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chus caused to be placed at certain dis- This great truth limits the size and moditances along the high roads, after the ex- fies the shape of most productions of naample of the Greeks, large stones to assist ture and of art,-of hills, trees, animals, the horsemen in mounting.
architectural or mechanical structures,&c. Stone, John Hoskins, governor of Ma- Hills. Very strong or cohesive materiryland, distinguished himself in the revo- al may form hills of sublime elevation, lution. In early life, and at an early peri- with very projecting cliffs and very lofty od of the war, he was first captain in the perpendicular precipices ; and such are celebrated regiment of Smallwood. At seen, accordingly, where the hard granite the battles of Long Island, White Plains protrudes from the bowels of the earth, as and Princeton, he behaved with great in the Andes of America, the Alps of Eugallantry; and, at that of Germantown, he rope, the Himalayas of Asia, and the received a wound which disabled him for Mountains of the Moon in Central Africa. the residue of his life. But he still exert- But material of inferior strength exhibits ed himself in the service of his country, more humble risings and more rounded as a member of the executive council of surfaces. The gradation is so striking Maryland, until 1794, when he was chosen and constant from granite mountains governor, and remained so for three years down to those of chalk, or gravel, or sand, (as long a time as was allowed by the that the geologist can generally tell the constitution). He died at Annapolis, in substance of which a hill is composed by 1804, leaving behind him the reputation the peculiarities of its shape. 'Even in of an honest and honorable man, an in- granite itself, which is the strongest of trepid soldier, and a liberal, hospitable and rocks, there is a limit to height and profriendly citizen.
jection; and, if an instance of either, STRENGTH OF MATERIALS. [The fol- much more remarkable than now remains lowing article is extracted from Arnott's on earth, were by any chance to be proElements of Physics.) “ Strength depends duced again, the law which we are conon the magnitude, form and position of sidering would prune the monstrosity. bodies, as well as on the degree of cohesion The grotesque figures of rocks and mounin the material.”— Of similar bodies the tains seen in the paintings of the Chinese, largest is proportionally the weakest. Sup- or actually formed in miniature for their pose two blocks of stone left projecting gardens, to express their notions of perfrom a rock that has been hewn, of which fect sublimity and beauty, are caricatures blocks one is twice as long, and deep, and of nature, for which originals can never broad, as the other. The larger one will have existed. Some of the smaller islands by no means support as much more in the Eastern ocean, however, and some weight at its end than the other, as it is of the mountains of the chains seen in the larger; and for two reasons: 1. In the voyage towards China, along the coasts of larger, each particle of the surface of at- Borneo and Palawan, exhibit, perhaps, tachment, in helping to bear the weight the very limits of possibility in singular of the block itself, has to support by its shapes. In the moon, where the weight cohesion twice as many particles beyond or gravity of bodies is less than on the it, in the double extent of projection, as a earth, on account of her smaller size, particle has to support in the shorter mountains might be many times higher block; and, 2. both the additional sub- than on the earth; and observation proves stance, and any thing appended at the that the lunar mountains are much higher outer extremity of the larger, are acting than ours. By the action of winds, rains, with a double lever advantage to break it, currents and frost upon the mineral masses that is, to destroy the cohesion. Hence, around us, there is unceasingly going on if any such projection be carried out very anundermining and wasting of supports, so far, it will break off or fall by its own that every now and then immense rocks, weight alotte. What is thus true of a block or almost hills, are torn by gravity from supported at one end, is equally true of a the station which they have held since block supported at both ends, and, indeed, the earth received its present form, and of all masses, however supported, and of fall
in obedience to the law now explained. whatever forms. That a large body, The size of vegetables, of course, is obetherefore, may have proportionate strength dient to the same law. We have no trees to a smaller, it must be made still thicker reaching a height of 300 feet, even when and more clumsy than it is made longer; perfectly perpendicular, and sheltered in and, beyond a certain limit, no proportions forests that have been unmolested from whatever will keep it together, in opposi- the beginning of time; and oblique or tion merely to the force of its own weight. horizontal branches are kept within very
narrow limits by the great strength re- have scarcely a hundredth part of the bulk quired to support them. The truth that, of the timbers of a ship ten times as long to have proper strength, the breadth or di- as the boat. A ship's yard of ninety feet ameter in bodies must increase more quick- contains, perhaps, twenty times as much ly than the length, is well illustrated hy wood as a yard of thirty feet, and, even the contrast existing between the delicate then, is not so strong in proportion. If ten and slender proportions of a young oak or men may do the work of a three-hunelm, while yet in the seedsman's nursery, dred-ton ship, many more than three and its sturdy form when it has braved times that number will be required to for centuries all the winds of heaven, and manage a ship three times as large. Very has become the monarch of the park or large ships, such as the two built in Canaforest.
