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species. In some plants, as for instance, the large forest-trees, it is soft in texture and of but little importance, but reeds, grasses, canes, and most plants with hollow stems, are materially strengthened by the cuticle; in these cases it is almost entirely composed of silex, (flint,) which in some kinds of cane is in sufficient quantity to produce sparks when struck by a steel; under the microscope it has the appearance of a net-work of glass.

These being the organs by which nourishment is conveyed to various parts of the plant, we have next to ascertain the sources from which this nourishment is obtained, and the various descriptions of food supplied to different kinds of plants; and if we have been delighted with the mechanical beauty of the construction of the vegetable kingdom, we shall be more surprised even at the little we have discovered of the wonderful chemical operations that are constantly going on in the fluids during their circulation, by which water, perfectly tasteless and colourless when first taken up by the roots, assumes all the forms of acids, alkalies, gums, sugar, starch, and resins in infinite variety; and imparts to the different parts of the vegetable, colours of every hue.

Besides affording to mankind and to the brute creation much wholesome food, the simple growth of a plant assists in preserving the purity of the air. Every animal requires for its support a certain kind of air called oxygen; without its presence, life would cease. Every time the breath is drawn, a certain quantity of the atmospheric air is inhaled, and after it has been exposed to the surface of the lungs, it is returned to the atmosphere in a very altered state; the oxygen it contained is gone, and another kind of air called carbon, is found in its place: this latter air, if breathed, would instantly destroy life, so that if there was no counteracting cause, in process of time, the whole of the oxygen, the life-supporting property of the air, would be consumed, and its place supplied by the destructive air carbon; to remedy this, it has been wisely ordained, that while animals are constantly consuming oxygen and evolving carbon, plants should be performing an operation diametrically opposed to this, that is, consuming carbon and giving out oxygen. A kind of feeling, somewhat resembling instinct, was once attributed to plants, which was said to cause them to direct their roots downwards; but it has been shown that gravity, that is, the attraction of the earth, the power which causes a stone to fall, is the cause of the descent of the root, and that if this power is counteracted in any manner, the root will take a different direction.

The following curious experiment was made to illustrate this matter. A number of scarlet beans were placed on the circumference of a wheel, and well supplied with moisture; the wheel was then

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constantly kept in rapid motion, and the result was, that the roots were all directed outwards, and the leaves towards the centre. When the wheel was placed horizontally, and the motion was not sufficiently rapid to overcome entirely the power of gravity, the roots and leaves assumed the position represented in the next engraving.

In this case, the power that prevented the roots descending, and caused them to take a horizontal position, was what is called the centrifugal force; that is, the tendency which all substances have to fly off from the centre round which they revolve; the same power in fact by which a stone flies with violence from a sling after it has been whirled rapidly round the head of the slinger. clear that the direction of the root downwards does not arise from any property possessed by the plant itself, but from some entirely distinct directive force, which force is in the case of a plant gravity; and, that if two directive forces are brought into action at the same time, it follows the direction of the most powerful.

So that it is

If we observe the outward appearance of a plant, we see that it consists of root, stem, leaves, flowers, and fruit; the roots, as we all know, are directed downwards, and obtain from the earth the nourishment which is required for the growth of the plant; this rises in the vessels by what is called capillary attraction. The property of raising liquids above their natural level is possessed by all extremely small tubes, which are called capillary (hair-like) tubes, the rise of the sap is also assisted by the expansion and contraction of the silver grain, which takes place from the effect of the sun's rays during the day, and the coldness of the air in the night.

That the sap rises in the vessels contained in the alburnum, and after it has circulated through the leaves, and undergone many changes by the action of the atmosphere, descends along the fibrous portion of the bark, is made manifest by removing a small portion of the bark of a tree; when it will be seen, that the sap will flow in much greater quantity from the upper part of the wound, than from the lower.

The vessels which have been discerned in the trunk, and the various parts of which it consisted, are continued, although of course much reduced in size, through every branch and leaf-stalk, and even through the leaf itself, and the greatest portion of these parts can be displayed by careful dissection.

The following engraving is a magnified view of a series of the spiral tubes, the trachea, continued through the centre of a leaf.

