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D, the lower part of the fire-box, containing the fire u, u, the iron rails, supported on the railway by cast-iron grate.

chairs fixed on wooden girders. B, the pipe through which the steam escapes after it has V, the frame of the stuffing-box of the cylinders. acted on the pistons.

x, x, the cylindric generator, covered with a wooden jacket F, the cast-iron cylinder in which the piston moves, there to prevent the radiation of heat from the metal. The level of being one on each side of the engine. An aperture is repre- the water in the generator rises nearly to the tube A, and in sented as made in the cylinder in order to show the the middle of the water are copper tubes a, through which piston.

the products of combustion pass in order to heat it, and escape G, the rod employed to open the valve i, in order to admit into the smoke-box. the steam into the pipe a. "In the figure, the engine-man y, the smoke-box, in which the tubes a, terminate. holds in his hand the lever which puts this rod in motion. z, z, the fire-box, surmounted by a dome in which the steam

H, the stop-cock, for emptying and cleaning out the is produced. generator.

à, copper-tubes to the number of 125, open at both ends, and 1, the valve, which is opened and shut by the hand, in terminating in the fire-box and the smoke-box. Through order to regulate the supply of steam.

these tubes the heat of the fire is communicated to the water K, the great double-armed or forked connecting-rod, which in the generator, and by it converted into steam. connects the head of the piston-rod with the crank m, of the b, the sector-guide, placed on the side of the fire-box, and great wheel.

notched so as to be worked by the lever B. The extreme 1, the lamp and reflector, which indicate the approach of the notoh in front corresponds to the forward motion: the extreme engine at night.

notch behind, to the backward motion; the middle notch, to m, the crank, which transmits the motion of the piston to the full stop. The intermediate notches to moderation of the the axle of the great wheel.

motion forwards or backwards. N, the catch, which connects the tender with the engine. e, the cases containing the spiral springs, which regulate the

o, the fire-door, through which the fireman or stoker intro action of the safety-valves i. duces the fuel.

i, the safety-valves. P, the metallic piston, of which the rod is jointed to the con m, m, the steps for ascending the platform of the engine. necting-rod K.

n, the glass-cube placed before the fireman, to indicate the Q, the chimney pipe, for the escape of the smoke, and the level of the water in the generator, with which it communicates steam which has acted on the pistons.

at both ends. R, R, the feed-pipes, which supply the generator with water 7, r, guides intended to keep the motion of the piston in a by means of two force-pumps, not seen in the figure.

straight line. s, the apparatus for clearing the railway of any obstructions. t, i, the stop-cocks for cleaning the cylinder. T, T, the springs which support the generator.

v, the rod which transmits the motion to the stop-cocks, b, t.

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arranged, with boiler-house, near the porth-west corner of the building. The

machines.

engines, both for the purposes of manufacture and locomotions were termia i alderecelinear the sonorine piston-Tod is converted into the curviliorating

In the Great Exhibítion at London, In 1851, 4 vast variety of steam- ; cylinders; to the former, those in which the cylinder is fixed, and lineariosto bited: these belonged principally to the high-pressure class, and motion

of the crank, with shafting attached to it, through the medium of vibrating Felt under the teoring en hese pipes derived chien pieapply to toned swetbolteir; one billed in seven, de repentecoflon-spinning, Weaving, and various other system of clothing the pipes with thick hair-felt, and putting over that a casing of painted canvas, rendered it possible to carry high-pressure steam

Rotary steam-engines of different kinds were also exhibited : in most of to a distance before thought to be impracticable. The pipes were supplied

without the intervention of the crank, and power was led off by bands from

these the curvilinear motion necessary for driving machinery was obtained ilhe condensation of the steam beascaliente e vanta crom where the resultante din present times more lingular de la pompa mothes for sale. There were the marinene percepuble increase or temperatured vaesoe perfecte edo eo complete the phones sobre mean mereka treneris interesting part of the Exhibitionier Themen open tooring. The beam-enginesores formes perto de desen me tyrgenerating appones formed ar ze hemel ponter stora piting the screw-popeller, Broncong To the latter class belong the steam-engines with bracing vasculaires becomes Cer med antenatal korito, tam re application of the steabenõiso.

