« AnteriorContinuar »
species." In some plants, as for instance, the large constantly kept in rapid motion, and the result was, forest-trees, it is soft in texture and of but little that the roots were all directed outwards, and the importance, but reeds, grasses, canes, and most plants leaves towards the centre. When the wheel was placed with hollow stems, are materially strengthened by horizontally, and the motion was not sufficiently rapid the cuticle; in these cases it is almost entirely to overcome entirely the power of gravity, the roots composed of silex, (ilint,) which in some kinds of and leaves assumed the position represented in the cane is in sufficient quantity to produce sparks when next engraving. struck by a steel ; under the microscope it has the In this case, the power that prevented the roots appearance of a net-work of glass.
descending, and caused them to take a horizontal These being the organs by which nourishment is position, was what is called the conveyed to various parts of the plant, we have next centrifugal force; that is, the tento ascertain the sources from which this nourish-dency which all substances have ment is obtained, and the various descriptions of to fly off from the centre round food supplied to different kinds of plants; and if which they revolve; the same we have been delighted with the mechanical beauty power in fact by which a stone of the construction of the vegetable kingdom, we flies with violence from a sling shall be more surprised even at the little we have after it has been whirled rapidly discovered of the wonderful chemical operations that round the head of the slinger. So that it is are constantly going on in the fluids during their clear that the direction of the root downwards does circulation, by which water, perfectly tasteless and not arise from any property possessed by the plant colourless when first taken up by the roots, assumes itself, but from some entirely distinct directive force, all the forms of acids, alkalies, gums, sugar, starch, which force is in the case of a plant gravity; and, and resins in infinite variety; and imparts to the that if two directive forces are brought into action at different parts of the vegetable, colours of every the same time, it follows the direction of the most hue.
powerful. Besides affording to mankind and to the brute crea If we observe the outward appearance of a plant, tion much wholesome food, the simple growth of a plant we see that it consists of root, stem, leaves, flowers, assists in preserving the purity of the air. Every and fruit; the roots, as we all know, are directed animal requires for its support a certain kind of air downwards, and obtain from the earth the nourishcalled oxygen ; without its presence, life would cease. ment which is required for the growth of the plant; Every time the breath is drawn, a certain quantity of the this rises in the vessels by what is called capillary atmospheric air is inhaled, and after it has been exposed attraction. The property of raising liquids above to the surface of the lungs, it is returned to the their natural level is possessed by all extremely atmosphere in a very altered state; the oxygen it con small tubes, which are called capillary Chair-like) tained is gone, and another kind of air called carbon, tubes, the rise of the sap is also assisted by the exis found in its place: this latter air, if breathed, pansion and contraction of the silver grain, which would instantly destroy life, so that if there was no takes place from the effect of the sun's rays during counteracting cause, in process of time, the whole of the day, and the coldness of the air in the night. the oxygen, the life-supporting property of the air, That the sap rises in the vessels contained in the would be consumed, and its place supplied by the alburnum, and after it has circulated through the destructive air carbon; to remedy this, it has been leaves, and undergone many changes by the action wisely ordained, that while animals are constantly of the atmosphere, descends along the fibrous porconsuming oxygen and evolving carbon, plants should tion of the bark, is made manifest by removing be performing an operation diametrically opposed to a small portion of the bark of a tree; when it will this, that is, consuming carbon and giving out oxygen. be seen, that the sap will flow in much greater quanA kind of feeling, somewhat resembling instinct, was tity from the upper part of the wound, than from once attributed to plants, which was said to cause them the lower. to direct their roots downwards; but it has been The vessels which have been discerned in the shown that gravity, that is, the attraction of the earth, trunk, and the various parts of which it consisted, are the power which causes a stone to fall, is the cause continued, although of course much reduced in size, of the descent of the root, and that if this power through every branch and leaf-stalk, and even is counteracted in any manner, the root will take a through the leaf itself, and the greatest portion of different direction.
these parts can be displayed by careful dissection. The following curious experiment was made to The following engraving is a magnified view of a illustrate this matter. A number of scarlet beans series of the spiral tubes, the tracheæ, continued were placed on the circumference of a wheel, and through the centre of a leaf. well supplied with moisture; the wheel was then Although the presence of water and air is sufficient
to cause a seed to
FAMILIAR ILLUSTRATIONS OF EXPERI increased. Black-lead, with which stoves are usually MENTAL SCIENCE.
polished, could be very well dispensed with, were it
not, that in this instance, as in many others, we No. V. HEAT. RADIATION. CONDUCTION.
cheerfully surrender a little scientific propriety, rather The rate at which heat is radiated is dependent, in a than part with our early associations and habits of remarkable degree, on the colour, and other condi. cleanliness. tions of the surfaces of bodies.
