Porous Sentence Examples

The porous soil absorbs the moisture, and fresh water is scarce.

Porous carbon blocks, made by strongly heating a mixture of powdered charcoal with oil, resin, &c., were introduced about a generation later, and subsequently various preparations of iron (spongy iron, magnetic oxide) found favour.

Thus, while the mineral may be formed in a stratum other than that in which it is found, though in many cases it is indigenous to it, for the formation of a natural reservoir of the fluid (whether liquid or gas) it is necessary that there should be a suitable porous rock to contain it.

The main requisites for a productive oil or gas field are a porous reservoir and an impervious cover.

If, however, no porous division be used to prevent the intermingling by diffusion of the anode and cathode solutions, a complicated set of subsidiary reactions takes place.

The vessel may be a flower-pot sawn in two, so that the halves may be bound together when used, or it may be a flower-pot or box with a side slit which will admit the shoot; this vessel is to be filled compactly with suitable porous earth, the opening at the slit being stopped by pieces of slate or tile.

Slate pots or tubs, usually square, are sometimes adopted, and are durable and otherwise unobjectionable, only, their sides being less porous, the earth does not dry so rapidly, and some modification of treatment as to watering is necessary.

First, if the skeleton which it forms is continuous, then its planes of junction with the metallic matrix offer a path of low resistance to the passage of liquids or gases, or in short they make the metal so porous as to unfit it for objects like the cylinders of hydraulic presses, which ought to be gas-tight and water-tight.

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.

During the rainy season there is a considerable body of water in these channels, but owing partly to rapid evaporation and partly to the porous character of the soil the surface of the country dries rapidly.

Except in the marshy regions and along the rivers, the soil is dry, porous and sandy.

Carbonado or " black diamond," found in Bahia (also recently in Minas Geraes), is a black material with a minutely crystalline structure somewhat porous, opaque, resembling charcoal in appearance, devoid of cleavage, rather harder than diamond, but of less specific gravity; it sometimes displays a rude cubic crystalline form.

In any case, it is evident that the transmission of heat by percolation would be much greater in porous soils and in the upper layers of the earth's crust than in the lower strata or in solid rocks.

It might indeed have been thought that thorough drainage would be unnecessary, but it must be noted that porous subsoils or efficient drains do not act merely by carrying away stagnant water which would otherwise cool the earth, incrust the surface, and retard plant growth.

Porous soils and a large supply of water may have beds of 40 ft.

In this way as the water sinks down through the porous subsoil or into the subterranean drains oxygen enters and supplies an element which is needed, not only for the oxidation of organic matters in the earth, but also for the direct and indirect nutrition of the roots.

It is the chief seat of the manufacture of the porous earthenware water-bottles used all over Egypt.

But where the concrete or mortar is not well made and is porous, the continual passage of water through it will gradually break up and dissolve away the calcareous constituents of the cement until its strength is utterly destroyed.

Bunsen prepared the metal by electrolysing manganese chloride in a porous cell surrounded by a carbon crucible containing hydrochloric acid.

Elm is very liable to warp and shake, is porous and usually cross-grained.

The wood is heavy, strong and hard; white to light reddish-brown in colour; and durable if kept either dry or wet; is porous and works easily; it weighs about 40 to 48 lb per cub.

When the " candles " of carbon monoxide appear, the pasty mass is quickly drawn out of the furnace into iron " bogies," where it solidifies into a grey, porous mass, the " black-ash."

These mechanical furnaces do the work of from four to ten ordinary furnaces according to their size, with comparatively very little expense for labour, but they must be very carefully managed and the black-ash from them is more difficult to lixiviate than that from hand-wrought furnaces, because it is less porous.

There are, however, numerous wells, water being obtained freely from the porous sandstone which underlies a great part of the Libyan desert.

The ancient city walls are in some points still existing, in others they have been much restored; they are built of rectangular blocks of porous limestone about IL ft.

As a rule it makes rather barren land; it is highly porous, and the rain rapidly sinks into it.

If steam or vapour is " wire-drawn " or expanded through a porous plug or throttling aperture without external loss or gain of heat, the total heat (E+pv) remains constant (Thermodynamics, § I I), provided that the experiment is arranged so that the kinetic energy of flow is the same on either side of the throttle.