Since commánication of power is made for the more profitant en terecht ik wees water for medited by rkebele ili oberta i od Pevolution affected by proveniente mo

stone, alternating with slaty clay. All the sands are siliceous or LESSONS IN GEOLOGY.No. LIII.

Ainty, and in colour are brownish or red, and sometimes yel

lowish. The sandstone is, in some places, a coarse conglome. By Thos. W. JENKYN, D.D., F.R.G.S., F.G.S., &c.

rate of pebbles. The fossil wood, the lignites, and the seams

of coaly matter, that are seen in these sands, have misled some CHAPTER V.

into the expectation of finding coal, as at Bexhill, in Surrey. THE CLASSIFICATION OF ROCKS.

III. THE PURBECK BEDS.
SECTION TI.

Purbeck is a small peninsula, on the Dorsetshire coast, near
THE WEALDEN STRATA.

Swanage, where there are fine sections of this group of the

Wealden beds. In the south-east of Eugland there is a considerable district The Purbeck beds consist of slaty marls and of variegated called the Weald of Kent, and the Weald of Sussex, and limestone. What is called Purbeck marble consists chiefly of hence, the peculiar rocks which prevail in those regions have shells, some of them whole, but most of them much worn and been called the WEALDEN.

comminuted. The shells are imbedded in a calcareous cement, The position of the Wealden strata is one of the most which is sometimes very fine and crystalline, and sometimes remarkable phenomena in the science of geology. They lie has only the consistency of hard mari. As a marble it very render the cretaceous beds, which were formed in a deep ocean, much resembles the Petworth or Sussex marble. and they rest upon other rocks, the oolite, which were also Professor Edward Forbes divides the Purbeck beds into formed in the sea; and yet all the beds of the Wealden have three groups, each marked by a peculiar species of organic been formed by river water, and abound in fresh-water shells remains, all of which are different from those found in the and fresh-water animals, with some indications of beds formed higher Wealdens of the Hastings sand and the Weald clay. in brackish and sea-water.

The Purbecks are divided into the upper, the middle, and the

lower beds. I. THE LITHOLOGICAL CHARACTER OF THE The upper consists of purely fresh water beds of about fifty WEALDEN.

feet thick, The Wealden rocks have been generally divided into three

The middle consists of alternations of fresh water and brackish groups, which succeed in the descending order thus :

water and marine deposits, which, for distinction's sake, we 1. Weald clay, with thin beds of sand and shelly limestone.

will enumerate, seriatim, in the descending order :2. Hastings sand, with clays and limy grits.

1. Fresh-water limestone. 3. Purbeck beds, containing different kinds of limestones and 2. A limestone of brackish water full of Cyrena, and tramaris.

versed by beds abounding in Corbule, Melanie, etc.-shells of 1, THE WEALD CLAY.

brackish water. The Weald clay is stiff in texture, dark brown on the sur- and other shells belonging to the sea.

3. A purely marine deposit, with Pecten, Modiola, Avicula, face, but blue beneath, and contains concretional iron-stone. It is finely exposed in the southern cliffs of the Isle of Wight, water and partly in fresh water, in which many fish, and a

4. Beds of limestone and shale, formed partly in brackish in the form of slaty clay and limestone. When the slaty clay reptile called Macrorhyncus, are found. is divided by a knife into laminæ, its surface is found coated with the shells of small cowries called Cypris Faba. The iron: thick, full of the shells of Ostrea distorta, with an Echinoderm,

5. A conspicuous bed called the “ Cinder bed," twelve feet stone of these beds was once extensively worked in the Wealds the first found in the Purbecks. of Sussex and Kent, where the slags or cinders from the ancient 6. Fresh-water linestones filled with species of Cypris, furnaces are still frequently met with. Underneath this clay there are alternations of sands and Paludina, Planorbis

, Cyclas, etc.; all different from any seen in

the beds above. clays, which include a bed of limestone called Sussex marble

7. Thick siliceous beds of chert, filled with the above and Petworth marble, full of the shells of the Paludina vivi

fossils. para.

