Leonardo Da Vinci as a pioneer in science Part Two Essay Example For Students

Leonardo Da Vinci as a pioneer in science Part Two Essay Leonardo flourished in a period of transition when mediaeval weapons were being replaced by modern fire-arms. The tremendous military value of gunpowder, after its discovery by Roger Bacon in the middle of the thirteenth century, had not quickly been perceived. Cannon were used, it is true, at the battle of Crecy, in 1346; but their general adoption can hardly be dated earlier than the last quarter of the fifteenth century, when they were used by the Spaniards in the conquest of Granada, by Louis XI. in his wars with the great French feudatories, and by the Italian mercenaries in their sordid, dilatory campaigns. So among Leonardo’s inventions we find some which were improvements on the pikes, cross-bows, and catapults of the earlier system, and others which, adapted to the use of gunpowder, extended the scope of the new system. He designed a huge machine, to be worked by ten men in treadmill fashion, from which a large and almost simultaneous volley of shafts could be dischar ged—a forerunner of the Gatling gun and the mitrailleuse. He also planned great catapults, and an enormous copper cannon, which he called Architonitros, to be exploded by steam. He  ascertained that cannon-balls have a velocity of one hundred and ten metres per second, and that it is useless to increase the charge of powder, unless the size of the grain be increased. He experi- mented with fusees ; he devised methods for strengthening fortifications by artillery, and for making ravelins, mines, and storming machines. Just how far he advanced the art of fortification cannot be determined, for we cannot tell how much Vauban invented him- self, and how much he borrowed from the Italian military engineers who preceded him, among whom Leonardo stands foremost. The very important principle of clearance fire, often credited to the Frenchman, appears to have been understood by his Florentine predecessor. Certainly, Leonardo made drawings of what are apparently breech-loading guns. He computed the relative speed and efficacy of stone and lead balls, and suggested that they be conical instead of round. In marine warfare and in navigation he designed improvements. He mentions the log for showing a ship’s progress at sea ; hitherto, the earliest reference to the log was made by Magellan in 1521. He invented swimming-belts, and, more important still, paddle-wheels by which boats might be propelled against wind or current. A century before Stevinus, Leonardo pointed out the need of a rational treatment of mechanical problems ; possibly he suspected the uniformity of mechanical laws. He found the centre of gravity of a pyramid ; he explained the theory of the inclined plane ; he studied the phenomena of concussion, of friction, of the resistance of springs. He invented a dynamometer. Some of his axioms deserve to be cited, for comparison with those now held to be true : â€Å"Percussion,† he says, â€Å"is power reduced into a little time,† and â€Å"exceeds, in equal time, every other natural force†; â€Å"An object which falls freely, acquires in every degree of its descent degrees of velocity;’’ â€Å"A man walking goes faster with his head than with his feet â€Å"That body will become lighter which occupies more air ;† â€Å" No dead object moves by itself, but by another is its motion caused ;† â€Å" No moving object will ever move faster than t he force which moves it;† â€Å"Every action is the result of motion.† In his experiments he used elastic balls suspended by threads, a device  adopted by Borelli and later physicists. He was aware that a body can be under the influence of more than one motive force at the same time. In his researches in attrition and friction he anticipated L’Amoutons (1699), Bulfinger (1727), and Desaguliers (1832). Although his notes on this subject are scanty we infer that he gave attention to electricity. According to Libri,* he first remarked the regular movement of dust placed on elastic surfaces in vibra- tion. Like the inventors of our own times, he aimed at substituting a machine for a man, wherever this substitution would save labor. That he was the first to employ the plus and minus symbols, is an assertion I am unable to verify. Coming next to botany we find that Leonardo’s priority in several important discoveries has been recently established. G. UzielliJ traces the advance he made in three directions, as follows : First, Leonardo discovered the laws of phyllotaxis, or the arrangement of leaves on their stem. He was the first to observe that the order of growth in plants and trees of the same species is uniform, and that their leaves have three different modes of distribution : they may be placed opposite to each other; they may be whorled, or verticillate ; they may be alternate, or spiral. He demonstrated that when leaves grow in pairs they have generally a decussate arrangement, that is, each pair is at right angles to the pair di- rectly above or below it ; and he also showed that when leaves are verticillate, those in one whorl are seldom in a direct line with the whorls above and below. He noted that the quincuncial form is common in the spiral arrangement, the cycle being completed by five le aves, and the sixth leaf being in a direct line with the corresponding leaf above and beneath. â€Å" Since branches grow from buds generated in the axils of leaves,† he said, â€Å"the arrangement of branches on the trunk necessarily corresponds to that of the leaves on the stem.