On a small scale it is obtained by reducing the trioxide in a current of hydrogen, or the chloride by sodium vapour, or the oxide with carbon in the electric furnace; in the last case the product is porous and can be welded like iron.

Ordinary commercial copper is somewhat porous and has a specific gravity ranging from 8.2 to 8.5.

These occluded gases are all liberated when the copper cools, and so give rise to porous castings, unless special precautions are taken.

The soil is thin and porous and does not retain moisture, consequently the long, dry season turns the country into a barren desert, relieved only by vegetation along the river courses and mountain ranges, and by the hardy, widelydistributed carnahuba palm (Copernicia cerifera),which in places forms groves of considerable extent.

It had long been known that under certain conditions large quantities of nitrate (saltpetre) are formed on exposed heaps of manure, &c., and it was supposed that direct oxidation of the ammonia, facilitated by the presence of porous bodies, brought this to pass.

The resulting alloy, which is called the lead button, is then submitted to fusion on a very porous support, made of bone-ash, and called a cupel.

The heat is sufficient to keep the resulting lead oxide fused, and the porous cupel has the property of absorbing melted lead oxide without taking up any of the metallic globule, exactly in the same way that blottingpaper will absorb water whilst it will not touch a globule of mercury.

The steam-chest is not used to such an extent, as the bottom would be prematurely corroded; less water is used, as the pulp would become too thin on account of the soluble salts (sodium chloride, sulphate, &c.) going into solution; and the roasted ore is not ground, as the hot brine readily dissolves the silver chloride from the porous ore, and thus brings it into intimate contact with iron and quicksilver.

In later installations, under the 1895 patent, the anodes are placed horizontally on a porous tray resting within the solution above an endless silver band revolving, also horizontally, over rollers placed near the ends of a long shallow tank.

Borchers uses the alloy, granulated, in an anode chamber separated from the cathode cell by a porous partition through which the current, but not electrolyte, can pass freely.

In the Arroostook valley, however, is the largest undivided area of good arable land in all New England, the soil being a deep, porous, yellow loam well adapted to the growth of cereals and to market gardening.

The filling between the girders and floor beams consists of segmental arches of brick, segmental or flat arches of porous (sawdust) terra-cotta, or hard-burned hollow terra- - cotta voussoirs, or various patented forms of con crete floors containing ties or supports of steel or iron.

Such fire-proof coverings, and also interior partitions, are composed of hollow, hard-burned terra-cotta blocks, of porous (sawdust) terra cotta, or various plastic compositions applied to metallic lath, many of which are patented both as to material and method of application.

The gentle declivity of the surface and the porous character of the prevailing sandstone formation render the drainage excellent.

By lowering the head of water in any well which draws its supply from porous rock, the yield is always temporarily increased.

If the strata were uniformly porous the water would lie in the rock at different depths below the surface according to the previous quantity and distribution of the rainfall.

Subject to the rock being porous this process would be continued until the greater column of the lighter fresh water balanced the smaller head of sea water.

It would conceivably take but a small fraction of the period that has in most cases elapsed since such upheavals occurred for the salt water to be thus displaced by fresh water, and for the condition to be attained as regards saturation with fresh water, in which with few exceptions we now find the porous portions of the earth's crust wherever the rainfall exceeds the evaporation.

In this case, as in that of a level plane of uniformly porous sand, the vertical section of the figure is tangential to the vertical well and to the natural level of the subsoil water.

The importance of this illustration is to be found elsewhere than in islands, or peninsulas, or in uniformly porous sand.

Where the strata are not uniformly porous, they may resist the passage of water from the direction of the sea or they may assist it; and round the whole coast of England, in the Magnesian limestone to the northeast, in the Chalk and Greensand to the east and south, and in the New Red Sandstone to the west, the number of wells which have been abandoned as sources of potable supply, owing to the percolation of sea water, is very great.

Even the beds of sluggish rivers flowing over porous strata generally become so impermeable that excavations made in their neighbourhood, though freely collecting the subsoil water, receive no FIG.

Thus, if dry clay is prevented from expanding, and one side be sub j ected to water pressure while the other side is held up by a completely porous medium, the percolation will be exceedingly small; but if the pressure preventing the expansion is reduced the clay will swell, and the percolation will increase.