Although the presence of water and air is sufficient to cause a seed to vegetate, yet, in order that it should flourish and produce seed, the water ought to hold in solution decayed vegetable and animal substances. The greater or lesser quantity of these substances is one of the chief causes of the fruitfulness or sterility of land, and to

supply the want of these, recourse is had to various kinds of manure

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FAMILIAR ILLUSTRATIONS OF EXPERI

MENTAL SCIENCE.

No. V. HEAT. RADIATION. CONDUCTION. THE rate at which heat is radiated is dependent, in a remarkable degree, on the colour, and other conditions of the surfaces of bodies.

increased. Black-lead, with which stoves are usually polished, could be very well dispensed with, were it not, that in this instance, as in many others, we cheerfully surrender a little scientific propriety, rather than part with our early associations and habits of cleanliness.

Nothing is more difficult than to form an accurate estimate of the temperature of different substances, by means of our ordinary perceptions. If we would avoid frequent mistakes on this subject, we must constantly submit our sensations to the correction of our judgment.

Heat and cold, as ordinarily experienced by us, depend on the previous temperature of the particular parts of the body, in which these sensations may be induced; and the temperature, and rate of conduction possessed by the substance with which such parts may be in contact.

If any quantity, say, for instance, a pint of boiling water be poured into a polished metal tea-pot, and an equal quantity of water, at the same temperature, into a rough black earthenware tea-pot, both the vessels standing in the same room, and at no great distance from each other, the water in the earthenware pot will cool down to the temperature of the surrounding air, in less time than that in the metal pot. For a polished metal pot, if we substitute one whose exterior has become rough and tarnished by neglect or ill usage, the water will be found to cool quicker in that than in the other. In addition to the last-mentioned metal-pot being rough and dis-under-ground cellar, or arched vault, the included coloured, if it be painted black, or some dark colour, the rate of cooling of the contained water will thereby be still further accelerated; but it will be less rapid than in the earthenware-pot.

Hence we may learn, that a metallic tea-pot is the most useful, as respects keeping the tea hot, but, to insure all its advantages, it should be kept clean and well polished. The same will apply to tea-kettles and various other culinary vessels. Those which are kept clean and bright will retain the heat of water, or other liquids, contained in them, much longer than those whose exterior surfaces are rough and discoloured.

The circumstances that assist in determining the rate at which heat is disengaged from the surfaces of bodies, operate equally favourably upon that which is directed towards those surfaces. Any substance that radiates heat rapidly, will absorb it in the same proportion, provided that, in each case, the conditions are alike favourable. Those substances whose surfaces are smooth and bright, and of a light colour, reflect heat; that is, they turn it aside from its straight course, and thus interrupt its progress. Those substances whose surfaces are rough and darkcoloured, radiate and absorb heat. Hence that substance which reflects heat the most perfectly, is the very worst that can be selected for its radiation or absorption. Water, or any other liquid, may be made to boil in less time, all other circumstances being the same, in a rough and discoloured metallic vessel, than in one whose outside is perfectly clean and bright. If the metallic and earthenware teapots already mentioned, be both filled with cold water, say at the temperature of 45°, and placed in a room whose temperature is 70°, the water in the earthenware pot will acquire the temperature of the air in the room in less time than that in the polished metal pot; proving that the same conditions influence the absorption of heat that, in the first cited experiments, would be seen to determine its radiation.

In the houses of the wealthy, stoves are sometimes employed which are made of polished metal. This is the most injudicious arrangement that could possibly be devised for heating the apartments in which such stoves are fixed. On the same principle, it is improper to surround a fire-place with porcelain tiles, or, if we wish our feet to receive any benefit from a fire, to place in front of it a polished fender. Rough, and dark-coloured surfaces, are best adapted for domestic stoves. Such stoves are not only the most useful, but the most economical, since in diffusing heat into the apartment by radiation, the benefits of the ignited fuel in the grate are materially

On a cold day in winter, if we descend into an

f

air will communicate a sensation of warmth. On a warm day in summer, air at the same temperature, in the same cellar or vault, will produce the opposite sensation of cold. In winter, the external air being at a lower temperature than that in the vault, we pass from a cold to a warm medium. In summer, the air in the vault will be at a lower temperature than the external air, and we consequently pass from a warm to a cold medium. Notwithstanding the apparent contradictions in our sensations, it rarely happens, that the temperature of the air in a cellar or vault, is so high in winter as it is in summer. If we were to judge only by its effects on our body, we should pronounce a different decision.