da in the year 1825, which carried each Animals furnish other interesting illus- nearly 10,000 tons, are weak from their trations of this law. How massive and size alone; and the loss of these two clumsy are the limbs of the elephant, the first specimens of gigantic magnitude will rhinoceros, the heavy ox, compared with not encourage the building of others like the slender forms of the stag, antelope and them. greyhound! And an animal much larger The degree in which the strength of than the elephant would fall to pieces structures is dependent on the form and from its own weight alone, unless its position of their parts, will be illustrated bones were made of much stronger ma- by considering the two cases of longituterials. Many have questioned whether dinal and transverse compression ; and the mammoth, or antediluvian elephant, the rule for giving strength will be found could have lived on dry land, or must to be, to cause the force tending to dehave been amphibious, that its great body stroy, to act, as equally as may be, on the might generally be borne up by water. whole resisting mass, at the same time, The whale is the largest of animals, but and with as little mechanical advantage as feels not its mighty weight because lying possible. In longitudinal compression, as constantly in the liquid support of the produced by a body on the top of a pillar,
A cat may fall with impunity the weight, while the support remains where an elephant or ox would be dashed straight, can only destroy the support by to pieces. The giants of the heathen my- crushing it in opposition to the repulsion thology could not have existed upon this and impenetrability of all its atoms. earth, for the reason which we are now Hence a very small pillar, if kept perfectly considering; although on our moon, straight, supports a very great weight; where, as already stated, weight is much but a pillar originally crooked, or beginless, such beings might be. In the plan- ning to bend, resists with only part of its et Jupiter, again, which is many times strength ; for the whole weight above larger than the earth, an ordinary man is supported on the atoms of the concave from hence would be carrying, in the side only, which are therefore in greater simple weight of his body, a load suffi- danger of being overpressed and crushed, cient to crush the limbs which supported while those on the convex side, separated him. The phrase a little compact man, from their natural helpm
are in the points to the fact that such a one is stronger opposite danger of being torn agunder. in proportion to his size than a taller man. The atoms near the centre, in such a case, The same law limits the height and are almost neutral, and might be absent breadth of architectural structures. In without the strength of the pillar being the houses of fourteen stories, which for- much lessened. Long pillars or supports merly stood under the castle of Edin- are weaker than short ones, because they burgh, there was danger of the superin- are more easily bent; and they are more cumbent wall crushing the foundation. easily bent because a very inconsiderable,
Roofs. Westminster hall approaches and therefore easily effected, yielding bethe limit of width that is possible without tween each two of many atoms, makes a very inconvenient proportions or central considerable bend in the whole ; while in supports; and the domes of the churches a very short pillar, there can be no bendof St. Peter, in Rome, and St. Paul, in ing without a great change in the relatior London, are in the same predicament. of proximate atoms, and such as can be
Arches of a Bridge. A stone arch much effècted only by great force. The weight larger than those of the magnificent or force bending any pillar may be conbridges in London, would be in danger of sidered as acting at the end of a long lecrushing and splintering its material. ver, reaching from the end of the pillar to
Ships. The ribs or timbers of a boat its centre, against the strength resisting at
a short lever from the side to the centre. a horizontal beam is supported at its exThe strength, therefore, has relation to tremities, its weight bends it down more the difference between these. Shortness, or less in the middle, the particles on the then, or any stay or projection at the side upper side being compressed, while the of the pillar, which, by making the resist- parts below are distended; and the bending lever longer, opposes bending, really ing and tendency to break are greater, acincreases the strength of a pillar. A col- cording as the beam is longer and its umn with ridges projecting from it is, on thickness or depth is less. The danger this account, stronger than one that is per- of breaking, in a beam so situated, is