs (Triassic sandstone), so that huge slices of the cliff face have slid down and forward a mile or two, all shattered into a confused tumult of forms for a score or more of miles along the cliff base.
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.
Round it the Palaeozoic sands and clays, largely derived from its own waste, were deposited as nearly horizontal beds, in many places still almost undisturbed.
North of the mineral region is the "Cereal Belt," embracing the Tennessee Valley and the counties beyond, whose richest soils are the red clays and dark loams of the river valley; north of which are less fertile soils, produced by siliceous and sandstone formations.Advertisement
The soft limestone underlying this region is covered, in the uplands, with grey, sandy soils, which have a subsoil of loam; in the lowlands the surface soils are loams, the subsoils clays.
Aluminium silicate is the chemical body of which all clays are nominally composed.
Kaolin or China clay is essentially a pure disilicate (Al 2 O 3.2SiO 2.2H 2 O), occurring in large beds almost throughout the world, and containing in its anhydrous state 2 4.4% of the metal, which, however, in common clays is more or less replaced by calcium, magnesium, and the alkalis, the proportion of silica sometimes reaching 70%.
Forming the basis of all clays, aluminium silicates play a prominent part in the manufacture of pottery and porcelain.
It is believed that the bluish colour of many clays and limestones is referable to the presence of finely divided pyrites, and it is known that certain deposits of blue mud now forming around continental shores owe their colour, in part, to disseminated iron sulphide.Advertisement
No Permian beds are known, and for many years Mesozoic deposits were supposed to be entirely absent, but Triassic clays and sandstones with Daonella have been found in the upper part of the basin of the Kwalu (East Sumatra).
At Trezza, on the eastern base of the mountain, basaltic rocks occur associated with fossiliferous Pliocene clays.
The earlier period is characterized by the practice of inhumation in harrows made of clays, stones or sand, according to the district.
The extremely primitive writing of those clays was quite incapable of rendering such minute differences as can have existed between the pronunciation of Mecca and that of Medina.
In the Kharga Oasis the upper portion consists of variously colored unfossiliferous clays with intercalated bands of sandstone containing fossil silicified woods (Nicolia Aegyptiaca and A raucarioxylon Aegypticum).Advertisement
They are conformably overlain by clays and limestones with Exogyra Overwegi belonging to the Lower Danian, and these by clays and white chalk with Ananchytes ovata of the Upper Danian.
It is rich, however, in clays, while in the island of Bornholm there are quarries of freestone and marble.
The beds are reached by sinking through the clays and variegated marls typical of this formation.
Crystalline rocks crop out at several capes; Cretaceous limestones, containing an abundant and specific fauna of gigantic ammonites, occur at Dui on the west coast, and Tertiary conglomerates, sandstones, marls and clays, folded by subsequent upheavals, in many parts of the island.
The clays, which contain layers of good coal and an abundant fossil vegetation, show that during the Miocene period Sakhalin formed part of a continent which comprised north Asia, Alaska and Japan, and enjoyed a comparatively warm climate.
Being composed largely of red clays and laterite, the soil is not generally rich, and calls for the patient cultivation of the Chinese gardener to make it really productive.
Fars series; marls, clays and sand stones with limestones and inter bedded strata of rock gypsum.
Extremely valuable and varied marls, kaolins and clays, fuller's earth, asphaltum and mineral waters show special promise in the state's industry.
Gold, petroleum, copper, borax and its products, clays, quicksilver and silver lead, in order of importance, representing some fourfifths of the total.
The small development of Upper Carboniferous strata, visible on the shore south of Corrie and in Ben Lister Glen, consists of sandstones, red and mottled clays and purple shales, which yield plantremains of Upper Carboniferous facies.
Marshy soils are found along the lowest portions of the Coastal Plain, and are exceedingly productive wherever reclaimed by draining, as in portions of the Dismal Swamp. Other portions of the Coastal Plain afford more valuable soils, sandy loams overlying sandy clays.