On examining dissimilar substances in the same room, with a view to ascertain their temperatures, if we have no better guide than our sensations, we shall arrive at very incorrect conclusions. Placing the hand successively in contact with a carpet, a table, a marble slab, and a polished brass or iron fender, we shall, in the absence of any other information, than that derived from our feelings, pronounce the table to be colder than the carpet, the marble slab to be colder than the table, and the fender to be colder than the marble. A thermometer will inform us, that the several articles we have enumerated are all at an equal temperature. The different sensations produced by them, are, therefore, entirely due to the difference in their rates of conducting heat.

Wool is denominated a bad conductor. The heat in the hand placed in contact with a carpet, will pass through, or among the fibres of the wool, but very slowly. Wood is a bad conductor, but it conducts more rapidly than wool. Compared with the carpet, the table will feel cold, because in a given time, a greater quantity of heat will pass from the hand to the table, than from the hand to the carpet. Marble is classed among bad, or imperfect conductors of heat, but it possesses this property in a more eminent degree than either of the before-mentioned substances. Metals are good conductors. The fender, therefore, will feel colder than the other articles, because, in a given time, it will abstract, or carry away from the hand, a greater quantity of heat than either the carpet, the table, or the marble slab.

A substance whose surface is smooth or polished, will excite the sensation of cold in a more intense degree than another substance, or a different part of the same substance, at the same temperature, whose surface is rough and irregular. This effect is chiefly mechanical, and it is occasioned by the more perfect

contact that takes place between the hand and a smooth surface, than one which is rough and irregular.

From what has been stated in a former paper, our readers will have no difficulty in understanding, that these observations are as applicable to our sensations of heat, as they are to those of cold. We may place the hand in contact with a bad conductor of heat without experiencing pain, whilst similar contact with a good conductor, at the same temperature, will inflict a severe wound. In the first instance, the neat, moving slowly towards the hand, it is easily dissipated; in the second, its motion being rapid, it accumulates, and destroys the parts in its immediate vicinity. For these reasons, we perceive the propriety of adapting handles of wood to tea and coffee-pots, box-irons, and many other utensils that are employed at a high temperature. So, also, folds of woollen cloth, or of leather, are interposed between the hand and a heated metallic body, for the purpose of intercepting the heat. By constant exposure to the effects of a high temperature, the skin on the inside of the hands will become so thick and insensible, as to resist a degree of heat that would scorch to the bone an unpractised hand. Instances are recorded, of workmen employed in the smelting of

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copper, who could dip their hands into the liquid metal without experiencing pain. We knew a female servant, who was in the habit of taking vegetables and other articles of food from a saucepan or pot of boiling water, with her hands, instead of using a fork or a ladle.

Those persons who are exposed to a high temperature in their ordinary avocations, generally take the precaution to wear woollen clothing. Others, who voluntarily expose themselves to extraordinary degrees of heat, for the purpose of exciting wonder, or gaining a subsistence, are not endowed with any peculiar properties by which they resist its effects. Their secret consists in availing themselves of bad conducting substances, covering their bodies with woollen garments, shielding their feet by wooden clogs, and carefully avoiding contact with metals, or other conductors of heat. It is possible to remain a short time in a room, constructed for the purpose, whose temperature is sufficiently high to broil a steak. This has been done, without any great inconvenience, by men whose testimony may be implicitly relied on.

The following experiment will serve as a further illustration of our liability to be deceived, were we to trust to our sensations, in estimating the temperature of different substances :

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Let there be four vessels, arranged in the order de- | noted above; in 1, place a certain quantity of water, as cold as it can be obtained; in 2 and 3, each an equal quantity of water, moderately warm, or as nearly as possible, the temperature of the human body; in 4, also, an equal quantity of water, but as hot as the hand will conveniently bear: if we place both hands in the vessels 2 and 3 for a few minutes, they will be of an equal temperature; removing the right hand to 4 and the left hand to 1, we shall experience in the former the sensation of heat, in the latter that of cold. Now, if we suddenly remove the right hand from 4 to 3, and the left from 1 to 2, our sensations will be reversed; the right hand feeling cold, the left hand warm, although the temperature of the water