8. A very thin band of greenish shales, with marine shells, This clay bed surrounds nearly the whole of the Weald forming the base of the middle Purbecks, formation. It was the moistening and the wearing a way of this bed of clay in the Isle of Wight, that occasioned the This distinct enumeration is important, as it shows to you remarkable landslip which took place near Black Gang, in how the land, during the formation of the middle Purbecks, 1799. The thickness of this bed is, in Sussex, from 150 to 200 / was sometimes subsiding and sometimes being elevated. feet, but in the Weald of Kent it is 300 feet.

The lower has a series of beds like the middle group :

1. A purely fresh-water marl, with species of Cypris, ValII. THE HLASTINGS SAND.

vata, etc., different from those of the middle group. It is The Hastings sand is sometimes called " Tilgate Grit,” and about eighty feet thick. the "Iron sand of Tilgate Forest,” because it occupies an ex

2. Brackish water beds, seen at Meups Bay, with a species tensive district of that name.

of Serpula, with Cypris, etc. The shales which contain the Dr. Fitton has divided this group into eight beds :

Cypris are much contorted and broken up.

3. The great Dirt Bed, containing the roots and stumps of 1. Ferruginous and fawn-coloured sands and sandstones,

trees that grew upon the spot. containing small portions of lignite and a stiff grey loam. 4. A fresh-water limestone, a bed about eight feet thick, 2. Sandstone.

containing shells of the same species as those enumerated in 3. A sandstone with concretionary courses of calciferous or bed No. 1 of this lower division. This forms the first sedihe white sandstone, finely exposed in what is called the ments that were deposited by the Wealden river upon the

6. Beds of clay and slate, and thin sandstones, containing The most remarkable bed in the whole of this Purbeck lignites and silicified wood.

series is the Dirt Bed, No. 3, of which you will form some ?. A sandstone without any concretions, but with numerous idea from the annexed wood-cut. veins of argillaceous or clayey iron-stone.

The dirt bed is an accumulation of vegetable mould in 8. Dark-coloured slate, with roundish masses of sandstone, which grew luxurious plants and trees; for in it, and growing and thin layers of lignites, and fragments of wood turned into from it, are found numerous trunks of cycadeous plants ană The Hastings beds are, as a mass, principally arenaceous or growing in their native forests, with their roots in the vegete the Ashburabam beds, are composed of an argillaceous lime- Some of the trunks lie prostrate, but the greater part are up:

limy grit.

coal.

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right, growing a few feet apart, about three or four feet high, reptiles take various names, according to some peculiarity ła
and about two feet in diameter,

their structure,—such as the Streptospondylus, from otpenTOS,

streptos, turned or reversed, and otodòvlos, a vertebra of the Fig. 4. A Quarry in the Isle of Portland,

back or spine the animal with a reversed spine ; Megalosaurus, from payas, megas, usyaan, fem. megalé, fem., and gavpos, lizard=a great or gigantic lizard ; Iguanodon, from Igrana, a reptile in the West Indies, and oãous, odous, a tooth=-having teeth like the Iguana; and Hylæsaurus, from valos, wood, wold, or weald, and savpos, a reptileza lizard found in the wealds of Kent and Sussex, or, the Wealden lizard. As all these reptiles are, in fact, animals of the epochs of the oolite and the lias, they will be more fully described when we treat of these formations.

The Wealden of the Tilgate Forest have supplied numerous fragments of fossil bones, which, from their very slender structure, have been supposed to belong to some animal of a higher order than that of reptiles. They seem to belong to some animal that could fly in the air. It seems, at any rate, to have been an animal that was a link of connection between reptiles and birds, and might be called the Wealden BAT. “It

is,” says Professor ANSTE), "perhaps the most extraordinary
, Fresh-water Limestone ; , Laminated cream-coloured of all the beings, of whose former existence the study of fossils
Limestone; c, the Dirt Bed, with fossil trees penetrating the has made us aware, and is that which, if living, would appear
rock B; D, the lowest Fresh-water Beds of the Purbecks; most unlike any thing that exists in the known world.
E, the Portland Oolite, on which the whole Wealden series was about the size of a snipe, the mouth was formed some-
rests,

thing like that of a crocodile, especially the lower jaw, the

neck was long and like that of a bird, and the feet were II, THE ORGANIC REMAINS OF THE WEALDEN. adapted for water to assist the animal to swim. It could