† To Sir Thomas Browne, whose book, â€Å"The Garden  Cyrus, or the Quincuncial Lozenge,† was printed in 1658, the merit of this observation has been hitherto attributed. Second, Leonardo discovered that the age of exogenous trees can be determined from the structure of their trunks. He writes : â€Å"The southern part of the plant shows more vigor and youth than the northern. The rings of the branches of trees show how many years they have lived, and their greater or smaller size whether they were damper or drier. They also show the direction in which they were turned, because they are larger on the north side than on the south, and for this reason the centre of the tree is nearer the bark on the south than on the north side.† Malpighi and Grew (whose works appeared in 1675 and 1682 respectively) have heretofore enjoyed the honor of this discovery. But Montaigne mentions (in his â€Å"Journey into Italy,† July 8, 1581) that at Pisa he bought severalcuriosities, and that â€Å"the person of whom I bought these things, a man of great note as a mathematical instrument maker, told me that trees have all within them as many rings and circle s as they number years. He showed me examples of this in every kind of wood in his shop, for he is a turner by trade. Those trees in a forest which look northwards have these rings closer and thicker than the trees which stand in other directions; and this person told me that this was so invariably the case that by looking at a piece of timber, he could tell how old the tree was, whence it came, and in what direction it had stood.† Montaigne’s â€Å"Journal† was recovered only towards the end of the eighteenth century, so that Malpighi and Grew could not have borrowed from it, but it seems probable that the facts he mentions as having been disclosed to him by the Pisan turner, may have been generally known in the seventeenth century. Third, Leonardo investigated the process of growth in exogenous stems by the formation of new wood on the bark, a process he describes thus: â€Å"The growth in the size of plants is produced by the sap, which is generated in the month of April between the outside coating {camisid) and the wood of the tree. At the same time this outside coating beco mes converted into bark, and the bark acquires new crevices of the depth of ordinary crevices.† This explanation is, I believe, no longer accepted by botanists ; but, though  Leonardos conclusion was inaccurate, his researches must have contributed to the discovery of the truth. He made many drawings of leaves, which for exactness and beauty have never been surpassed. * He also pursued other, more fanciful, experiments, as, for instance, one for testing the effects of poison on trees, by boring a hole in the trunk and injecting arsenic, or sublimate, in alcohol. And he described how an impression of leaves may be had by smearing them with white lead, oil, and lamp-black—as ink is spread on the types — and stamping them on paper: a process which, somewhat modi- fied, has recently been used with success by Hauer and others. That he was a close observer of outward nature, his paintings and drawings of landscape abundantly testify; but he went deeper than the surface, and foresaw more than one vital fact which geologists have since established. Fossils, he maintained, are the remains of plants and animals of a bygone age, and not, as was commonly asserted by his contemporaries, mere â€Å"freaks of nature.† When fossil shells were still in the sea, he affirmed, river-mud near the coast had penetrated into them. â€Å"They tell us that these shells were formed in the hills by the influence of the stars; but I ask, where in the hills are the stars now forming shells of distinct ages and species? and how can the stars explain the origin of gravel, occurring at different heights and composed of pebbles rounded as if by the motion of running water; or in what manner can such a cause ac- count for the petrifaction in the same place of various leaves, seaweeds, and marine crabs ?† In thus proclaimi ng the continuity of geological causes, Leonardo proves his kinship with the masters of modern science. He attributed the denudation of mountain peaks to the gradual subsidence of water, and saw that the direction of a falling body must be affected by the rotation of the earth—an observation which probably explains the following memorandum : â€Å"Write to Bartholomew the Turk about the ebb and flow of the Pontic Sea, and to find out whether a similar phenomenon exits in the Hyrcan, or Caspian Sea.† He held that valleys are the beds of former rivers. His observations of the moon are even more interesting. He it was who, long before Kepler and Galileo, demonstrated that the faint light which we see on the new moon is reflected from the earth.* Kepler, in 1596, and Galileo, a few years previous, pub- lished their explanation of this phenomenon. Leonardo believed that the solar light is radiated to the moon from those parts of the earth where there is most water: â€Å"The water which clothes a large portion of the earth receives on its surface the image of the sun, and with this shines upon the universe and becomes a star with the same splendor which makes us see the other stars.† He also stated that â€Å" the moon has each month a winter and a summer, and has greater heat and cold, and her equinoxes are colder than ours.