FALL OF A MOUNTAIN, AT A Swiss wedding-party arrived at Art, a village at the southern extremity of the lake of Zug, in Switzerland, for the purpose of spending their holiday in ascending a mountain called the Righi. The party divided as they went towards the village of Goldau, those in front being about two hundred paces in advance when they entered the village. The attention of their friends who were behind them was suddenly arrested by an extraordinary appearance, which they stopped to view through their telescopes. All at once, the whole mountain (the Rotzberg, or Ruffiberg, which was on the left of the village, and the summit, distant from it several leagues,) appeared to move; soon a shower of stones passed through the air over their heads with the rapidity of lightning, and they effected their safety only by a speedy flight. All their friends disappeared in an instant, and were buried under the ruins of Goldau, which is now covered by a hill of rocky fragments, an hundred feet high. Notwith

in both vessels is alike. This apparently contradictory phenomenon may be easily explained.' In the first instance, the hands are at a uniform temperature; but by placing the left hand in vessel 1, it will feel cold, because, the water being at a lower temperature than the hand, heat will pass from the hand to the water. The right hand, in 4, will feel warm, because the water being at a higher temperature than the hand, heat will pass from the water to the hand. Removing the right hand from 4 to 3, and the left from 1 to 2, the same sensations will be experienced, but at opposite sides of the body, the right hand now feeling cold, the left hand warm, whilst both are immersed in water of the same temperature.

R. R.

GOLDAU, IN SWITZERLAND. standing all the search made on that fatal spot, no vestiges of the unfortunate people could be found.

There are sufficient proofs that this was not the first slide of the mountains of that neighbourhood, though it was the most terrible of all these catastrophes. An enormous quantity of snow had fallen during the preceding winter, and the months of July and August had been extraordinarily rainy; the fall took place on the 2nd of September. During the 1st and 2nd, it had rained in torrents without ceasing; in the morning of the 2nd, the people in the neighbourhood, heard a noise and rumbling in the mountain; and other phenomena had been observed in different parts. At five o'clock in the afternoon, masses of rock were detached from the mountain, and precipitated with the crash of thunder into the valleys, where their ruins extended the whole length of the base of the Righi, to the breadth of 1000 feet; their height was 100 feet, and

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CHURCH AND BUILDINGS ERECTED ON THE SITE OF THE VILLAGE OF GOLDAU.

their length near a league. Large tracts of land, so charming and so fertile, were changed, in five minutes, into a frightful desert; the valleys were covered, for the space of a league square, with a chaos of hills, from 100 to 200 feet in height; the villages of Goldau, Busingen, Unter-Rothen, and Lowerz, were buried under the ruins; the western part of the lake of Lowerz was filled up, and the inhabitants of the vallies, so interesting on account of their beauty, their energy, their activity, and their frugality, were crushed under the fragments of the mountain, or plunged into dreadful misery. Of inhabitants of the valleys, four hundred and thirty three perished, besides sixteen from other parts of the canton, and the eight persons who composed the wedding-party; and three hundred and fifty more, who escaped with their lives, were left in a state of destitution and distress.

The masses of rock fell principally in four different directions, so that their fractured pieces formed four great lines of ruins. On the Ruffi, (called also the Rotzberg,) whole forests were overturned, and buried in the ruins of the mountain.

During the following winter, there fell again in the valley a quantity of blocks of stone and of trees, from the top of the mountain Steinbergerflue. For some time the water from rain and snow had diminished the adhesion of the parts of this bank of stone and clay; the continual rains of the preceding summer, but principally the torrents on the 1st of September, completed its destruction, and when the base began to give way, the strata of breccia, which it supported, necessarily broke away and fell. Thus this lamentable event was not, in its proper sense, a fall of the mountain or of rocks, but rather, a slide, or slip, of earth and

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their safety in flight. During many days, a little
island in the lake remained so deeply covered, that
only the tops of its trees were visible. On the other
isle, called Schevanaes, the water rose as high as the
clock in the tower of the chapel. The extraordinary
agitation of the lake continued for a quarter of an
hour. Its waves removed the chapel of Olten, near
Séven, and carried it away to near Steinen, half a
league from its former site. The village of Lowerz
was covered with fragments of the mountain, in
which every thing but the church-tower was buried.
[Abridged from EBEL'S Manuel du Voyageur en Suisse.]