You have already seen that the upper series of the Wealden, walk, swim, or fly. Its extremities, or what may be called such as the clays and the grits, are marked for their fossils, hands and feet, have fingers, but the finger that is in the the laminæ of the clay being coated with the shells of the place of our little finger has five joints, and each joint very Cypris Faba : and the Petworth or Sussex marble, consisting long, till the centre finger is longer than the animal's body and chiefly of the shells of Paludina Vivipara. These beds, 3 neck. To this finger, to the rest of the arm, to the body, and developed about Brook Point in the Isle of Wight, have sup- to a portion of the hinder leg, a membrareous wing is attached plied a large amount of the bones of enormous reptiles, fresh. --but still so constructed as to allow the animal the free use water shells, river mussels, ferns, and plants, but especially of its arms and legs, even when the wings were not in use. On fossil trees, which are imbedded in sandstone, and protrude account of of its fingers and wings, the animal is called Pterofrom the water-worn surface of the rocks, as seen at low water. dactyl, from repov, pteron, a wing, and dartvlos, daktylos, The trees appear to have been engulphed while in vigorous a finger-a finger-winged, or wing-fingered animal, growth, with their veseels and bark full of sap.

The Purbeck marble is made of small river-snail shells, III. GEOLOGICAL PHENOMENON INDICATED BY
intermixed with the cases of minute cowries or cyprides. To

THE WEALDEN,
geologists, however, the dirt bed in the Purbeck series is far
more interesting than the marble. The fossil plants found in

There is no process that will so effectually imbue your
this bed refer to those now called Cycas and Zamia, plants mind with the principles of geology, as an effort of your own
which betoken a very warm climate. The trees are completely mind to realise the sequence of the mighty changes which
silicificà, and seem to be of the species called araucaria or have taken place in some of the primeval epochs of the earth's
pine.

history. The lithological character of rocks, and the organic
The layers of the calciferous grit of Tilgate Forest seem to remains of different beds, can only supply you with facts, it is
consist of the detritus of plants ground to pieces by being your own mind that must form the logic of the events. You
rolled or agitated in water loaded with sand, especially of the must, therefore, try this deductive process on the Wealden
remains of two species of ferns called Sphenopteris and Lonchop- phenomena which have been related to you.
teris.

1. It seems that, at a period thousands of years or myriads
The prevalent shells of the Wealden have already been of centuries ago, the oolite beds formed the surface of a large
pointed out in our description of the lithological character of district in the northern hemisphere of the globe, having a
the clays and the marbles, some fresh-water, some brackish, climate so warm as to nourish coniferous trees and arborescent
and some marine.

plants and fern, like those found in the dirt bed of the Purbeck
The Wealden fishes are, for the most part, either of the beds. The coast of that district was washed by an ocean
shark family and related genera, or of a species allied to river inhabited by turtles and marine lizards.
pikes. Complete skeletons of fishes are very rare, but detached 2. In the course of ages, that district began to sink, but 60
scales, teeth, and bones abound.

quietly and gradually as to allow the trees to maintain their
What has given the greatest fame to the Wealden is its erect position, and the plants and the vegetable mould to
reptiles. The bones and plates of turtles are very common, remain.
both in the grits of the Tilgate Forest, and in the Purbeck 3. Upon this a mighty river, like the Ganges or the Missis.
limstone-some of these turtles or chelonians being fresl.. sippi, poured its turbid waters so as to cover the district and
water, and others of a marine tribe.

its forests. This river deposited, over the soil and around the Some of the reptiles, whose remains have been discovered trees, a calcareous mud, which gradually became solid limein quarries about Tilgate and Horsham, are evidenty marine stone. This river formed a delta in what is now called the : inii abitants of the sea into which the mighty river of the valley of the Weald in Kent and Sussex, and is lying between Wealden carried down its sand and mud. Such are the the North Downs and the South Downs. The whole of this Plesiosaurus and Cetiosaurus, reptiles of the lias and polite valley, except where it opens to the sea at Hastings, is a denuepoche, but whose species lived to visit the estuaries of the dation of the chalk which once covered the whole of the Wealden stream.