Nothing is more difficult than to form an accurate If any quantity, say, for instance, a pint of boiling estimate of the temperature of different substances, water be poured into a polished metal tea-pot, and by means of our ordinary perceptions. If we would an equal quantity of water, at the same temperature, avoid frequent mistakes on this subject, we must into a rough black earthenware tea-pot, both the constantly submit our sensations to the correction of vessels standing in the same room, and at no great our judgment. distance from each other, the water in the earthen Heat and cold, as ordinarily experienced by us, ware pot will cool down to the temperature of the depend on the previous temperature of the particular surrounding air, in less time than that in the metal parts of the body, in which these sensations may be pot. For a polished metal pot, if we substitute one induced; and the mperature, and rate of conducwhose exterior has become rough and tarnished by tion possessed by the substance with which such neglect or ill usage, the water will be found to cool parts may be in contact. quicker in that than in the other. In addition to
On a cold day in winter, if we descend into an 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, air will communicate a sensation of warmth. On a the rate of cooling of the contained water will warm day in summer, air at the same temperature, thereby he still further accelerated ; but it will be in the same cellar or vault, will produce the opposite less rapid than in the earthenware-pot.
sensation of cold. In winter, the external air being Hence we may learn, that a metallic tea-pot is the at a lower temperature than that in the vault, we most useful, as respects keeping the tea hot, but, to pass from a cold to a warm medium. In summer, insure all its advantages, it should be kept clean and the air in the vault will be at a lower temperature well polished. The same will apply to tea-kettles than the external air, and we consequently pass from and various other culinary vessels. Those which are a warm to a cold medium. Notwithstanding the kept clean and bright will retain the heat of water, apparent contradictions in our sensations, it rarely or other liquids, contained in them, much longer than happens, that the temperature of the air in a cellar those whose exterior surfaces are rough and dis or vault, is so high in winter as it is in summer, If coloured.
we were to judge only by its effects on our body, we The circumstances that assist in determining the should pronounce a different decision. rate at which heat is disengaged from the surfaces of On examining dissimilar substances in the same bodies, operate equally favourably upon that which room, with a view to ascertain their temperatures, if is directed towards those surfaces. Any substance we have no better guide than our sensations, we that radiates heat rapidly, will absorb it in the same shall arrive at very incorrect conclusions. Placing proportion, provided that, in each case, the conditions the hand successively in contact with a carpet, a are alike favourable. Those substances whose sur- table, a marble slab, and a polished brass or iron faces are smooth and bright, and of a light colour, fender, we shall, in the absence of any other inforreflect heat; that is, they turn it aside from its mation, than that derived from our feelings, prostraight course, and thus interrupt its progress. nounce the table to be colder than the carpet, the Those substances whose surfaces are rough and dark- marble slab to be colder than the table, and the coloured, radiate and absorb heat. Hence that sub- fender to be colder than the marble. A thermometer stance which reflects heat the most perfectly, is the will inform us, that the several articles we have very worst that can be selected for its radiation or enumerated are all at an equal temperature. The absorption. Water, or any other liquid, may be different sensations produced by them, are, therefore, made to boil in less time, all other circumstances entirely due to the difference in their rates of conbeing the same, in a rough and discoloured metallic ducting heat. vessel, than in one whose outside is perfectly clean Wool is denominated a bad conductor. The heat and bright. If the metallic and earthenware tea- in the hand placed in contact with a carpet, will pots already mentioned, be both filled with cold pass through, or among the fibres of the wool, but water, say at the temperature of 45°, and placed in very slowly. Wood is a bad conductor, but it a room whose temperature is 70°, the water in the conducts more rapidly than wool. Compared with earthenware pot will acquire the temperature of the the carpet, the table will feel cold, because in a given air in the room in less time than that in the polished time, a greater quantity of heat will pass from the metal pot; proving that the same conditions influence hand to the table, than from the hand to the carpet. the absorption of heat that, in the first cited experi- Marble is classed among bad, or imperfect conducments, would be seen to determine its radiation. tors of heat, but it possesses this property in a more
