Imágenes de páginas
PDF
EPUB

D

[ocr errors]

that one, when put into the water, sinks the walnut-tree is less than the ebony's to the bottom, and that the other stays force for going to the bottom." to swim at the top; and the matter “Now, let us return to the thin plate of being the same, and the two bodies dif- gold or silver, or the thin board of ebony, fering in nothing but in figure, they and let us lay it lightly upon the water, so affirm that with all perspicuity they that it may stay there without sinking, have demonstrated and sensibly manis and carefully observe the effect. It will fested what they undertook. Neverthe- appear clearly that the plates are a consiless I believe, and think I can prove derable matter lower than the surface of that this very experiment proves nothing the water which rises up, and makes a against my theory.

And first it is kind of rampart round them on every false that the ball sinks, and the board side, in the manner shewn in the annot; for the board will sink too, if you nexed figure, in which BD L F repredo to both the figures as the words of

В: our question require; that is, if you put them both in the water; for to be in the water implies to be placed in the water, and by Aristotle's own definition of place, to be placed imports to be en

E vironed by the surface of the ambient body; but when my antagonists shew the floating board of ebony, they put it sents the surface of the water, and not into the water, but upon the water;' AEIO the surface of the plate. But if where, being detained by a certain im- it have already penetrated and overcome pediment (of which more anon) it is sur- the continuity of the water, and is of its rounded, partly with water, partly with own nature heavier than the water, why air, which is contrary to our agreement, does it not continue to sink, but stop for that was that the bodies should be and suspend itself in that little dimple in the water, and not part in the water, that its weight has made in the water ? part in the air. I will not omit another My answer is, because in sinking till its reason, founded also upon experience, surface is below the water which rises and, if I deceive not myself, conclu- up in a bank round it, it draws after and sive against the notion that figure, and carries along with it the air above it, so the resistance of the water to penetra- that that which in this case descends and tion have anything to do with the buoy, is placed in the water, is not only the ancy of bodies. Choose a piece of wood board of ebony or plate of iron, but a or other matter, as for instance walnut- compound of ebony and air, from which wood, of which a ball rises from the composition results a solid no longer bottom of the water to the surface more specifically heavier than the water, as was slowly than a ball of ebony of the same the ebony or gold alone. But, Gentlemen, size sinks, so that clearly the ball of we want the same matter; you are to ebony divides the water more readily in alter nothing but the shape, and theresinking than does the walnut in rising; fore have the goodness to remove this Then take a board of walnut-tree equal air, which may be done simply by washto and like the floating ebony one of ing the upper surface of the board, for my antagonists; and if it be true that the water having once got between the this latter floats by reason of the figure board and air will run together, and the being unable to penetrate the water, the ebony will go to the bottom; and if it other of walnut-tree, withont all ques. does not, you have won the day. But tion, if thrust to the bottom ought to methinks I hear some of my antagonists stay there, as having the same impeding cunningly opposing this, and telling me figure, and being less apt to overcome that they will not on any account allow the said resistance of the water. But if their board to be wetted, because the we find by experience that not only the weight of the water so added, by making thin board, but every other figure of the it heavier than it was before, draws it to same walnut-tree will return to Aoat, as the bottom, and that the addition of new unquestionably we shall, then I must weight is contrary to our agreement, desire my opponents to forbear to attri- which was that the matter should be the bute the floating of the ebony to the same.” figure of the board, since the resistance “ To this I answer first, that nobody of the water is the same in rising as in can suppose bodies to be put into the sinking, and the force of ascension of water without their being wet, nor do I Having