judgfectly smooth. A hollow tube of metal is ed of, by considering the destroying force stronger than the same quantity of metal as acting by the long lever reaching from in a solid rod, because its substance, the end of the beam to the centre, and the standing farther from the centre, resists resisting force or strength as acting only by with a longer lever. Hence pillars of cast- the short lever from the side to the centre, iron are generally made hollow, that they while only a little of the substance of the may have strength with as little metal as beam on the under side is allowed to resist possible. In the most perfect weighing- at all. This last circumstance is so rebeams for delicate purposes, that there markable, that the scratch of a pin on the may be the least possible weight with the under side of a plank resting as here suprequired strength, the arms, instead of be- posed, will sometimes suffice to begin the ing of solid metal, are hollow cones, in fracture. Because the resisting lever is which the metal is not much thicker than small in proportion as the beam is thinner, writing paper. Masts and yards for ships a plank bends and breaks more readily have been made hollow, in accordance than a beam, and a beam resting on its with the same principle. In nature's edge bears a greater weight than if resting works, we have to admire numerous il- on its side. Where a single beam cannot lustrations of the same class. The stems be found deep enough to have the strength of many vegetables, instead of being required in any particular case-os for round externally, are ribbed or angular supporting the roof of a house several and Auted, that they may have strength to beams are joined together, and in a great resist bending. They are hollow, also, as variety of ways, as is seen in house-ratters, in cornstalks, the elder, the bamboo of &c., which, although consisting of three tropical climates, &c., thereby combining or more pieces, may be considered as one lightness with their strength. A person very broad beam, with those parts cut out who visits the countries where the bam- which do not contribute much to the boo grows, cannot but admire the almost strength.—The arched form bears transendless uses to which its straightness, verse pressure so admirably, because, by lightness and hollowness, make it appli- means of it, the force that would destroy, cable among the inhabitants. Being found is made to compress all the atoms or parts of all sizes, it has merely to be cut into at once, and nearly in the same degree. pieces of the lengths required for any pur- The atoms on the under side of an arch, pose ; and nature has already been the resting against immovable abutments, turner, and the polisher, and the borer, must be compressed about as much as &c. In many of the Eastern islands, those on the upper side, and cannot therebamboo is the chief material of the ordi- fore be torn or overcome separately. The nary dwellings, and of the furniture,—the whole substance of the arch, therefore, refanciful chairs, couches, beds, &c. Flutes sists, almost like that of a straight pillar and other wind instruments there are under a weight, and is nearly as strong. merely pieces of the reed, with holes bor- To be able to adapt the curve to the size ed at the requisite distances. Conduits for of an arch, and to the nature of the matewater are pipes of bamboo; bottles and rial, requires in the architect a perfect accasks for preserving liquids are single quaintance with measures, &c. An error joints of larger bamboo, with their parti- which has been frequently committed by tions remaining; and bamboo, split into bridge-builders is, the neglecting to conthreads, is twisted into rope, &c. From sider sufficiently the effect of the horizonthe animal kingdom, also, we have illus- tal thrust of the arch on its piers. Each trations of our present subject-the hol- arch is an engine of oblique force, pushlow stiffness of the quills of birds; the hol. ing the pier away from it. In some inlow bones of birds; the bones of animals stances, one arch of a bridge falling, has generally, strong and hard, and often an- allowed the adjoining piers to be pushed gular externally, with light cellular texture down towards it, by the thrust, no longer within, &c.