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.

Land is not in a satisfactory condition with respect to drainage unless the rain that falls upon it can sink down to the minimum depth required for the healthy development of the roots of crops and thence find vent either through a naturally porous subsoil or by artificial channels.

When the higher-lying portion of such land is porous, rain falling upon it sinks down until it is arrested by clay or other impervious matter, which causes it again to issue at the surface and wet the lower-lying ground.

On account of the small amount of precipitation, the fissured condition of the underlying lava sheets, and the porous soil, the Great Sandy Desert has practically no surface streams even in the wet season, and within its limits no potable waters have been found.

All the chlorine, however, does not appear to be removed by this process, the residue having the composition 82FeOH)3FeC13; but it may be by electrolysing in a porous cell (Tribot and Chretien, Compt.

It occupies a narrow strip of land beside the sea, from which it climbs up the steep heights inland to the citadel of Naryn-kaleh, and is on all sides except towards the east surrounded by walls built of porous limestone.

It has passed into solution, filtered through the porous matrix, and has been again precipitated when the conditions were suitable.

In the upper provinces of India water is made to freeze during cold clear nights by leaving it overnight in porous vessels, or in bottles which are enwrapped in moistened cloth.

This phenomenon seems to arise from rains which, falling on the chalk hills, sink into the porous soil and reappear after a time from crevices at lower levels.

These include our range of porous asphalts using specially modified binders.

For example, high trafficked porous asphalt and stone mastic asphalt.

The high temperatures generated fuse the ore particles and fluxes together to form a porous clinker called sinter.

I am using the modification of the Eshelby approach to model for the elastic constants of porous coatings.

The remaining litharge was absorbed by the porous cupel, leaving a globule of metallic silver about 99.9% pure.

The rest of the litharge was absorbed in the porous cupel, leaving a shining globule of metallic silver about 99.95% pure.

Remember, the old, traditional materials and finishes were textured, rather that highly finished, porous not impervious.

It may also be sprayed over a porous titanium coating where it is used to promote bone ingrowth.

Polycom glass is porous sol-gel glass with its pores filled with poly(methyl methacrylate ).

The reagents used for cleaning will be likely to penetrate the porous body and residual contamination may well be found beyond the first monolayer.

The porous paving can be materials such as gravel, grasscrete, porous (no fines) concrete blocks or porous asphalt.

G4 Pond Sealer A moisture curing single part polyurethane varnish ideal for sealing damp porous surfaces prior to using release agent.

Papers produced from the pulp are highly porous, that is, they allow easy passage of water.

Yes, it is possible to paint on slightly porous objects.

With smuggling revenue exploding, and borders increasingly porous, the Iraqi regime -- if not the Iraqi people -- is doing better economically.

At Great Orme this reaction has been particularly intense, due to the extremely porous nature of the ground.

The research implies the moons are very porous - similar to moons orbiting just outside Saturn's rings.

Andrew Newton Slates are not porous, at least not in the sense you mean.

They're a taste of what happens when the barriers of our personality become porous.

To guard against frost damage they are fired to 1160 degrees centigrade yet remain porous allowing roots to breathe and preventing waterlogging.

The project will combine analytical studies and numerical modeling tools for simulating wave propagation in fractured porous rock.

A common approach is to place a porous biomaterial scaffold, seeded with cells, in a flow perfusion bioreactor.

The fluorescent probe was incorporated into thin films and three dimensional porous scaffolds demonstrating the capabilities of monitoring on-line.

A porous material, marble requires proper periodic resealing with a penetrating sealer to prevent staining.

The indentation effect might even be at work in the way porous silicon (with a myriad of nanoscopic filaments) emits light.

The BHR, with an integral porous surface, eliminates that element of possible adverse synergism between titanium and cobalt-chrome.

As wood is slightly porous a touch of air gets into the wine which helps to soften the tannins as the wine matures.

Details regarding previous work on the processing, properties and characterisation of porous titanium for bio-medical applications can be accessed by clicking here.

In porous ground the basin will need to be made watertight.

Methods of available for continuously feed oil to porous bearing using force feeding or using very simple wick feeds.

Flood waters disappear often within a distance of a few miles, being absorbed by porous soil, stretches of sand, and sometimes by the underlying bed-rocks.