wish to do more to the board than you quite smooth and even. This, if put may do to the ball. Moreover, it is not gently into the water, submerges almost true that the board sinks on account of entirely, there remaining visible only a the weight of the water added in the little of the very top, which, so long as washing; for I will put ten or twenty it is joined to the air, keeps the ball drops on the floating board, and so long afloat; but if we take away the contact as they stand separate it shall not sink; of the air by wetting this top, the ball but if the board be taken out, and all sinks to the bottom, and remains there. that water wiped off, and the whole sur- Now to make it return to the surface face bathed with one single drop, and by virtue of the air which before susput it again upon the water, there is no tained it, thrust into the water a glass, question but it will sink, the other water with the mouth downwards, which will running to cover it, being no longer carry with it the air it contains; and hindered by the air. In the next place move this down towards the ball, until it is altogether false that water can in you see by the transparency of the glass any way increase the weight of bodies that the air has reached the top of it; immersed in it, for water has no weight then gently draw the glass upwards, and in water, since it does not sink. Now, you will see the ball rise, and afterwards just as he who should say that brass stay on the top of the water, if you careby its own nature sinks, but that when fully part the glass and water without formed into the shape of a kettle, it ac- too much disturbing it*. There is quires from that figure a virtue of lying therefore a certain affinity between the in the water without sinking, would say air and other bodies, which holds them what is false, because that is not purely united, so that they separate not without brass which then is put into the water, a kind of violence, just as between water but a compound of brass and air; so is and other bodies; for in drawing them it neither more nor less false, that a thin wholly out of the water, we see the water plate of brass or ebony swims by virtue follow them, and rise sensibly above the of its dilated and broad figure. Also I level before it quits them.” cannot omit to tell my opponents, that established this principle by this exceedthis conceit of refusing to bathe the sur- ingly ingenious and convincing experiface of the board, might beget an opinion ment, Galileo proceeds to shew from it in a third person of a poverty of argu- what must be the dimensions of a plate ments on their side, especially as the of any substance which will float as the conversation began about flakes of ice, wax does, assuming in each case that in which it would be simple to require we know the greatest height at which that the surfaces should be kept dry; the rampart of water will stand round not to mention that such pieces of ice, it. In like manner he shows that a pywhether wet or dry, always float, and ramidal or conical figure may be made as my antagonists say, because of their of any substance, such that by help of shape."

the air, it shall rest upon the water with“Some may wonder that I affirm this out wetting more than its base; and power to be in the air of keeping the that we may so form a cone of any subplate of brass or silver above water, as stance that it shall float if placed gently if in a certain sense I would attribute to on the surface, with its point downwards, the air a kind of magnetic virtue for sus- whereas no care or pains will enable it taining heavy bodies with which it is to float with its base downwards, owing in contact. To satisfy all these doubts, to the different proportions of air which I have contrived the following experi- in the two positions remain connected ment to demonstrate how truly the air with it. With this parting blow at his does support these solids; for I have antagonist's theory we close our exfound, when one of these bodies which tracts from this admirable essay. floats when placed lightly on the water, The first elements of the theory of is thoroughly bathed and sunk to the running waters were reserved for Castelli, bottom, that by carrying down to it a an intimate friend and pupil of Galileo. little air without otherwise touching it on the present occasion, Castelli apin the least, I am able to raise and carry peared as the ostensible author of a deit back to the top, where it floats as before. To this effect I take a ball of

• In making this very beautisul experiment, it is wax, and with a little lead make it just best to keep the glass a few seconds in the water, to heavy enough to sink very slowly to the give time for the surface of the ball to dry. It will

also succeed with a light needle, if carefully conbottom, taking care that its surface be

ducted.

fence against the attacks made by Vin- non, although it is admirable to see cenzio di Grazia and by Lodovico delle the contempt with which, even in that Columbe (the author of the crystalline trying moment, he expresses his concomposition of the moon) on the ob- sciousness that his adversaries were noxious theory. After destroying all the unworthy of the triumph they appeared objections which they produced, the on the point of celebrating.--"Looking writer tauntingly bids them remember, on Saturn within these few days, I found that he was merely Galileo's pupil, and it solitary, without the assistance of its consider how much more effectually accustomed stars, and in short, perGalileo himself would have confuted fectly round and defined like Jupiter, and them, had he thought it worth while. It such it still remains. Now what can was not known till several years after be said of so strange a metamorphosis ? his death, that this Essay was in fact are perhaps the two smaller stars conwritten by Galileo himself.*

sumed, like the spots on the sun ? have These compositions merely occupied they suddenly vanished and fled ? or has the leisure time which he could withhold Saturn devoured his own children? or from the controversy on the solar spots was the appearance indeed fraud and to which we have already alluded. A illusion, with which the glasses have for German Jesuit named Christopher so long a time mocked me, and so many Scheiner, who was professor of mathe- others who have often observed with me. matics at Ingolstadt, in imitation of Ga- Now perhaps the time is come to revive lileo had commenced a series of obser- the withering hopes of those, who, guided vations on them, but adopted the theory by more profound contemplations, have which, as we have seen, Galileo had exa- fathomed all the fallacies of the new obmined and rejected, that these spots are servations and recognised their impossiplanets circulating at some distance from bility! I cannot resolve what to say in the body of the sun. The same opinion a chance so strange, so new, and so unhad been taken up by a French astrono expected; the shortness of the time, the mer, who in honour of the reigning fa- unexampled occurrence, the weakness of mily called them Borbonian stars. my intellect, and the terror of being misScheiner promulgated his notions in taken, have greatly confounded me." three letters, addressed to their common These first expressions of alarm are not friend Welser, under the quaint signature to be wondered at; however, he soon of“ Apelles latens post tabulam." Galileo recovered courage, and ventured to forereplied to Scheiner's letters by three tel the periods at which the lateral stars others, also addressed to Welser, and would again show themselves, protestalthough the dispute was carried on amid ing at the same time, that he was in no mutual professions of respect and es- respect to be understood as classing this teem, it laid the foundation of the total prediction among the results which deestrangement which afterwards took pend on certain principles and sound place between the two authors. Galileo's conclusions, but merely on some conjecpart of this controversy was published tures which appeared to him probable. at Rome by the Lyncean Academy in From one of the Dialogues on the Sys1613. To the lasť of his letters, writ- tem, we learn that this conjecture was, ten in December, 1612, is annexed a that Saturn might revolve upon his axis, table of the expected positions of Ju- but the period which he assumed is very piter's satellites during the months of different from the true one, as might be March and April of the following year, expected from its being intended to acwhich, imperfect as it necessarily was, count for a phenomenon of which Galileo cannot be looked upon without the had not rightly apprehended the chagreatest interest.