THE WHITE OWL.

We have had, ever since I can remember, a pair of white owls that constantly breed under the eaves of this church. As I have paid good attention to the manner of life of these birds during their season of breeding, which lasts the summer through, the following remarks may not, per haps, be unacceptable.

About an hour before sunset (for then the mice begin to run), they sally forth in quest of prey, and hunt all round the hedges of meadows and small enclosures for them, In this irregular which seem to be their only food. country, we can stand on an eminence, and see them beat the fields over like a setting-dog, and often drop down in the grass or corn. I have minuted these birds with my watch for an hour together, and have found that they return to their nest, the one or the other of them, about once in five minutes; reflecting at the same time on the adroitness well-being of itself and offspring. that every animal is possessed of, as far as regards the

But a piece of address, which they show when they return loaded, should not, I think, be passed over in silence. As they take their prey with their claws, so they carry it in their claws to their nest: but, as the feet are necessary in their ascent under the tiles, they constantly perch first on the roof of the chancel, and shift the mouse from their claws to their bill, that the feet may be at liberty to take hold of the plate on the wall, as they are rising under the eaves. -WHITE'S Selborne.

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UNDER THE DIRECTION OF THE COMMITTEE OF GENERAL LITERATURE AND EDUCATION, APPOINTED BY THE SOCIETY FOR PROMOTING CHRISTIAN KNOWLEDGE.

SOME ACCOUNT OF THE RISE AND PROGRESS OF THE BRITISH ARMY.

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THE annals of the British Army, like those of the Navy, from the earliest periods of our history, abound with the most splendid and spirit-stirring passages. British valour, at the hour of trial, is equally distinguished ashore or afloat. "Our nation," remarks Dr. Johnson, "may boast, beyond any other people in the world, of a kind of epidemic bravery, diffused equally through all its ranks; which can show a peasantry of heroes, and fill our armies with clowns, whose courage may vie with that of the general." This is high praise, but it has truly been remarked, that the character of our army has been earned in battle and attested by victory; and that wherever it has been tolerably led, it has conquered. That these results have been owing to the physical strength and power of endurance, as well as to the innate bravery of our troops, cannot be disputed. A very eminent authority (Colonel Napier,) observes that this circumstance was strikingly apparent in 1815, when the robust nature and powerful frame of the British infantry soldier were distinguished, amidst the united armies of Europe. "He sustains," says the gallant officer, "fatigue and wet, and the extremes of cold and heat, with incredible vigour. When completely disciplined, and three years are required to accomplish this, his port is lofty, and his movements free; the whole world cannot produce a nobler specimen of military bearing; nor is the mind unworthy of the outward man. He does not indeed possess that presumptuous vivacity which would lead him to dictate to his commanders, or even to censure real errors, although he may perceive them, but he is observant and quick to comprehend his orders, full of reVOL. V.

sources under difficulties, calm and resolute in danger, and more than usually obedient and careful of his officers in moments of imminent peril. It has been asserted, that his unshaken firmness in battle is the result of a phlegmatic constitution, uninspired by moral feeling. Never was a more stupid calumny uttered. Napoleon's troops fought in bright fields, where every helmet caught some beams of glory; but the British soldier conquered under the cold shade of aristocracy; no honours awaited his daring, no despatch gave his name to the applauses of his countrymen. His life of danger was uncheered by hope, his death unnoticed. Did his heart sink therefore? Did he not endure, with surprising fortitude, the worst of ills, sustain the most terrible assaults in battle unmoved, and, with incredible energy, overthrow every opponent; at all times proving that, while no physical military qualification was wanting, the fount of honour was full and fresh within him? The result of one hundred battles, and the merited testimony of impartial writers of different nations, has given the first place amongst the European infantry to the British; but, in a comparison between the troops of France and England, it would be unjust not to admit that the cavalry of the former stand higher in the estimation of the world."

To notice the splendid achievements, which have called forth this just and eloquent eulogium, forms no part, however, of the present paper; for it is scarcely necessary to say, that even a bare enumeration of the most interesting events, much less a connected outline of British military history, would very far exceed the limits which are assigned

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