In the houses of the wealthy, stoves are sometimes eminent degree than either of the before-mentioned employed which are made of polished metal. This substances. Metals are good conductors. The is the most injudicious arrangement that could fender, therefore, will feel colder than the other possibly be devised for heating the apartments in articles, because, in a given time, it will abstract, or which such stoves are fixed. On the same principle, carry away from the hand, a greater quantity of it is improper to surround a fire-place with porcelain heat than either the carpet, the table, or the marble tiles, or, if we wish our feet to receive any benefit slab. from a fire, to place in front of it a polished fender. A substance whose surface is smooth or polished, Rough, and dark-coloured surfaces, are best adapted will excite the sensation of cold in a more intense for domestic stoves. Such stoves are not only the degree than another substance, or a different part of most useful, but the most economical, since in diffu- the same substance, at the same temperature, whose sing heat into the apartment by radiation, the surface is rough and irregular. This effect is chiefly benefits of the ignited fuel in the grate are materially | mechanical, and it is occasioned by the more perfect
contact that takes place between the hand and a copper, who could dip their hands into the liquid smooth surface, than one which is rough and irre- metal without experiencing pain. We knew a female gular.
servant, who was in the habit of taking vegetables From what has been stated in a former paper, our and other articles of food from a saucepan or pot of readers will have no difficulty in understanding, that boiling water, with her hands, instead of using a fork these observations are as applicable to our sensations or a ladle. of heat, as they are to those of cold.
Those persons who are exposed to a high temperaplace the hand in contact with a bad conductor of ture in their ordinary avocations, generally take the heat without experiencing pain, whilst similar contact precaution to wear woollen clothing. Others, who with a good conductor, at the same temperature, will voluntarily expose themselves to extraordinary deinflict a severe wound. In the first instance, the grees of heat, for the purpose of exciting wonder, or neat, moving slowly towards the hand, it is easily gaining a subsistence, are not endowed with any dissipated; in the second, its motion being rapid, peculiar properties by which they resist its effects. it accumulates, and destroys the parts in its imme- Their secret consists in availing themselves of bad diate vicinity. For these reasons, we perceive the conducting substances, covering their bodies with propriety of adapting handles of wood to tea and woollen garments, shielding their feet by wooden coffee-pots, box-irons, and many other utensils that clogs, and carefully avoiding contact with metals, or are employed at a high temperature. So, also, folds other conductors of heat. It is possible to remain of woollen cloth, or of leather, are interposed between a short time in a room, constructed for the purpose, the hand and a heated metallic body, for the purpose whose temperature is sufficiently high to broil a steak. of intercepting the heat. By constant exposure to This has been done, without any great inconvenience, the effects of a high temperature, the skin on the by men whose testimony may be implicitly relied on. inside of the hands will become so thick and insen The following experiment will serve as a further sible, as to resist a degree of heat that would scorch illustration of our liability to be deceived, were we to to the bone an unpractised hand. Instances are trust to our sensations, in estimating the temperature recorded, of workmen employed in the smelting of of different substances : 1