However much compressed by mechanical means it is still a porous mass, and when it is confined as in a gun the flame and hot gases from the portion first ignited permeate the remainder, generally causing it actually to detonate, or to burn so rapidly that its action approaches detonation.

Even then, however, the liquid nature of the substance, though advantageous in one or two directions, constituted a serious obstacle to its safe transport and storage and to its efficient employment; it was therefore not until Nobel produced plastic solid preparations by mixing the liquid with porous substances, such as gunpowder, or carbon and sulphur, and finally kieselguhr in a fine state of division, capable of absorbing and retaining considerable quantities of it, that it could be employed as a blasting agent (see Explosives, Dyna Mite, Cordite).

The eye, for example, is damp and porous, and the act of seeing consists in the reflection of the image (SELKeAov) mirrored on the smooth moist surface of the pupil.

The advantage of this plough over the ordinary form is in the absence of sliding friction, and in the mellow and porous condition in which it leaves the bottom of the furrow.

From these and other considerations it is obvious that (I) the electrolyte must be such as will freely dissolve the metal to be refined; (2) the electrolyte must be able to dissolve the major portion of the anode, otherwise the mass of insoluble matter on the outer layer will prevent access of electrolyte to the core, which will thus escape refining; (3) the electrolyte should, if possible, be incapable of dissolving metals more electro-negative than that to be refined; (4) the proportion of soluble electro-positive impurities must not be excessive, or these substances will accumulate too rapidly in the solution and necessitate its frequent purification; (5) the current density must be so adjusted to the strength of the solution and to other conditions that no relatively electro-positive metal is deposited, and that the cathode deposit is physically suitable for subsequent treatment; (6) the current density should be as high as is consistent with the production of a pure and sound deposit, without undue expense of voltage, so that the operation may be rapid and the "turnover" large; (7) the electrolyte should be as good a conductor of electricity as possible, and should not, ordinarily, be altered chemically by exposure to air; and (8) the use of porous partitions should be avoided, as they increase the resistance and usually require frequent renewal.

The loess soil, chiefly a mixture of porous clay and carbonate of lime, forms the bluffs bordering the bottom lands of the Missouri and is common in the N.E.

The suction may be derived from any form of air-pump; a form often employed where water at fair pressure is available is the jet-pump, which in consequence is known as a filter-pump. Another method of filtering into a vacuum is to immerse a porous jar ("Pukall cell") in the liquid to be filtered, and attach a suction-pipe to its interior.

It seems fairly established that when the preliminary heating process of fermentation is drawing to a close, the cotton, hay, &c., having been converted into a highly porous friable and combustible mass, may then ignite in certain circumstances by the occlusion of oxygen, just as ignition is induced by finely divided metals.

Any cracks were thus, no doubt, temporarily closed; and as the structure of the rest of the dam was porous, no opportunity was given for the percolating water to accumulate in the horizontal fissures to anything like the head in the reservoir.

The brine solidifies to become hydrogel, a highly porous solid substance.

A very important part of the RHS survey stated that it is undesirable to have non- porous materials in gardens such as concrete.

In general, soft, porous or severely weathered stone must be treated with a softer, weaker mortar than hard, dense stone.

Look carefully at the upper portion of the boot and make sure that it is made from a soft material like good quality leather, or a synthetic fabric that is porous and will allow your feet to breathe.

The fabric is very porous, allowing air to easily pass through the cover and mattress.

The chemicals used to remove the residue can damage the surface, especially if it's porous, like wood.

Because they are porous, they require regular seasoning with oil to maintain a non-stick surface.

Unglazed pots have the advantage of holding a lot of moisture because they are porous.

It grows freely in a dry porous soil, and in default of seed may be increased by cuttings taken in early summer; but seed is in every way best.

On a porous bottom it may be plentifully watered during a dry time in summer without fear of injuring the roots.

New Jersey Tea (Ceanothus Americanus) - Though one of the hardiest, this thrives best against a wall, and in a dry porous soil; the flowers, in succession from about the middle of June till August, white.

A well-drained subsoil with a porous surface soil suits them best, and shelter from hard frost and nipping winds is of great service.

This unique, non porous material can be poured, shaped and molded into any shape, complete with integral sinks and backsplashes.