The former of these, representing the bottommoraine of the ice-sheet, are covered with Glacial and post-Glacial clays (partly of lacustrine and partly of marine origin) only in the peripheral coast-region - or in separate areas in the interior depressions.
The surrounding country is a magnificent livestock and farming region, and in the immediate vicinity are valuable deposits of coal, of limestone, of shale suitable for sewer pipe and of fire clays.
In places sands and clays overlie the glacial deposits.
Sands (mosand) and clays (akerlera and fucuslera) continued to be deposited on the lower parts of the country.
It produces abundance of seeds, and is easily raised, but it requires good and tolerably dry soil; it will not thrive on stiff clays nor on dry sands or chalks.
Where this intervening band is not covered by recent gravel deposits, it exhibits beds of limestone, clays and sandstone with fossils, which, in age, range from the Lower Eocene to the Miocene.
Along the Colorado is the Painted Desert, remarkable for the bright colours - red, brown, blue, purple, yellow and white - of its sandstones, shales and clays.
Coalbearing clays containing fresh-water molluscs and dicotyledonous plants, as also conglomerates, alternate with the sandstones in these Tertiary deposits.
In New Jersey the mining of clays is more important than in any other state, the amount mined and sold in 1902 being a third of the entire output of the United States, and the amount in 1907 (44 0, 1 3 8 tons) being more than one-fifth of all clay mined and sold in the United States; and in 1907 in the value of clay products ($16,005,460; brick and tile, $9,019, 834, and pottery, $6,985,626) New Jersey was outranked only by Ohio and Pennsylvania.
Much of the raw material for this industry, such as ball, flint, and spar clays and kaolin, is imported from other states.
In exactly the same way the whole of the south-east of the island appears to have been covered uniformly with gently dipping beds of Tertiary sands and clays, beneath which the Cretaceous strata dipped.
Each group is made up of an alternation of soft marls or clays and hard limestones or sandstones.
The London Basin occupies a triangular depression in the Chalk which is filled up with clays and gravels of Tertiary and later age.
Closely following the same line are the alternating clays and limestones of the Oolitic series.
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.
Fireclay is largely raised from coal-mines, while, among special clays, there is a considerable production of china and potter's clays in Cornwall, Devonshire and Dorsetshire.
The Great Ouse, from the point where it enters the county on the west, has carved through the Middle Oolites and exposed the Great Oolite as far as Bedford; their alternating limestones and clays may be seen in the quarries not far from the town.
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.
Coal, lead, zinc, clays, building stones and iron are the most important minerals.
Clays occur in amounts and varieties surpassed by the deposits in very few if any states of the Union.
They are in every form from the rare to the common-glass pot clay, ball clays, kaolins, flint fireclays, plastic fireclays, stone-ware clays, paving-brick shales, building-brick and gumbo clays.
Plastic fireclays, paving and brick clays are available in seemingly limitless quantities.
Clays occur, in short, all over the state; and their use is almost as general.
The finer clays, also, are mainly shipped from the state in natural form, but in the manufacture of sewer-pipe and fire-brick, Missouri is a very prominent state.
Nearly all clays, notably those from the Glacial deposits, naturally contain sand and stones, 40 to 50% by weight of which is not too much if uniformly distributed an y 1 if the clay is otherwise good.
The finer particles of clay in the line of the joint are washed away, while the sandy particles, which nearly all natural clays contain, remain behind and form a constantly deepening porous vein of sand crossing the base of the puddle.
Pottery, fire, ochre and brick clays are abundant, the first two mainly in the eastern part of the state.
The great number of streams of large volume is due to the moist climate and the abundance of glaciers, and the milky white or yellowish-brown colour of their waters (whence the common name Hvita, white) is due to the glacial clays.
In small quantities, vanadium is found widely distributed, the chief sources being vanadite, mottramite, descloizite, roscoelite, dechenite and pucherite, whilst it is also found as a constituent of various clays, iron-ores and pitchblendes.
Probably its original thickness Lough Neagh Tertiary Clays Eocene Basalt and Dolerite Cretaceous Trias, sometimes surmounted by Lower Jurassic Upper Carboniferous Carboniferous was not more than 150 ft., while now only from 40 to loo ft.