— Transverse Pressure. When balanced, of the arches beyond, and the whole structure has given way at once, common egg-shell is another example of like a child's bridge built of cards. It is the same class : what hard blows of the not known at what time the arch was in- spoon or knife are often required to penevented, but it was in comparatively modern trate this wonderful defence provided for uines. The hint inay have been taken from the dormant life! The weakness of a nature ; for there are instances, in alpine similar substance, which has not the countries, of natural arches, where rocks arched form, is seen in a scale from a have fallen between rocks, and have there piece of freestone, which so readily crumbeen arrested and suspended, or where bles between the fingers. To determine, burrowing water has at last formed a wide for particular cases, the best forms of passage under masses of rock, which re- beams and joists, and of arches, domes, inain balanced, among themselves, as an &c., is the business of strict calculation, arch above the stream. Nothing can sur- and belongs, therefore, to mathematics, or pass the strength and beauty of some the science of measures. It was a beauinodern stone bridges—those, for instance, tiful problem of this kind, which Mr. which span the Thames as it passes Smeaton, the English engineer, solved so through London. Iron bridges have been perfectly in the construction of the farmade with arches twice as large as those famed Eddystone light-house. (See Lightof stone, the material being more tena- House.) cious, and calculated to form a lighter STRENGTH, FEATS OF. Doctor Brewswhole. That of three fine arches, between ter, in his work on Natural Magic, gives the city of London and Southwark, is a some striking instances of muscular noble specimen; and, compared with the strength, and also of the effects produced bridges of half a century ago, it appears by applying the principles of the mechanialmost a fairy structure of lightness and cal powersto the human frame, from which grace. The great domes of churches, as we extract the following :-Firmus, a nathose of St. Peter's in Rome and St. Paul's tive of Seleucia, who was executed by in London, have strength on the same the emperor Aurelian for espousing the principle as simple arches. They are, cause of Zenobia, was celebrated for his in general, strongly bound at the bottom feats of strength. In his account of the with chains and iron bars, to counteract life of Firmus, who lived in the third the horizontal thrust of the superstructure. century, Vopiscus informs us, that he The Gothic arch is a pointed arch, and is could suffer iron to be forged upon an calculated to bear the chief weight on its anvil placed upon his breast. summit or key-stone. Its use, therefore, this, he lay upon bis back, and, resting his is not properly to span rivers as a bridge, feet and shoulders against some support, but to enter into the composition of varied his whole body formed an arch, as we pieces of architecture. With what effect shall afterwards more particularly explain. it does this, is seen in the truly sublime Until the end of the sixteenth century, the Gothic structures which adoru so many exhibition of such seats does not seem to parts of Europe. The following are in- have been common.
About the year stances, in smaller bodies, of strength ob- 1703, a native of Kent, of the name of tained by the arched form: A thin watch- Joyce, exhibited such feats of strength in glass bears a very hard push; a dished or London and other parts of England, that arched wheel for a carriage is many times he received the name of the second Samstronger to resist all kinds of shocks than His own personal strength was very a perfectly flat wheel; a full cask may fall great; but he had also discovered, with. with impunity where a strong square box out the aid of theory, various positions would be dashed to pieces; a very thin of the body, in which men even of comglobular flask or glass, corked and sent mon strength could perform very surdown many fathoms into the sea, will resist prising feats. He drew against horses, the pressure of water around it, where a and raised enormous weights; but as he square bottle, with sides of almost any actually exhibited his power in ways which thickness, would be crushed to pieces. evinced the enormous strength of his own We have an illustration, from the animal muscles, all liis feats were ascribed to the frame, of the arched form giving strength, same cause. In the course of eight or in the cranium or skull, and particularly ten years, however, his methods were in the skull of man, which is the largest discovered, and many individuals of orin proportion to its thickness: the brain dinary strength exhibited a number of his required the most perfect security, and, principal performances, though in a manby the arched form of the skull, this has ner greatly inferior to Joyce. Some time been obtained with little weight. The afterwards, John Charles van Eckeberg,