racter. In the same letter it is mentioned that He closed this letter with renewed Saturn presented a novel appearance, professions of courtesy and friendship which, for an instant, almost induced towards Apelles, enjoining Welser not Galileo to mistrust the accuracy of his to communicate it without adding his earlier observations. The lateral ap- excuses, if he should be thought to dispendages of this planet had disappeared, sent too violently from his antagonist's and the accompanying extract will show ideas, declaring that his only object was the uneasiness which Galileo could not the discovery of truth, and that he had conceal at the sight of this phenome- freely exposed his own opinion, which he

was still ready to change, so soon as his • Nelli, Saggio di Stor. Liter. Fiorent, errors should be made manifest to him; and that he would consider himself under pressions contained in the Scriptures, special obligation to any one who would and asserted, that the object of the Scrip be kind enough to discover and correct tures not being to teach astronomy, such them. These letters were written from expressions are there used as would be the villa of his friend Salviati at Selve intelligible and conformable to the vulgar near Florence, where he passed great belief, without regard to the true strucpart of his time, particularly during his ture of the universe ; which argument frequent indispositions, conceiving that he afterwards amplified in a letter ada the air of Florence was prejudicial to him. dressed to Christina, Grand Duchess of Cesi was very anxious for their appear- Tuscany, the mother of his patron ance, since they were in his own words) Cosmo. He discourses on this subject so hard a morsel for the teeth of the with the moderation and good sense Peripatetics, and he exhorted Galileo, in which so peculiarly characterized him. the name of the society, " to continue “I am,” says he, "inclined to believe, to give them, and the nameless Jesuit, that the intention of the sacred Scriptures something to gnaw."

is to give to mankind the information

necessary for their salvation, and which, CHAPTER XI.

surpassing all human knowledge, can by Letter to Christina, Arch-Duchess of no other means be accredited than by

Tuscany-Caccini - Galileo revisits the mouth of the Holy Spirit. But I do Rome— Inchoffer Problem of Lon- not hold it necessary to believe, that the gitudes.

same God who has endowed us with

senses, with speech, and intellect, inThe uncompromising boldness with tended that we should neglect the use of which Galileo published and supported these, and seek by other means for his opinions, with little regard to the knowledge which they are sufficient to power and authority of those who ad- procure us; especially in a science like vocated the contrary doctrines, had astronomy, of which so little notice is raised against him a host of enemies, taken in the Scriptures, that none of the who each had objections to him peculiar planets, except the sun and moon, and, to themselves, but who now began to once or twice only, Venus under the perceive the policy of uniting their name of Lucifer, are so much as named strength in the common cause, to crush there. This therefore being granted, if possible so dangerous an innovator. methinks that in the discussion of natural All the professors of the old opinions, problems we ought not to begin at the who suddenly found the knowledge on authority of texts of Scripture, but at which their reputation was founded sensible experiments and necessary destruck from under them, and who could monstrations : for, from the divine word, not reconcile themselves to their new the sacred Scripture and nature did situation of learners, were united against both alike proceed, and I conceive that, him ; and to this powerful cabal was concerning natural effects, that which now added the still greater influence of either sensible experience sets before the jesuits and pseudo-theological party, our eyes, or necessary demonstrations do who fancied they saw in the spirit of prove unto us, ought not upon any acGalileo's writings the same inquisitive count to be called into question, much temper which they had already found less condemned, upon the testimony of so inconvenient in Luther and his ad- Scriptural texts, which may under their herents. The alarm became greater words couch senses seemingly contrary every day, inasmuch as Galileo had thereto. succeeded in training round him a nu- ** Again, to command the very promerous band of followers who all ap- fessors of astronomy that they of thempeared imbued with the same dangerous selves see to the confuting of their own spirit of innovation, and his favourite observations and demonstrations, is to scholars were successful candidates for enjoin a thing beyond all possibility of professorships in many of the most cele- doing ; for it is not only to command brated universities of Italy.