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.
Clays of various kinds, mainly fire and brick clay, are obtained in several places and there are quarries of marble (notably in Connemara), slate, granite, limestone and sandstone, the output of which is considerable.
The lower members of the Cretaceous series include an important fresh-water formation (sandstones and clays), which extends from the Cantabrian coast through the provinces of Santander, Burgos, Soria and Logrono, and is supposed to represent the English Wealden series.
They have left behind them thick deposits of clays, marls, gypsum and limestone, in which numerous remains of the land-animals of the time have been preserved.
The state, however, is particularly rich in good clays, which are probably its greatest mineral resource.
Its clays which are of all colours, are the most valuable of the state.
Ctenozamites occurs chiefly in the Rhaetic coal-bearing beds of Scania, and has been found also in the Liassic clays of FIG.
This lignite and the accompanying leaf-bearing clays underlie and are apparently older than the strata with Newer Pliocene mammals and mollusca.
Limestone, for the reduction of lime, is also mined; and beryl, clays and mineral springs yield products of minor importance.
In nature, clays are rarely free from foreign ingredients, many of which can be detected with the unaided eye, while others may be observed by means of the microscope.
Natural clays, even when most pure, show a considerable range of composition, and hence cannot be regarded as consisting of a single mineral; clay is a rock, and has that variability which characterizes all rocks.
If any rock be taken (even a piece of pure quartz) and crushed to a very fine powder, it will show some of the peculiarities of clays; for example, it will be plastic, retentive of moisture, impermeable to water, and will shrink to some extent if the moist mass be kneaded, and then allowed to dry.
Hence sands are more coarse grained than clays.
Clays consist essentially of the above ingredients (although serpentine is not known to take part in them to any extent, it is closely allied to chlorite).
Most clays are waterborne, having been carried from the surface of the land by rain and transported by the brooks and rivers into lakes or the sea.
For these reasons the principal gathering places of fine pure clays are deep, still lakes, and the sea bottom at considerable distances from the shore.
Microscopic sections of some of the more coherent clays and shales may be prepared by saturating them with Canada balsam by long boiling, and slicing the resultant mass in the same manner as one of the harder rocks.
These results are confirmed by the mechanical analysis of clays.
Some of them contain much iron (yellow, blue and red clays); others contain abundant calcium carbonate (calcareous clays and marls).
Pure clays, however, may be found almost quite free from these substances.
Alumina is high in the finer clays (18 to 30%), and they are the most aluminous of all sediments, except bauxite.
Some clays, however, such as fireclays, contain very little potash or soda, while they are rich in alumina; and it is a fair inference that hydrated aluminous silicates, such as kaolin, are well represented in these rocks.
There are, in fact, a few clays which contain about 45% of alumina, that is to say, more than in pure kaolin.
These clays are produced by the decomposition of the granite by acid vapours, which are discharged after the igneous rock has solidified ("fumarole or pneumatolytic action").
Many of the clays which pass under this designation belong to the Carboniferous period, and are found underlying seams of coal.
In England, Kimmeridge Clay, Lias clays, London Clay and pulverized shale and slate are all employed for this purpose.
Among the rocks of the continents nothing exactly the same as this remarkable deposit is known to occur, though fine dark clays, with manganese nodules, are found in many localities, accompanied by other rocks which indicate deep-water conditions of deposit.
Similar residual clays sometimes occur on the surface of areas of limestone in hollows and fissures formed by weathering.
Laminated clays of this sort are generally known as shales; they occur in many formations but are very common in the Carboniferous.
As clays they must be sufficiently plastic to be readily moulded, but at the same time possess sufficient stiffness not to contract too strongly in drying, whereby the objects produced would be liable to be warped or cracked before firing.
The principal French fireclays are derived from the Tertiary strata in the south, and more nearly resemble porcelain clays than those of the Coal Measures.
Well-drained soils occur on the sandy and gravely material but more waterlogged soils are found on river alluvium and glacial clays.
Current Work I use stoneware clays of all kinds, ranging from porcelain to crank.