Wealden formation.
Others of the Wealden reptiles were allied to the alligator, 4. The land continued to sink, and the waters of the mighty
the crocodile, and the gavial, being the largest of existing river overwhelmed the forest that had been petrified by ther-
quadrupeds that propagate their species by eggs, and hence mal springs holding Aint in solution, and went on heaping
called oviparous. Still, the fossil forms differed much in upon the surface vast accumulations of detritus brought down
tructure from the present race of crocodiles. These fossil from a distant region,

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6. The country traversed by this river and its tributaries cularly called upon to unite in erecting a suitable monument was of a tropical climate, luxuriating in plants and arborescent to his memory. ferns, and its waters abounded in turtles, and were frequented Dr. Thomson, in seconding the above resolution, said : by gigantic reptiles. The remains of these plants and animals Every one was aware of the merits of Mr. Watt. He himself were brought down by the waters and deposited in the mud had the honour of his acquaintance for twenty-five years. of the deita.

Never before or since that period had he seen or heard of any 6. The next stupendous change was that the entire region, person that was better acquainted with every topic, and had inhabited by these terrible lizards, perhaps a land now under such a general knowledge and understanding. Many attempts the Atlantic, was itself swept away, and the delta continued to had been made to improve Mr. Watt's engine, but the one subside to a great depth, till it was covered by a deep sea inade by himself was the best extant. All the new engines which deposited all over it the sediments of the chalk forma- that are now erecting in Cornwall are upon his plan. The tion.

learned professor concluded by saying, that the steam-engine 7. In this submerged state it lay for a periud incalculably was not only the greatest but the completest present ever long, till, by volcanic action from below, large areas of the made by science to the arts; and that the inventor had contri. district began to upheave, and continued to rise until the buted more to the prosperity and aggranuisement of Great chalk covering became exposed to the action of the waves, so Britain than any man that ever existed. as to-thin it. This rendered it more incapable to resist. The Mr. HouLDSWORTH said: No individual present more appresubterranean power continued to press upward against the ciated the memory of that illustrious gentleman, Mr. Watt, overaying strata until the chalk formation snapped asunder, than he did. Some gentlemen present, who have so great which made it more easy for the waves to carry on the work powers of oratory, could speak from morning to night of his uf denudation, and expose the underlying Wealdens, some merits and his surpassing knowledge, and not exhaust the thing as represented in the next diagram.

subject. Upon these grounds he would leave the case in Fig. 5. Eleration of the Wealden,

abler hands. He concluded by moving the following resolution, which was seconded by Professor Jardine :

IV. “That the gentlemen which he named be appointed a committee for the purpose of procuring subscriptions, with power to form themselves into sub-committees, and to add to Their number when they think proper,"

Dr. Ure, on being called on by the Lord Provost, spoke as follows :--Every citizen of Glasgow should feel grateful to the gentlemen at whose call this publio meeting has been con

vened. The zeal and intelligence now displayed, will, I have A, the North Downs of Surrey. B, the South Downs of no doubt, remove a cause of reproach from this city. London, Sussex.

0, the anticlinal axis of the Wealden near Balcombe. Edinburgh, Greenock, besides several other towns of much D, the Tertiaries of London. E, the Tertiaries of Hampshire.

less note than our own, have already paid their public tribute

of admiration to the genius of Watt. But Glasgow alone, the 8. The abundance of carbonized plants in the Wealden shales scene of the greatest triumph ever achieved by mind over and clays, and the frequent occurrence of lignite, or brown matter, because it was the place where that philosopher's coal

, both in masses and in layers, make these beds look in mind was formed, and his inventive talents developed-Glassome districts as if they belonged to the coal measures. has misled some to open mines for coal, but all in vain. Yet, ombos remained silent, seeming to verify the wise saying,

"A prophet is not without honour, save in his own country." though ihc Eng.ien Wealdens contain no coal, the Wealdens of The merits of Mr. Watt have been recently celebrated by Hanover, in Germany, contain a valuable and extensive coal. statesmen, philosophers, and orators, of the first respectability

in the kingdom; but so transcendent are these meriis, that no praise hitherto bestowed can be called panegyric.' In him were conjoined qualities deemed hardly compatible, and rarely

associated in the same individual. The most lively fancy, BIOGRAPHY.--No. XIV,

which could multiply at will mechanical combinations, or JAMES WATT, INVENTOR OF THE STEAM-ENGINE. expatiate in the fields of romantic literature, was combined (Continued from page 203.)

