The Martyrs of Science, or, The lives of Galileo, Tycho Brahe, and Kepler.

by David Brewster.

CHAPTER I.

_Peculiar interest attached to his Life--His Birth--His early studies--His pa.s.sion for Mathematics--His work on the Hydrostatic Balance--Appointed Lecturer on Mathematics at Pisa--His antipathy to the Philosophy of Aristotle--His contentions with the Aristotelians--Chosen professor of Mathematics in Padua--Adopts the Copernican system, but still teaches the Ptolemaic doctrine--His alarming illness--He observes the new Star in 1604--His magnetical experiments._

The history of the life and labours of Galileo is pregnant with a peculiar interest to the general reader, as well as to the philosopher.

His brilliant discoveries, the man of science regards as his peculiar property; the means by which they were made, and the development of his intellectual character, belong to the logician and to the philosopher; but the triumphs and the reverses of his eventful life must be claimed for our common nature, as a source of more than ordinary instruction.

The lengthened career which Providence a.s.signed to Galileo was filled up throughout its rugged outline with events even of dramatic interest. But though it was emblazoned with achievements of transcendent magnitude, yet his n.o.blest discoveries were the derision of his contemporaries, and were even denounced as crimes which merited the vengeance of Heaven.

Though he was the idol of his friends, and the favoured companion of princes, yet he afterwards became the victim of persecution, and spent some of his last hours within the walls of a prison; and though the Almighty granted him, as it were, a new sight to descry unknown worlds in the obscurity of s.p.a.ce, yet the eyes which were allowed to witness such wonders, were themselves doomed to be closed in darkness.

Such were the lights and shadows in which history delineates

"The starry Galileo with his woes."[1]

[1] Childe Harold, canto iv. stanza liv.

But, however powerful be their contrasts, they are not unusual in their proportions. The balance which has been struck between his days of good and evil, is that which regulates the lot of man, whether we study it in the despotic sway of the autocrat, in the peaceful inquiries of the philosopher, or in the humbler toils of ordinary life.

Galileo Galilei was born at Pisa, on the 15th of February, 1564, and was the eldest of a family of three sons and three daughters. Under the name of Bonajuti, his n.o.ble ancestors had filled high offices at Florence; but about the middle of the 14th century they seem to have abandoned this surname for that of Galileo. Vincenzo Galilei, our author's father, was himself a philosopher of no mean powers; and though his talents seem to have been exercised only in the composition of treatises on the theory and practice of music, yet he appears to have antic.i.p.ated even his son in a just estimate of the philosophy of the age, and in a distinct perception of the true method of investigating truth.[2]

[2] Life of Galileo, Library of Useful Knowledge, p. 1.

The early years of Galileo were, like those of almost all great experimental philosophers, spent in the construction of instruments and pieces of machinery, which were calculated chiefly to amuse himself and his schoolfellows. This employment of his hands, however, did not interfere with his regular studies; and though, from the straitened circ.u.mstances of his father, he was educated under considerable disadvantages, yet he acquired the elements of cla.s.sical literature, and was initiated into all the learning of the times. Music, drawing, and painting were the occupations of his leisure hours; and such was his proficiency in these arts, that he was reckoned a skilful performer on several musical instruments, especially the lute; and his knowledge of pictures was held in great esteem by some of the best artists of his day.

Galileo seems to have been desirous of following the profession of a painter: but his father had observed decided indications of early genius; and, though by no means able to afford it, he resolved to send him to the university to pursue the study of medicine. He accordingly enrolled himself as a scholar in arts at the university of Pisa, on the 5th of November, 1581, and pursued his medical studies under the celebrated botanist Andrew Caesalpinus, who filled the chair of medicine from 1567 to 1592.