After being heat-cured, the tiles retain their natural color and are porous, which means that they have the ability to absorb water.To make them non-porous, they need to have a sealant or glaze applied to them.

This is probably attributed to the firmer and less porous skin of the fruit.

Others can cause damage to porous materials such as concrete, brick or wood.

Osteoporosis-Literally meaning "porous bones," this condition occurs when bones lose an excessive amount of their protein and mineral content, particularly calcium.

These chemicals cause blood vessels to become more porous, allowing fluid to accumulate in tissue and leading to the swollen and reddish appearance of hives.

The mass of bone increases, but the new bone material that is added is porous, weak, and brittle.

Cancellous bone, whose porous structure with small cavities resembles sponge, predominates in the pelvis and the 33 vertebrae from the neck to the tailbone.

Unfortunately, since human hair wigs feature porous strands, these wigs can absorb odors and need to be washed frequently in order to maintain their bounce and fresh quality.

Even in this case, dark porous hair types will endure severe cuticle damage during the coloring process.

Keep in mind that permed or chemically processed hair is more porous than untreated hair types and, therefore, color may not be absorbed evenly.

Any porous surface can harbor lice and their eggs.

The skin was isolated from the blades by a micro porous screen.

Reed may look like a wood, but it is actually a special porous fiber that will slowly absorb and release your fragrance.

They may be large, but they are very porous (unlike the crystalline diamond structure used for jewelry).

Untreated or naked leathers are porous; avoid contact with oils, water, or other substances that will result in staining.

Using porous materials such as plastic or acrylic in a piercing, even a healed piercing, can cause bacteria to breed in the pores of the jewelry.

If you are wearing a porous material such as acrylic or plastic, bring appropriate jewelry made out of glass, stainless steel, titanium, niobium or PTFE to your doctor's appointment.

These materials can be run through an autoclave sterilizer and are not porous, which means that they do not harbor bacteria and can be worn in a fresh piercing or for extended periods of time.

It cannot be put into an autoclave sterilizer without melting, and it is extremely porous.

Red meat is porous and hard to saturate without altering the consistency and flavor.

You may have chosen granite because of its hardness and durability, but this material is more porous than marble.

Remember that with vegetables, a more porous interior means that it has more water content, which is what you need when you're trying to burn fat.

This is especially problematic for softer, porous produce.

Vinyl isn't very porous, though, so it will be easy to handle it on your own with just the soap and water.

Moreover, one of the most attractive features of silk is that it adjusts to body temperature, warming its wearer during colder nights and also remaining porous and airy in warmer climates.

The electromotive force of each cell is i 07 volts and the resistance 3 ohms. The Fuller bichromate battery consists of an outer jar containing a solution of bichromate of potash and sulphuric acid, in which a plate of hard carbon is immersed; in the jar there is also a porous pot containing dilute sulphuric acid and a small quantity (2 oz.) of mercury, in which stands a stout zinc rod.

Plates of platinum and pure or amalgamated zinc are separated by a porous pot, and each surrounded by some of the same solution of a salt of a metal more oxidizable than zinc, such as potassium.

The liquid when soaked into a porous combustible substance like blotting-paper burns rapidly and quietly, and when struck with a hammer on a hard surface violently detonates; when a little of the liquid is spread on an anvil and struck, the portion immediately under the hammer only will, as a rule, detonate, the remainder being scattered.

There is an abundant rainfall, but owing to the porous nature of the soil the water percolates into deep caves which have communication with the sea, and becomes brackish.

Lord Kelvin's experiment with a current of gas forced through a porous plug is also given.

The loess soil, chiefly a mixture of porous clay and carbonate of lime, forms the bluffs that border the bottom lands of the Missouri.

For pot culture, the soil should consist of three parts turfy loam to one of leaf-mould and thoroughly rotted manure, adding enough pure grit to keep the compost porous.

The anhydrous salt is a colourless powder or porous mass, having an alkaline taste and reaction.

Charcoal is a porous form of carbon; several varieties exist.

In the wet season the rain is quickly absorbed by the dry, porous soil; consequently there are no rivers and no lakes except near the forested region of the south-east.

The product obtained after burning is known either as kelp or varec. Another method of obtaining kelp is to heat the seaweed in large retorts, whereby tarry and ammoniacal liquors pass over and a very porous residue of kelp remains.