with the severest judgment, and an unwearied assiduity and

unity of action in accomplishing his ends. The utmost ardour It was contemplating such an object-looking to a monument of friendship was blended with dispassionate considerations on for James Watt, not only as a memorial of the past, but an the true interest of his friends. But the main scope of his rement to the future-not only as an expression of grati- mind, the great business of his life, was the investigation of tude from the present generation, but as a stimulus to genius the laws of nature, with the view of directing her powers to the still unborn-that he anticipated the happiest effects, and that uses of society. And in this respect justice has not been ren. the passing spectator, when he cast his eye upon it, would dered to his fame, owing to an early and unintentional mistake exclaim, Glasgow expects every man to do his duty

of his friend, Professor Robison, which remained uncorrected Mr. WILLIAM Surtu then rose, and said he had the honour in public, from the modesty of Mr. Watt. Professor Robison, of submitting a motion to the meeting, which could require no in his writings, represents Mr. Watt as deriving his knowledge argument of his to recommend it to their notice, not only be- of the constitution of steam, and consequently of the first of the resolutions to which they had already agreed; but also whose

lectures he is described as attending, at the period of cause it appeared to follow almost as the necessary consequence principles of his steam-engine, from the lessons of Dr. Black, because so much had already been said, and so well said, on making his steam-engine improvements. "May I be allowed the subject of the former resolutions, equally applicable to to avail myself of this public opportunity to rectify that misthat he now held in his hand, and in which he most cordially apprehension: In the course of several conversations which concurred. There were undoubtedly classes in the community I had the honour of enjoying with Mr. Watt, on the nature maior from having more directly benefited by the discoveries and force of steam at different temperatures, he informed me, of Mt. Watt, were more particularly called upon this day with his characteristic mildness, that his friend Professor but surely in such a city as this, much of its prosperity may pupil of Dr. Black at the time of his improving the steam. be ascribed to the discoveries of that illustrious individual

, engine ; for that he never was a student of that philosopher, and which has the honour of claiming him as a citizen : it was * Ås to the latent heat of steam," said Mr. Wali to me, “it not too much to expect not only a liberal, but a general sup

was a piece of knowledge essential to my inquiries, and I to the measure now about to be adopted. He concluded worked it out myself in the best way that I could;' I used by moving the following resolution:

apothecaries' phiale for my apparatus, and by means of them III. "That, for the reasons stated in the second resolution, I got approxiinations suficient for my purpose at the time all ranks and classes in this city and neighbourhoort are parti: I With them I ascertained the two main ficts about steam

field.

first, that a cubic inch of water would form about a cubic foot element. Mr. Watt drew this, which was the legitimate conof ordinary steam; and, secondly, that the condensation of that clusion, from some experiments of Dr. Priestley and Mr. Warl. quantity of steam would heat six cubic inches of water from the tire, while these gentlemen made another and erroneous inferatmospheric temperature to the boiling point. Hence I saw ence. We are, therefore, come to express our admiration of a that six times the difference of temperature, or fully 900 de- mind great in original conception, admirabie execution, grees of heat, had been employed in giving elasticity to the most beneficial in its results ; a mind to which every coming steain ; which must be all abstracted before a compiete vacuum | age will lift ils eyes, as to one of the leading stars of British

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could be produced under the piston of the steam-engine." science. We are come to do reverence to a model of friendIt is not my intention to survey the philosophical researches ship, benevolence, and of every social virtue. We are assem. of Mr. Watt. I may merely suggest to this meeting, many bled for the purpose of erecting a memorial to departed worth, of whose members have been accustomed to regard him in which shall prove the strongest incentive to living industry the light only of a skilful engineer, that he has a joint claim and talent. And let

us never forget that Mr. Watt's genius had with the Honourable Mr. Cavendish, to the credit of one of the always useful objects in view. He lent himself to no parly greatest discoveries in pure science, that of the compound cabal, he displayed no love of power or popularity. of this nature of water ; a body, till modern times, accounted an the strongest proof is, his gliding

into a private tomb as James

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