In order to study the principles of music and drawing, Galileo found it necessary to acquire some knowledge of geometry. His father seems to have foreseen the consequences of following this new pursuit, and though he did not prohibit him from reading Euclid under Ostilio Ricci, one of the professors at Pisa, yet he watched his progress with the utmost jealousy, and had resolved that it should not interfere with his medical studies. The demonstrations, however, of the Greek mathematician had too many charms for the ardent mind of Galileo. His whole attention was engrossed with the new truths which burst upon his understanding; and after many fruitless attempts to check his ardour and direct his thoughts to professional objects, his father was obliged to surrender his parental control, and allow the fullest scope to the genius of his son.

From the elementary works of geometry, Galileo pa.s.sed to the writings of Archimedes; and while he was studying the hydrostatical treatise[3] of the Syracusan philosopher, he wrote his essay on the hydrostatical balance,[4] in which he describes the construction of the instrument, and the method by which Archimedes detected the fraud committed by the jeweller in the composition of Hiero's crown. This work gained for its author the esteem of Guido Ubaldi, who had distinguished himself by his mechanical and mathematical acquirements, and who engaged his young friend to investigate the subject of the centre of gravity in solid bodies. The treatise on this subject, which Galileo presented to his patron, proved the source of his future success in life.

[3] De Insidentibus in Fluido.

[4] Opere di Galileo. Milano, 1810, vol. iv. p. 248-257.

Through the Cardinal del Monte, the brother-in-law of Ubaldi, the reigning Duke of Tuscany, Ferdinand de Medici was made acquainted with the merits of our young philosopher; and, in 1589, he was appointed lecturer on mathematics at Pisa. As the salary, however, attached to this office was only sixty crowns, he was compelled to enlarge this inadequate income by the additional occupation of private teaching, and thus to encroach upon the leisure which he was anxious to devote to science.

With this moderate competency, Galileo commenced his philosophical career. At the early age of eighteen, when he had entered the university, his innate antipathy to the Aristotelian philosophy began to display itself. This feeling was strengthened by his earliest inquiries; and upon his establishment at Pisa he seems to have regarded the doctrines of Aristotle as the intellectual prey which, in his chace of glory, he was destined to pursue. Nizzoli, who flourished near the beginning of the sixteenth century, and Giordano Bruno, who was burned at Rome in 1600, led the way in this daring pursuit; but it was reserved for Galileo to track the Thracian boar through its native thickets, and, at the risk of his own life, to strangle it in its den.

With the resolution of submitting every opinion to the test of experiment, Galileo's first inquiries at Pisa were directed to the mechanical doctrines of Aristotle. Their incorrectness and absurdity soon became apparent; and with a zeal, perhaps, bordering on indiscretion, he denounced them to his pupils with an ardour of manner and of expression proportioned to his own conviction of the truth. The detection of long-established errors is apt to inspire the young philosopher with an exultation which reason condemns. The feeling of triumph is apt to clothe itself in the language of asperity; and the abettor of erroneous opinions is treated as a species of enemy to science. Like the soldier who fleshes his first spear in battle, the philosopher is apt to leave the stain of cruelty on his early achievements. It is only from age and experience, indeed, that we can expect the discretion of valour, whether it is called forth in controversy or in battle. Galileo seems to have waged this stern warfare against the followers of Aristotle; and such was the exasperation which was excited by his reiterated and successful attacks, that he was a.s.sailed, during the rest of his life, with a degree of rancour which seldom originates in a mere difference of opinion. Forgetting that all knowledge is progressive, and that the errors of one generation call forth the comments, and are replaced by the discoveries, of the next, Galileo did not antic.i.p.ate that his own speculations and incompleted labours might one day provoke unmitigated censure; and he therefore failed in making allowance for the prejudices and ignorance of his opponents. He who enjoys the proud lot of taking a position in advance of his age, need not wonder that his less gifted contemporaries are left behind. Men are not necessarily obstinate because they cleave to deeply rooted and venerable errors, nor are they absolutely dull when they are long in understanding and slow in embracing newly discovered truths.