† To a lunar inhabitant, he said, the earth performs an office like that which the moon performs for us by night. Although the Ptolemaic system still commonly obtained—the terrestrial explorations of Columbus, and the celestial explorations of Copernicus having as yet aroused the suspicion in only a few alert minds that Ptolemy’s doctrine rested on a fallacy—Leonardo maintained that the earth is round, and showed that at a distance of fourteen miles at sea, a man’s body is hidden, owing to the earth’s curving surface ; the distance is incor- rect, but the fact of sphericity has long been undisputed. Still more daring appears his assertion that â€Å"the earth is not situated in the middle of the sun’s orbit, still less at the centre of the universe,† when we remember that the Church persecuted more than one man of science for hazarding this assertion, and that even to-day, the majority of otherwise intelligent persons, are unwilling to r elinquish the flattering tradition which ascribes pre-eminent importance to our planet, and to ourselves as its inhabitants. Computer Science As A Career EssayBy studying echoes he concluded that sound requires a constant time to traverse a given distance. â€Å"It is possible to know by the ear the distance of thunder,† he said, â€Å"if we have first seen the lightning, by analogy with the echo.† He recognised that the action of wind interferes with the velocity of sound. Here is one of his experiments : â€Å"A blow given to a bell corresponds with and will communicate motion to an- other and similar bell; the string of a lute being struck will reply and give motion to a string of similar tone in another lute; and this can be rendered visible by placing a straw upon the string of the second lute.† Of another acoustical problem he said : â€Å" Is the sound in the hammer or in the anvil ? I say : seeing that the anvil is not sus- pended it cannot resound ; but the hammer resounds from the leap it makes just after the blow; and were the anvil to resound . just as a bell, no matter by what material it be struck, yields the same depth of tone, so would the anvil, struck by no matter what hammer. If, therefore, you hear various sounds from hammers of various sizes, the sound proceeds from the hammer and not from the anvil.† Among what we may call the vagaries of Leonardo’s scientific and inventive curiosity, we may mention designs for flying-ships, flying-men, and aerial chairs: but, should the secret of flight ever be discovered, and adapted to general use, it may turn out that his experiments were not so fantastic as they now appear. So, too, of his proposition to walk with wooden shoes on the water. In his youth he was fascinated by that chimera—perpetual motion—which still had a potent charm for investigators. But experience taught him wisdom and he called â€Å"sophistical† the arguments of those who were deluded as he had been. â€Å"It is impossible,† he said, â€Å"to create by any instrument a movement of water from below to above, by means of the descent of which it shall be possible to raise a sim- ilar weight of water to the height from which this descended.† When we remember that four hundred years ago alchemy had not developed into the science of chemistry, nor astrology into astronomy, and that fact and superstition had parted company in but few minds, we shall realise more adequately the vigorous independence of Leonardo, who boldly cast off authority, and chose reason and nature as his guides. He not only called â€Å"sophistical† the attempt to demonstrate perpetual motion, and ridiculed those who wasted their time in trying to square the circle, but he also denounced alchemists as â€Å"liars.† He, too, turned his insatiable curiosity to fantastic experiments, in order to make sure that he had overlooked no possible entrance into the mystery of the universe ; but here, as elsewhere, he was deceived by no hallucinations, and accepted or rejected the products of his researches according to the sole standard of reason. He insists, in his â€Å"Treatise on Painting,† on the infallibility of nature, â€Å"the mistr ess of masters.† â€Å"A pain- ter,† he says, â€Å"ought never to imitate the manner of any other ; because in that case he cannot be called the child, but the grandchild, of nature. It is always better to have recourse to nature, who is re- plete with just abundance of objects, than to the productions of other masters, who learnt everything from her. To her, therefore, he went in quest of scientific truth. He practised, a century before  Bacon, that inductive method which now obtains among all men of science. He preached the need of experiments. â€Å"Experience never deceives, but our judgments are deceived,† is one of his maxims. â€Å" If then you ask me,† he says, â€Å" ‘What fruit do your rules yield, or for what are they good?’ I reply that they bridle investigators, and prevent them from promising impossibilities to themselves and others, and from being rated as fools or cheats.† Four hundred years ago Leonardo rebuked spi ritualistic frauds in this calm fashion : â€Å" There cannot be a voice where there is not motion and percussion of air : there cannot be a percussion of this air where there is no instrument; there can be no incorporeal instru- ment. This being so, a spirit can have neither voice, nor form, nor force, and if it takes body, it cannot penetrate nor enter where the doors are locked. And if any one should say through air collected and packed together spirit takes bodies of various forms, and through that means speaks and moves forcibly, to him I reply that where there are not nerves and bones force cannot be exercised in any motion caused by the pretended spirits.