Let there be four vessels, arranged in the order de- , in both vessels is alike., (This apparently contranoted above; in 1, place a certain quantity of water, as dictory phenomenon may 'be easily explained. In cold as it can be obtained ; in 2 and 3, each an equal the first instance, the hands are at a uniform temquantity of water, moderately warm, or as nearly as perature; but by placing the left hand in vessel 1, it possible, the temperature of the human body; in 4, will feel cold, because, the water being at a lower temalso, an equal quantity of water, but as hot as the perature than the hand, heat will pass from the hand hand will conveniently bear : if we place both hands to the water. The right hand, in 4, will feel warm, in the vessels 2 and 3 for a few minutes, they will be because the water being at a higher temperature than of an equal temperature ; removing the right hand the hand, heat will pass from the water to the hand. to 4 and the left hand to 1, we shall experience in Removing the right hand from 4 to 3, and the left the former the sensation of heat, in the latter that of from 1 to 2, the same sensations will be experienced, cold. Now, if we suddenly remove the right hand but at opposite sides of the body, the right hand from 4 to 3, and the left from 1 to 2, our sensations now feeling cold, the left hand warm, whilst both will be reversed; the right hand feeling cold, the left are immersed in water of the same temperature. hand warm, although the temperature of the water
FALL OF A MOUNTAIN, AT GOLDAU, IN SWITZERLAND. A Swiss wedding-party arrived at Art, a village at the standing all the search made on that fatal spot, no southern extremity of the lake of Zug, in Switzerland, vestiges of the unfortunate people could be found. for the purpose of spending their holiday in ascending There are sufficient proofs that this was not the a mountain called the Righi. The party divided as first slide of the mountains of that neighbourhood, they went towards the village of Goldau, those in front though it was the most terrible of all these catabeing about two hundred paces in advance when they strophes. An enormous quantity of snow had fallen entered the village. The attention of their friends during the preceding winter, and the months of who were behind them was suddenly arrested by July and August had been extraordinarily rainy ; an extraordinary appearance, which they stopped to the fall took place on the 2nd of September. During view through their telescopes. All at once, the the 1st and 2nd, it had rained in torrents without whole mountain (the Rotzberg, or Ruffiberg, which ceasing; in the morning of the 2nd, the people in was on the left of the village, and the summit, distant the neighbourhood, heard a noise and rumbling in from it several leagues,) appeared to move; soon a the mountain ; and other phenomena had been shower of stones passed through the air over their observed in different parts. At five o'clock in the heads with the rapidity of lightning, and they effected afternoon, masses of rock were detached from their safety only by a speedy flight. All their friends the mountain, and precipitated with the crash of disappeared in an instant, and were buried under the thunder into the valleys, where their ruins extended ruins of Goldau, which is now covered by a bill of the whole length of the base of the Righi, to the rocky fragments, an hundred feet high. Notwith breadth of 1000 feet; their height was 100 feet, and
CHURCH AND BUILDINGS ERECTED ON THE SITE OF THE VILLAGE OF GOLDAU. their length near a league. Large tracts of land, so their safety in flight. During many days, a little charming and so fertile, were changed, in five minutes, island in the lake remained so deeply covered, that into a frightful desert; the valleys were covered, for only the tops of its trees were visible. On the other the space of a league square, with a chaos of hills, isle, called Schevanaes, the water rose as high as the from 100 to 200 feet in height; the villages of Goldau, clock in the tower of the chapel. The extraordinary Busingen, Unter-Rothen, and Lowerz, were buried agitation of the lake continued for a quarter of an under the ruins; the western part of the lake of hour. Its waves removed the chapel of Olten, near Lowerz was filled up, and the inhabitants of the val- Séven, and carried it away to near Steinen, half a lies, so interesting on account of their beauty, their league from its former site. The village of Lowerz energy, their activity, and their frugality, were crushed was covered with fragments of the mountain, in under the fragments of the mountain, or plunged wbich every thing but the church-tower was buried. into dreadful misery. Of inhabitants of the valleys, [Abridged from EDEL's Manuel du Voyageur en Suisse.) 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
TAE WHITE OWL, hundred and fifty more, who escaped with their lives, We have had, ever since I can remember, a pair of white were left in a state of destitution and distress.
owls that constantly breed under the eaves of this church. The masses of rock fell principally in four dif- As I have paid good attention to the manner of life of ferent directions, so that their fractured pieces formed the summer through, the following remarks may not, per
these birds during their season of breeding, which lasts four great lines of ruins. On the Ruffi, (called also haps, be unacceptable. the Rotzberg,) whole forests were overturned, and About an hour before sunset (for then the mice begin to buried in the ruins of the mountain.