Edinbane Pottery make up their own clay body, blending very plastic clays from Dorset, china clay from Cornwall and potash feldspar.
The book vividly describes the geology of Essex from the deeply buried Paleozoic rocks to the soft sands and clays of the Ice Age.
In the first simulated grouse shoot of its kind, guests shot clays from a line of eight stone grouse butts.
They can consist of clays, muds, sands or gravels or a mixture of these, often cemented together by iron oxides.
The eastern part has no chalk capping and is subject to frequent mudslides in the waterlogged soft limestones and clays.
These clays contain round nodules of limestone with ammonites preserved in green calcite crystal tho there are very difficult to clean.
However, the ability of some soil clays to fix or release potash complicates the picture.
Although these clays were fine, they were also limited and could not have been used for large-scale pottery production.
Soils and clays will tend to hold ground water, so will have a lower resistivity than rock or stone.
These gravels are more resistant to scour and can maintain higher slope angles than the estuarine silts and clays.
The sandstone plateau around the hills gives rise to red, silty, loam soils over silty, loam soils over silty clays.
There are many interesting and unique things for sale in the shop, from fairy houses sculpted using various clays to handmade decorated stoneware.
Heavy clays, gravel and sands, containing cypress stumps, driftwood and mastodon bones, are characteristic. The loess or bluff formation lies along the bluffs bordering the Bottom, nearly continuously through the state.
Where there is complete freedom from stagnant water in the ground, and abundant room for the spread of its branches to light and air, the larch will flourish in a great variety of soils, stiff clays, wet or mossy peat, and moist alluvium being the chief exceptions; in its native localities it seems partial to the debris of primitive and metamorphic rocks, but is occasionally found growing luxuriantly on calcareous subsoils; in Switzerland it attains the largest size, and forms the best timber, on the northern declivities of the mountains; but in Scotland a southern aspect appears most favourable.
At the same time another branch of the same gulf protruded northwards in the direction of the Aral, probably as far as the Sary Kamish depression, which lies to the west of the Khivan delta of the Oxus, separated from it by wide beds of loess, clays and gravel, covering rocks of an unknown age.
The loess, the re-sorted residual clays, and the glacial clays are all used for the production of brick.
I make a range of ceramics using red earthenware clays.
The sandstone plateau around the hills gives rise to red, silty, loam soils over silty clays.
This skeet vest is made from washable polycotton fabric with fine mesh net back panels to keep you cool and comfortable whilst shooting clays.
Cat litter comes in many varieties from clumping clays or silica to more naturally-derived options such as corn or pine-based products.
Clays and salts for use in beauty products are available in bulk, as are other ingredients like aloe vera gel.
The Naturals Collection is inspired by the earth - not the sun, trees, and sky, but the natural stones and clays of the ground.
In winter it perishes in heavy, rich clays when on the level ground.
Clay, sands, loam and rocky debris are respectively the chosen homes of certain species, and several choose the blackest and stickiest of clays.
Pottery vessel sinks are made by merging a blend of clays, fillers, and fluxes together in a firing process.
An application of white or colored glaze adheres to the exterior and interior surfaces and fuses to the clays body in the same firing method.
Styling products such as waxes and clays will define this look and add texture.
The clays of the Rolling Downs formation overlie a series of sands and drifts, saturated with water under high pressure, which discharges at the surface as a flowing well, when a borehole pierces the impermeable cover.
The oak grows most luxuriantly on deep strong clays, calcareous marl or stiff loam, but will flourish in nearly any deep well-drained soil, excepting peat or loose sand; in marshy or moist places the tree may grow well for a time, but the timber is rarely sound; on hard rocky ground and exposed hillsides.
The Cambrian is represented by blue clays, ungulite sandstones and bituminous slates in Esthonia and St Petersburg.
For days together the traveller sees no other vegetation; even this, however, disappears as he approaches the regions recently left dry by the Caspian, where saline clays, bearing a few Salsolaceae, or mere sand, take the place of the black earth.
Tuscaloosa clays are used in the manufacture of pottery.