It was one of the axioms of the Aristotelian mechanics, that the heavier of two falling bodies would reach the ground sooner than the other, and that their velocities would be proportional to their weights. Galileo attacked the arguments by which this opinion was supported; and when he found his reasoning ineffectual, he appealed to direct experiment. He maintained, that all bodies would fall through the same height in the same time, if they were not unequally r.e.t.a.r.ded by the resistance of the air: and though he performed the experiment with the most satisfactory results, by letting heavy bodies fall from the leaning tower of Pisa, yet the Aristotelians, who with their own eyes saw the unequal weights strike the ground at the same instant, ascribed the effect to some unknown cause, and preferred the decision of their master to that of nature herself.

Galileo could not brook this opposition to his discoveries; nor could the Aristotelians tolerate the rebukes of their young instructor. The two parties were, consequently, marshalled in hostile array; when, fortunately for both, an event occurred, which placed them beyond the reach of danger. Don Giovanni de Medici, a natural son of Cosmo, had proposed a method of clearing out the harbour of Leghorn. Galileo, whose opinion was requested, gave such an unfavourable report upon it, that the disappointed inventor directed against him all the force of his malice. It was an easy task to concentrate the malignity of his enemies at Pisa; and so effectually was this accomplished, that Galileo resolved to accept another professorship, to which he had been previously invited.

The chair of mathematics in the university of Padua having been vacant for five years, the republic of Venice had resolved to fill it up; and, on the recommendation of Guido Ubaldi, Galileo was appointed to it, in 1592, for a period of six years.

Previous to this event, Galileo had lost his father, who died, in 1591, at an advanced age. As he was the eldest son, the support of the family naturally devolved upon him; and this sacred obligation must have increased his anxiety to better his circ.u.mstances, and therefore added to his other inducements to quit Pisa. In September 1592, he removed to Padua, where he had a salary of only 180 florins, and where he was again obliged to add to his income by the labours of tuition. Notwithstanding this fruitless occupation of his time, he appears to have found leisure for composing several of his works, and completing various inventions, which will be afterwards described. His ma.n.u.scripts were circulated privately among his friends and pupils; but some of them strayed beyond this sacred limit, and found their way into the hands of persons, who did not scruple to claim and publish, as their own, the discoveries and inventions which they contained.

It is not easy to ascertain the exact time when Galileo became a convert to the doctrines of Copernicus, or the particular circ.u.mstances under which he was led to adopt them. It is stated by Gerard Voss, that a public lecture of Moestlin, the instructor of Kepler, was the means of making Galileo acquainted with the true system of the universe. This a.s.sertion, however, is by no means probable; and it has been ably shown, by the latest biographer of Galileo,[5] that, in his dialogues on the Copernican system, our author gives the true account of his own conversion. This pa.s.sage is so interesting, that we shall give it entire.

[5] Life of Galileo, in Library of Useful Knowledge, p. 9.

"I cannot omit this opportunity of relating to you what happened to myself at the time when this opinion (the Copernican system) began to be discussed. I was then a very young man, and had scarcely finished my course of philosophy, which other occupations obliged me to leave off, when there arrived in this country, from Rostoch, a foreigner, whose name, I believe, was Christian Vurstisius (Wurteisen), a follower of Copernicus. This person delivered, on this subject, two or three lectures in a certain academy, and to a crowded audience. Believing that several were attracted more by the novelty of the subject than by any other cause, and being firmly persuaded that this opinion was a piece of solemn folly, I was unwilling to be present. Upon interrogating, however, some of those who were there, I found that they all made it a subject of merriment, with the exception of one, who a.s.sured me that it was not a thing wholly ridiculous. As I considered this individual to be both prudent and circ.u.mspect, I repented that I had not attended the lectures; and, whenever I met any of the followers of Copernicus, I began to inquire if they had always been of the same opinion. I found that there was not one of them who did not declare that he had long maintained the very opposite opinions, and had not gone over to the new doctrines till he was driven by the force of argument. I next examined them one by one, to see if they were masters of the arguments on the opposite side; and such was the readiness of their answers, that I was satisfied they had not taken up this opinion from ignorance or vanity.