a native of Harzgerode, in Anhalt, trav- rising up and down while the performer elled through Europe, under the appella- breathed. A stone one and a half feet tion of Samson, exhibiting very remarka- long, one foot broad, and half a foot chick, ble examples of his strength. This, we was then laid upon his belly and broken believe, is the same person whose feats by a sledge-hammer—an operation which are particularly described by doctor De- was performed with much less danger saguliers. He was a man of the middle size, than when his back touched the ground. and of ordinary strength ; and, as doc- 5. His next feat was to lie down on the tor Desaguliers was convinced that his ground. A man being then placed on feats were exhibitions of skill, and not of his knees, he drew his heels towards his strength, he was desirous of discovering body, and, raising his knees, he lifted up his methods; and, with this view, he went the man gradually, till, having brought his lo see him, accompanied by the marquis knees perpendicularly under him, he raised of Tullibardine, doctor Alexander Stuart, his own body up, and, placing his arms and doctor Pringle, and his own mechan- around the man's legs, rose with him, ical operator. They placed themselves and set him down on some low table or round the German so as to be able to ob- eminence of the same height as his knees. serve accurately all that he did; and their This feat he sometimes performed with success was so great, that they were able two men in place of one. 6. In his last, to perform most of the feats the same and apparently most wonderful performevening by themselves, and almost all the ance, he was elevated on a frame work, and rest when they had provided the proper supported a heavy cannon placed upon a apparatus. Doctor Desaguliers exhibited scale at some distance below him, which some of the experiments before the royal was fixed to a rope attached to his girdle. society, and has given such a distinct ex- Previous to the fixing of the scale to the planation of the principles on which they rope attached to his girdle, the cannon depend, that we shall endeavor to give a and scale rested upon rollers; but when all popular account of them. 1. The performn- was ready, the rollers were knocked away, er sat upon an inclined board with his feet a and the cannon remained supported by little higher than his hips. His feet were the strength of his loins. These feats may placed against an upright board well se- be briefly explained thus:-The feats No. cured. Round his loins was placed a 1, 2 and 6, depend entirely on the natural strong girdle with an iron ring in front. strength of the bones of the pelvis, which To this ring a rope was fastened. The form a double arch, wbich it would rerope passed between his legs through a quire an immense force to break, by any hole in the upright board, against which external pressure directed to the centre his feet were braced, and several men or of the arch; and as the legs and thighs two horses, pulling on the rope, were una- are capable of sustaining four or five ble to draw him out of his place. 2. He thousand pounds when they stand quite also fastened a rope to a high post, and, upright, the performer has no difficulty having passed it through an iron eye fixed in resisting the force of two horses, or in the side of the post some feet lower in sustaining the weight of a cannon down, secured it to his girdle. He then weighing two or three thousand pounds. planted his feet against the post near the The feat of the anvil is certainly a very iron eye, with his legs contracted, and, surprising one. The difficulty, however, suddenly stretching out his legs, broke really consists in sustaining the anvil; for the rope, and fell backwards on a feather when this is done, the effect of the hambed. 3. In imitation of Firmus, he laid mering is nothing. If the anvil were & himself down on the ground, and when thin piece of iron, or even two or three an anvil was placed upon his breast, a times heavier than the hammer, the perman hammered with all his forcé a former would be killed by a few blows; piece of iron, with a sledge-hammer, but the blows are scarcely felt when the and sometimes two smiths cut in two anvil is very heavy, for the more matter with chisels a great cold bar of iron laid the anvil has, the greater is its inertia, upon the anvil. At other times, a stone and it is the less liable to be struck out of of huge dimensions was laid upon his its place; for when it has received by the helly, and broken with a blow of the great blow the whole momentum of the hamhammer. 4. The performer then placed mer, its velocity will be so much less his shoulders upon one chair, and his than that of the hammer as its quantity beels upon another, forming with his of matter is greater. When the blow, inback-bone, thighs and legs, an arch. One deed, is struck, the man feels less of or two men then stood upon his belly, the weight of the anvil than he did be