them not to see that which they do see, At the close of 1613, Galileo addressed and not to understand that which they a letter to his pupil, the Abbé Castelli, do understand, but it is to order them to in which he endeavoured to shew that seek for and to find the contrary of that there is as much difficulty in reconciling which they happen to meet with. I would the Ptolemaic as the Copernican system entreat these wise and prudent fathers, of the world with the astronomical ex-' that they would with all diligence consider the difference that is between opinion- pulpit, by a Dominican friar named ative and demonstrative doctrines: to Caccini, who thought it not unbecoming the end that well weighing in their minds his habit or religion to play upon the with what force necessary inferences urge words of a Scriptural text for the purus, they might the better assure them- pose of attacking Galileo and his partiselves that it is not in the power of the sans with more personality*. Galileo professors of demonstrative sciences to complained formally of Caccini's conchange their opinions at pleasure, and duct to Luigi Maraffi the general of the adopt first one side and then another; Dominicans, who apologised amply to and that there is a great difference be him, adding that he himself was to be tween commanding a mathematician or pitied for finding himself implicated in a philosopher, and the disposing of a all the brutal conduct of thirty or forty lawyer or a merchant; and that the thousand monks. demonstrated conclusions touching the In the mean time, the inquisitors at things of nature and of the heavens can- Rome had taken the alarm, and were not be changed with the same facility already, in 1615, busily employed in colas the opinions are touching what is lecting evidence against Galileo. Lorini, lawful or not in a contract, bargain, or a brother Dominican of Caccini, had bill of exchange. Therefore, first let given them notice of the letter to Casthese men apply themselves to examine telli of which we have spoken, and the the arguments of Copernicus and others, utmost address was employed to get the and leave the condemning of them as original into their hands, which attempt erroneous and heretical to whom it be- however was frustrated, as Castelli had longeth; yet let them not hope to find returned it to the writer.

Caccini was such rash and precipitous determinations sent for to Rome, settled there with the in the wary and holy fathers, or in the title of Master of the Convent of St. absolute wisdom of him who cannot err, Mary of Minerva, and employed to put as those into which they suffer them- the depositions against Galileo into selves to be hurried by some particular order. Galileo was not at this time affection or interest of their own. In fully aware of the machinations against these and such other positions, which him, but suspecting something of their are not directly articles of faith, certainly nature, he solicited and obtained perno man doubts but His Holiness hath mission from Cosmo, towards the end of always an absolute power of admitting 1615, to make a journey to Rome, for or condemning them, but it is not in the purpose of more directly confronting the power of any creature to make them his enemies in that city. There was a to be true or false, otherwise than of rumour at the time that this visit was their own nature, and in fact they are.” not voluntary, but that Galileo had been We have been more particular in ex- cited to appear at Rome. A contempotracting these passages, because it has rary declares that he heard this from been advanced by a writer of high re- Galileo himself: at any rate, in a letter putation, that the treatment which which Galileo shortly afterwards wrote Galileo subsequently experienced was to Picchena, the Grand Duke's secresolely in consequence of his persisting in tary, he expresses himself well satisfied the endeavour to prove that the Scrip with the results of this step, whether tures were reconcileable with the Co- forced or not, and Querenghi thus depernican theory*, whereas we see here scribes to the Cardinal d'Este the public distinctly that, for the reasons we have effect of his appearance : “ Your Emibriefly stated, he regarded this as a nence would be delighted with Galileo if matter altogether indifferent and beside you heard him holding forth, as he often the question.

does, in the midst of fifteen or twenty, Galileo' had not entered upon this all violently attacking him, sometimes in discussion till driven to it by a most one house, sometimes in another. But indecent attack, made on him from the he is armed after such fashion that he

laughs all of them to scorn-and even if * Ce philosophe (Galilée) ne fut point persecute the novelty of his opinions prevents enlogien. C'est son entêtement vouloir concilier la tire persuasion, at least he convicts of Bible avec Copernic qui lui donna des juges. Mais emptiness most of the arguments with vingt auteurs, surtout parmi les protestans, ont écrit que Galilée fut persecuté et imprisonné pour avoir

which his adversaries endeavour to oversontenu que la terre tourne autour du soleil, que ce whelm him. He was particularly admisystème a été condanné par l'inquisition comme faux, erroné et contraire à la Bible, &c.-Bergier, Encyclopédie Methodique, Paris, 1790, Art. SCIENCES * Viri Galilæi, quid statis adspicientes in cælum, HUMAINES,

Acts I. II.

comme bon astronome, mais comme mauvais théo

« AnteriorContinuar »