On the other hand, whenever I interrogated the Peripatetics and the Ptolemeans--and, out of curiosity, I have interrogated not a few--respecting their perusal of Copernicus's work, I perceived that there were few who had seen the book, and not one who understood it. Nor have I omitted to inquire among the followers of the Peripatetic doctrines, if any of them had ever stood on the opposite side; and the result was, that there was not one. Considering, then, that n.o.body followed the Copernican doctrine, who had not previously held the contrary opinion, and who was not well acquainted with the arguments of Aristotle and Ptolemy; while, on the other hand, n.o.body followed Ptolemy and Aristotle, who had before adhered to Copernicus, and had gone over from him into the camp of Aristotle;--weighing, I say, these things, I began to believe that, if any one who rejects an opinion which he has imbibed with his milk, and which has been embraced by an infinite number, shall take up an opinion held only by a few, condemned by all the schools, and really regarded as a great paradox, it cannot be doubted that he must have been induced, not to say driven, to embrace it by the most cogent arguments. On this account I have become very curious to penetrate to the very bottom of the subject."[6]

[6] Systema Cosmic.u.m, Dial. ii. p. 121.

It appears, on the testimony of Galileo himself, that he taught the Ptolemaic system, in compliance with the popular feeling, after he had convinced himself of the truth of the Copernican doctrines. In the treatise on the sphere, indeed, which bears his name,[7] and which must have been written soon after he went to Padua, and subsequently to 1592, the stability of the earth, and the motion of the sun, are supported by the very arguments which Galileo afterwards ridiculed; but we have no means of determining whether or not he had then adopted the true system of the universe. Although he might have taught the Ptolemaic system in his lectures after he had convinced himself of its falsehood, yet it is not likely that he would go so far as to publish to the world, as true, the very doctrines which he despised. In a letter to Kepler, dated in 1597, he distinctly states that he _had, many years ago, adopted the opinions of Copernicus_; but that _he had not yet dared to publish his arguments in favour of them, and his refutation of the opposite opinions_. These facts would leave us to place Galileo's conversion somewhere between 1593 and 1597, although _many_ years cannot be said to have elapsed between these two dates.

[7] The authenticity of this work has been doubted. It was printed at Rome, in 1656, from a MS. in the library of Somaschi, at Venice.

See Opere di Galileo, tom. vii. p. 427.

At this early period of Galileo's life, in the year 1593, he met with an accident which had nearly proved fatal. A party at Padua, of which he was one, were enjoying, at an open window, a current of air, which was artificially cooled by a fall of water. Galileo unfortunately fell asleep under its influence; and so powerful was its effect upon his robust const.i.tution, that he contracted a severe chronic disorder, accompanied with acute pains in his body, and loss of sleep and appet.i.te, which attacked him at intervals during the rest of his life.

Others of the party suffered still more severely, and perished by their own rashness.

Galileo's reputation was now widely extended over Europe. The Archduke Ferdinand (afterwards Emperor of Germany), the Landgrave of Hesse, and the Princes of Alsace and Mantua, honoured his lectures with their presence; and Prince Gustavus Adolphus of Sweden also received instructions from him in mathematics, during his sojourn in Italy.

When Galileo had completed the first period of his engagement at Padua, he was re-elected for other six years, with an increased salary of 320 florins. This liberal addition to his income is ascribed by Fabbroni to the malice of one of his enemies, who informed the Senate that Galileo was living in illicit intercourse with Marina Gamba. Without inquiring into the truth of the accusation, the Senate is said to have replied, that if "he had a family to support, he had the more need of an increased salary." It is more likely that the liberality of the republic had been called forth by the high reputation of their professor, and that the terms of their reply were intended only to rebuke the malignity of the informer. The mode of expression would seem to indicate that one or more of Galileo's children had been born previous to his re-election in 1598; but as this is scarcely consistent with other facts, we are disposed to doubt the authenticity of Fabbroni's anecdote.