It was found, for instance, that a film of insoluble copper ferrocyanide, deposited in the walls of a porous vessel by the inward diffusion and meeting of solutions of copper sulphate and potassium ferrocyanide, would allow water to pass, but retained sugar dissolved in that liquid.

Certain districts, indeed, in which a layer of heavy loam underlies the porous and friable surface, are able to retain the moisture which elsewhere is absorbed.

On the other hand, if the concrete is rough and porous the sea-water will gradually eat into the heart of the structure, especially in a case like a dam, where the water, being higher on one side than the other, constantly forces its way through the rough material, and decomposes the Portland cement it contains.

The reason for this preference lies in the fact that being porous and full of air, they are a good non-conductor.

But they are weak, and modern experience goes to show that a strong concrete is the best, and that probably materials like broken clamp bricks or burnt clay, which are porous and yet strong, are far better than cinders as a fireproof aggregate.

These are unfitted for garden purposes until improved by draining, liming, trenching and the addition of porous materials, such as ashes, burnt ballast or sand, but when thoroughly improved they are very fertile and less liable to become exhausted than most other soils.

The water which drains from the plants or is spilt in watering would fall on the bottom, which should be made porous to carry it away.

When employed for making vine borders, loam of a somewhat heavier nature can be used with advantage, on account of the porous materials which should accompany it.

In other cases they are planted in open baskets of wood or wire, using the porous peat and sphagnum compost.

When it is considered that a parting of the clay, sufficient to allow the thinnest film of water to pass, may start the formation of a vein of porous sand in the manner above explained, it will be readily seen how great must be the attention to details, in unpleasant places below ground, and below the water level of the surrounding area, if safety is to be secured.

Theca porous; septa compact and reduced in number.

Also I made pores for porous plasters and high-grade holes for doughnuts and buttons.

In the experiment imagined by Lord Rayleigh a porous diaphragm takes the place of the partition and trap-doors imagined by Clerk Maxwell, and the molecules sort themselves automatically on account of the difference in their average velocities for the two gases.

The rains are quickly absorbed by the light porous soil and leave only temporary effects on the surface, where arboreal growth is stunted and grasses are commonly thin and harsh.

Such a rock is typically exemplified by a coarse-grained sandstone or conglomerate, while a limestone may be naturally porous, or, like the Trenton limestone of Ohio and Indiana, rendered so by its conversion into dolomite and the consequent production of cavities due to shrinkage - a change occurring only in the purer limestones.

Water, often saline or sulphurous, is also found in these porous rocks and replaces the oil as the latter is withdrawn.

As an example of a fairly constant cell we may take that of Daniell, which consists of the electrical arrangement - zinc zinc sulphate solution copper sulphate solution copper, - the two solutions being usually separated by a pot of porous earthenware.

Thus as long as a moderate current flows, the only variation in the cell is the appearance of zinc sulphate in the liquid on the copper side of the porous wall.

A deep porous bed in the upper layers is essential, and this should consist of fine particles which lie close to each other without any tendency to stick together and " puddle " after heavy showers.

The addition of small quantities of lime, especially in a caustic form, to stiff greasy clays makes them much more porous and pliable.

When an alkaline chloride, say sodium chloride, is electrolysed with one electrode immersed in a porous cell, while caustic soda is formed at the cathode, chlorine is deposited at the anode.

A continuous stream of gas, supplied at a constant pressure and temperature, is forced through a porous plug, from which it issues at a lower pressure through an orifice carefully surrounded with non-conducting material, where its temperature is measured.

Any air bubbles are removed from the surface of the body by brushing with a camel-hair brush; if the solid be of a porous nature it is desirable to boil it for some time in water, thus expelling the air from its interstices.

Another important point, in which the moas agree with the other Ratitae and differ from the kiwis, are the branched, instead of simple, porous canals in the eggshell.

The residual gas is then passed through a tube containing porous materials, such as woodor bone-charcoal, platinized pumice or spongy platinum, then mixed with steam and again forced through the tube.

Each cell contains a zinc plate, immersed in a solution of zinc sulphate, and also a porous chamber containing crystals of copper sulphate and a copper plate.

When heated to nearly a red heat it gives a porous friable mass which is known as "burnt alum."