Overlying the Tuscaloosa are the Eutaw sands, characterized by sandy laminated clays, and yellow, orange, red and blue sands, containing lignite and fossil resin.
The calcareous Claiborne or ClaiborneLisbon formation-group lies south of the last, in a wedge-like strip with the apex on the Alabama boundary; it is a series of clays and sands, richly fossiliferous.
The Grand Gulf group, of formations of different ages, consisting of sands, sandstones and clays, and showing a few fossil plants, but no marine fossils, extends southward from the last to within a few miles of the coast, and is 750-800 ft.
Its materials are pebbles, clays and sands of various' colours from white to deep red, tinged with peroxide of iron, which sometimes cements the pebbles and sands into compact rocks.
Clays and mineral waters are, however, widely distributed.
In regions where climatic conditions are favourable, cotton grows more or less successfully on almost all kinds of soil; it can be grown on light sandy soils, loams, heavy clays and sandy " bottom " lands with varying success.
The " buckshot clays " of the backlands, which are so stiff that they can scarcely be ploughed until flooded and softened, and are remarkably retentive of moisture, are ideal rice soil; but none of the alluvial lands has an underlying hardpan, and they cannot as a rule be drained sufficiently to make the use of heavy harvesting machinery possible.
Underneath the surface are beds of sand, gravel and clays, the last affording material for the manufacture of brick, tiles and pottery.
Other important products are lignite, gypsum and a variety of valuable stones and clays.
In the preparation of alum from clays or from bauxite, the material is gently calcined, then mixed with sulphuric acid and heated gradually to boiling; it is allowed to stand for some time, the clear solution drawn off and mixed with acid potassium sulphate and allowed to crystallize.
They consist chiefly of sands and clays of aeolian and freshwater origin.
Its upheaval above the great sea which submerged all the north-west of the Indian peninsula long after the Himalaya had massed itself as a formidable mountain chain, belongs to a comparatively recent geologic period, and the same thrust upwards of vast masses of cretaceous limestone has disturbed the overlying recent beds of shale and clays with very similar results to those which have left so marked an impress on the Baluch frontier.
It is found in the form of oxide (silica), either anhydrous or hydrated as quartz, flint, sand, chalcedony, tridymite, opal, &c., but occurs chiefly in the form of silicates of aluminium, magnesium, iron, and the alkali and alkaline earth metals, forming the chief constituent of various clays, soils and rocks.
Some of the stiff boulder clays or " till " so prevalent over parts of the north of England appear to have been deposited from ice sheets during the glacial period.
Generally speaking, soils containing from 30 to 50% of clay and 50 to 60% of sand with an adequate amount of vegetable residues prove the most useful for ordinary farm and garden crops; such blends are known as " loams," those in which clay predominates being termed clay loalns, and those in which the sand predominates sandy roams. " Stiff clays " contain over 50% of clay; " light sands " have less than to %.
In clays whose particles are exceedingly minute the water travels very slowly but may ultimately reach a height of many feet above the level of the " water-table " below.
Typical clay-marls are tenacious, soapy clays of yellowish-red or brownish colour and generally contain less than 50% of lime.
It is best adapted for application to clays and fen lands and should not be practised on shallow light sands or gravelly soils, since the humus so necessary for the fertility of such areas is reduced too much and the soil rendered too porous and liable to suffer from drought.
Chocolate or dove-colored grounds with delicate diapers in gold and engobe; brown or black faience with white, yellow and pink designs incised or in relief; pottery curiously and deftly marbled by combinations of various colored clays these and many other kinds are to be found, all, however, presenting one common feature, namely, skilful finger-moulding and a slight roughening of the surface as though it had received the impression of coarse linen or crape before baking.
They consist of fine clays with nodular calcareous concretions rich in fossils.
Ironstone is found in the Wadhurst Clay, a subdivision of the Hastings beds, clays and calcareous ironstone in the Ashdown sand, but the industry has long been discontinued.
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 Keuper clays yield material for bricks.
The clays used are exclusively American, much being obtained in Missouri.