run), they sally forth in quest of prey, and hunt all round During the following winter, there fell again in the the hedges of meadows and small enclosures for them,
In this irregular valley a quantity of blocks of stone and of trees, from which seem to be their only food. the top of the mountain Steinbergerflue. For some time the fields over like a setting-dog, and often drop down in
country, we can stand on an eminence, and see them beat the water from rain and snow had diminished the ad. the grass or corn. I have minuted these birds with my hesion of the parts of this bank of stone and clay; the watch for an hour together, and have found that they return continual rains of the preceding summer, but princi- to their nest, the one or the other of them, about once in pally the torrents on the 1st of September, completed five minutes; reflecting at the same time on the adroitness its destruction, and when the base began to give way, well-being of itself and offspring.
animal is possessed of, as far as regards the the strata of breccia, which it supported, necessarily
But a piece of address, which they show when they broke away and fell. Thus this lamentable event return loaded, should not, I think, be passed over in was not, in its proper sense, a fall of the mountain silence. As they take their prey with their claws, so they or of rocks, but rather, a slide, or slip, of earth and carry it in their claws to their nest: but, as the feet are stones.
necessary in their ascent under the tiles, they constantly The effects of this slide of the mountain on the 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 lake of Lowerz were prodigious. Its waters rose, as
to take hold of the plate on the wall, as they are rising if by the fury of a tempest, to the height of sixty or under the eaves. - WHITE's Selborne. seventy feet, in the direction of Séven, a village situated at the other end of the lake. A man, on an
LONDON: erinence, witnessed the terrific spectacle of the moun. JOHN WILLIAM PARKER, WEST STRAND. tains of water advancing towards the village of Séven, PUBLISHED IN WIZKLY NUMBERS, PRICE ONZ PENNT, AND IN MONTELY PARTE,
PRICE SIXPENCE, AND the inhabitants of which, warned by his cries, found Sold by all Booksellers and Newsvenden in the Kingdom.'
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.
The annals of the British Army, like those of the Navy, / sources under difficulties, calm and resolute in danger, and from the earliest periods of our history, abound with the more than usually obedient and careful of his officers in most splendid and spirit-stirring passages. British valour, moments of imminent peril. It has been asserted, that at the hour of trial, is equally distinguished ashore or his unshaken firmness in battle is the result of a phlegafloat. “Our nation," remarks Dr. Johnson, “ may boast, matic constitution, uninspired by moral feeling. Never beyond any other people in the world, of a kind of epi- was a more stupid calumny uttered. Napoleon's troops demic bravery, diffused equally through all its ranks; fought in bright fields, where every helmet caught some which can show a peasantry of heroes, and fill our armies beanrs of glory; but the British soldier conquered under with clowns, whose courage may vie with that of the the cold shade of aristocracy; no honours awaited his general." This is high praise, but it has truly been re- daring, no despatch gave his name to the applauses of his marked, that the character of our army has been earned in countrymen. His life of danger was uncheered by hope, battle and attested by victory; and that wherever it has his death unnoticed. Did his heart sink therefore ? Did been tolerably led, it has conquered. That these results he not endure, with surprising fortitude, the worst of ills, have been owing to the physical strength and power of sustain the most terrible assaults in battle unmoved, and, endurance, as well as to the innate bravery of our troops, with incredible energy, overthrow every opponent; at all cannot be disputed. A very eminent authority (Colonel times proving that, while no physical military qualification Napier,) observes that this circumstance was strikingly was wanting, the fount of honour was full and fresh within apparent in 1815, when the robust nature and powerful him? The result of one hundred battles, and the merited frame of the British infantry soldier were distinguished, testimony of impartial writers of different nations, has amidst the united armies of Europe. “He sustains," says given the first place amongst the European infantry to the the gallant officer, “ fatigue and wet, and the extremes of British; but, in a comparison between the troops of France cold and heat, with incredible vigour. When completely and England, it would be unjust not to admit that the disciplined, and three years are required to accomplish this, cavalry of the former stand higher in the estimation of the his port is lofty, and his movements free; the whole world world. cannot produce a nobler specimen of military bearing; nor To notice the splendid achievements, which have called is the mind unworthy of the outward man. He does not forth this just and eloquent eulogium, forms no part, howindeed possess that presumptuous vivacity which would ever, of the present paper; for it is scarcely necessary to lead him to dictate to his commanders, or even to censure say, that even a bare enumeration of the most interesting real errors, although he may perceive them, but he is events, much less a connected outline of British military observant and quick to comprehend his orders, full of re- history, would very far exceed the limits which are assigned Vol. V.