The outcrop of a metalliferous vein frequently manifests itself as a line of rocks stained with oxide of iron, often honeycombed and porous, the " gossan " or " eisen-hut," the iron oxide of which results from the decomposition of the pyrites, usually present as a constituent of such veins.

In the first place, soil, to be of any use, must be sufficiently loose and porous to allow the roots of plants to grow and extend freely.

Following in the furrow of an ordinary plough it breaks through the sub-soil to a depth of several inches, making it porous and penetrable by plant roots.

In the limiting case of a long fine tube, the bore of which varies in such a manner that U is constant, the state of the substance along a line of flow may be represented by the line of constant total heat, d(E+pv) = o; but in the case of a porous plug or small throttling aperture, the steps of the process cannot be followed, though the final state is the same.

Though, thanks to the overlaying porous pumice, the Taupo plateau is not fertile, it has a good rainfall and is drained by unfailing rivers running through deep terraced ravines.

Similarly it is necessary, in view of the hydrostatical relations of water and mineral oils, and the volatile character of the latter, that the porous stratum should be protected from water and air by an overlying shale or other impervious deposit.

The material used is a soft, porous magnesian limestone, which is well adapted to the purpose in view.

Constant cells may be divided into two groups, according as their action is chemical (as in the bichromate cell, where the hydrogen is converted into water by an oxidizing agent placed in a porous pot round the carbon plate) or electrochemical (as in Daniell's cell, where a copper plate is surrounded by a solution of copper sulphate, and the hydrogen, instead of being liberated, replaces copper, which is deposited on the plate from the solution).

Generally it is either dried, after being separated from the wash water, by means of common salt, upon a layer of which the moist nitroglycerin is gently run and allowed to drain or filter through, or it is filtered through a mass of dry sponge or similar dry and porous material.

Tantalum tetroxide, Ta 2 0 4, is a porous dark grey mass harder than glass, and is obtained by reducing the pentoxide with magnesium.

This difficulty was overcome by first filling the cylinder with porous briquettes and then soaking them with a fixed percentage of acetone, so that after allowing for the space taken up by the bricks the quantity of acetone soaked into the brick will absorb ten times the normal volume of the cylinder in acetylene for every atmosphere of pressure to which the gas is subjected, whilst all danger of explosion is eliminated.

The introduction of acetylene dissolved under pressure in acetone contained in cylinders filled with porous material drew attention again to this use of the gas, and by using a special construction of blowpipe an oxy-acetylene flame is produced, which is far hotter than the oxy-hydrogen flame, and at the same time is so reducing in its character that it can be used for the direct autogenous welding of steel and many minor metallurgical processes.

The whole is surrounded by a deep and wide ditch, which can be filled from the river, at the risk, however, of bringing down the whole structure, for the walls are of mud, and stand upon a porous sandy soil.

All are built in the Doric style, of the local porous stone, which is of a warm red brown colour, full of fossil shells and easily corroded when exposed to the air.

In some cases porous diaphragms have been employed; but such diaphragms introduce a new complication, for the liquid as a whole is pushed through them by the action of the current, the phenomenon being known as electric endosmose.

Common throughout the northern and middle states and Canada, the red oak attains a large size only on good soils; the wood is of little value, being coarse and porous, but it is largely used for cask-staves; the bark is a valuable tanning material.

It had been found by experience that the charta Augusta was, from its fineness and porous nature, ill suited for literary use; it was accordingly reserved for correspondence only, and for other purposes was replaced by the new paper.

The ratio of cases to population living in Dublin on loose porous gravel soil for the ten years1881-1891was I in 94, while that of those living on stiff clay soil was but 1 in 145.

Zinc dissolves at the anode, an equal amount of zinc replaces an equivalent amount of copper on the other side of the porous partition, and the same amount of copper is deposited on the cathode.

In order to make spongy or porous rubber, some material is incorporated which will give off gas or vapour at the vulcanizing temperature, - such as carbonate of ammonia, crystallized alum, and finely ground damp sawdust.

Its depth, together with its porous nature, makes the fertile soil of Iowa capable of withstanding the extremes of wet and dry remarkably well, and it is perhaps true that, taken as a whole, no other state in the Union has a superior soil for agriculture.