† Such is the epitome of Leonardo’s discoveries—an epitome compiled almost wholly from the reports of those who have edited one volume alone of his autograph memoranda. A strange fatality has followed those manuscripts of his. At his death, he bequeathed them to his pupil Francesco Melzi, who took them back from France to Milan. There they were soon scattered, and no one could deci- pher them ; for Leonardo wrote backwards, from right to left. It was supposed that he used a secret script, and for three hundred years nobody succeeded in reading it. When Napoleon invaded Italy he carried fourteen of these folio volumes to Paris, where they still remain. Others, including many drawings, are in England. One volume, the so-called â€Å"Codice Atlantico,† is preserved at Mi- lan ; it alone has been carefully studied, and in part transcribed and photographed. What rich ore lies buried in the thousands of pages still unedited, may be inferred from what has already been bro ught to light. To the accident of handwriting is due the long ignorance of the world of Leonardo’s attainments in science and discovery. Generations of investigators, unaware of his work, gradually explored the fields which he had traversed, and when at length his memoranda were deciphered, science had in many directions passed beyond him. Later men had the credit of his forgotten discoveries. But the inventory of those discoveries suffices to establish his claim to rank among the supreme men of science of all time. Whatever may be the relative worth of any one of his investigations, there can be no dispute as to the absolute quality of his mind. His methods are the methods of experiment and observation by which man advances victoriously into the mystery which wraps him round. Leonardo’s contemporaries were unprepared to appreciate his scientific accomplishment. Even recent critics have deplored that one who had only four or five peers in art should waste his time in scientific inquiries. He lived so near to the mediaeval superstition that his insight was mistaken for wizardry, and his researches into the properties of matter seemed whimsical or perverse. Doubtless, the incompleteness and multitude of his investigations hindered other men from understanding their importance. He did not publish his discoveries ; he did not even arrange them in formal order for demonstration. Those many thick volumes are but note-books in which he jotted down day by day the experiments he was making, or the conclusions and axioms he had reached, in many subjects. At the outset, he probably intended to collect and classify these vari- ous memoranda in separate treatises, but the revelations came so fast that he had barely time to record them. Had Adam been created at night, imagine with what astonish- ment he must have beheld the first faint dappling of dawn ! How his wonder must have grown as the East became rosy, and the sun rolled above the horizon, and from some unseen source light was poured through the heavens and flooded the earth ! Forms and then colors emerged from the darkness; sounds—of birds, of lisping foliage, the hum of insects, the ripple of brook, or quieter lapping of stream-emerged from the silence. With what delight, with what unworn curiosity must Adam have wandered amid this pageant and listened to this music: everything a miracle, untarnished by the  touch of any yesterdays ; himself unconscious of time or bound, the personification of instant and immeasurable wonder. To Leonardo the world unfolded itself in almost equal fresh- ness, as it would to all of us if custom did not dull our perception. It was, indeed, a new world ! The mediaeval has looked and seen only the handiwork of Satan,—a chaos from which issued spasmodic miracles and caprice—a prison, in which the soul was detained for a few mortal years before it flew heavenwards. Leonardo looked upon this world and saw in it a divine creation, a cosmos of law, a home every nook of which had revelations for the soul. Like the Scandinavian god who could hear the grass grow, his senses were preternaturally keen. He penetrated the cuticle of things ; nature lay transparent to his gaze. He saw the ebb-and-flow of cause and effect. In the least phenomenon he discerned the principle linking it to a class ; in every object, in every creature he beheld the end of a clew which led back and up to the infinite. Thus almost at the beginning of the new age, he was the man whom Nature took into her confidence. To him she granted an apocalyptic vision of her secrets. Subsequent investigators have gone farther. Every acre of the domain of science whose hither boundaries he explored, is now occupied by a specialist. But none has surpassed him in the highest qualities of a man of science—patience to analyse special facts without prejudice, and power to deduce general laws after having accumulated sufficient information. His were the qualities and the methods by which alone mankind are slowly rationalising the world in which we live. Less than any other man who died before our century would he be surprised at the advance in science and at the mechanical inventions of which we boast; for he had, what many men think they have, but have not, a vivid sense of the infinitude of the natural world and of the incalculable possibilities of human achievement. â€Å" What is that,† he asks, â€Å"which does not give itself to human comprehension, and which, if it did, would not exist? It is the infinite, which, if it could so give itself, would b e done and ended.