The new star which attracted the notice of astronomers in 1604, excited the particular attention of Galileo. The observations which he made upon it, and the speculations which they suggested, formed the subject of three lectures, the beginning of the first of which only has reached our times. From the absence of parallax, he proved that the common hypothesis of its being a meteor was erroneous, and that, like the fixed stars, it was situated far beyond the bounds of our own system. The popularity of the subject attracted crowds to his lecture-room; and Galileo had the boldness to reproach his hearers for taking so deep an interest in a temporary phenomenon, while they overlooked the wonders of creation which were daily presented to their view.

In the year 1606, Galileo was again appointed to the professorship at Padua, with an augmented stipend of 520 florins. His popularity had now risen so high, that his audience could not be accommodated in his lecture-room; and even when he had a.s.sembled them in the school of medicine, which contained 1000 persons, he was frequently obliged to adjourn to the open air.

Among the variety of pursuits which occupied his attention, was the examination of the properties of the loadstone. In 1607, he commenced his experiments; but, with the exception of a method of arming loadstones, which, according to the report of Sir Kenelm Digby, enabled them to carry twice as much weight as before, he does not seem to have made any additions to our knowledge of magnetism. He appears to have studied with care the admirable work of our countryman, Dr Gilbert, "De Magnete," which was published in 1600; and he recognised in the experiments and reasonings of the English philosopher the principles of that method of investigating truth which he had himself adopted. Gilbert died in 1603, in the 63d year of his age, and probably never read the fine compliment which was paid to him by the Italian philosopher--"I extremely praise, admire, and envy this author."

CHAPTER II.

_Cosmo, Grand Duke of Tuscany, invites Galileo to Pisa--Galileo visits Venice in 1609, where he first hears of the Telescope--He invents and constructs one, which excites a great sensation--Discovers Mountains in the Moon, and Forty Stars in the Pleiades--Discovers Jupiter's Satellites in 1610--Effect of this discovery on Kepler--Manner in which these discoveries were received--Galileo appointed Mathematician to Cosmo--Mayer claims the discovery of the Satellites of Jupiter--Harriot observes them in England in October 1610._

In the preceding chapter we have brought down the history of Galileo's labours to that auspicious year in which he first directed the telescope to the heavens. No sooner was that n.o.ble instrument placed in his hands, than Providence released him from his professional toils, and supplied him with the fullest leisure and the amplest means for pursuing and completing the grandest discoveries.

Although he had quitted the service and the domains of his munificent patron, the Grand Duke of Tuscany, yet he maintained his connection with the family, by visiting Florence during his academic vacations, and giving mathematical instruction to the younger branches of that distinguished house. Cosmo, who had been one of his pupils, now succeeded his father Ferdinand; and having his mind early imbued with a love of knowledge, which had become hereditary in his family, he felt that the residence of Galileo within his dominions, and still more his introduction into his household, would do honour to their common country, and reflect a l.u.s.tre upon his own name. In the year 1609, accordingly, Cosmo made proposals to Galileo to return to his original situation at Pisa. These overtures were gratefully received; and in the arrangements which Galileo on this occasion suggested, as well as in the manner in which they were urged, we obtain some insight into his temper and character. He informs the correspondent through whom Cosmo's offer was conveyed, that his salary of 520 florins at Padua would be increased to as many crowns at his re-election, and that he could enlarge his income to any extent he pleased, by giving private lectures and receiving pupils. His public duties, he stated, occupied him only sixty half-hours in the year; but his studies suffered such interruptions from his domestic pupils and private lectures, that his most ardent wish was to be relieved from them, in order that he might have sufficient rest and leisure, before the close of his life, to finish and publish those great works which he had projected. In the event, therefore, of his returning to Pisa, he hoped that it would be the first object of his serene highness to give him leisure to complete his works without the drudgery of lecturing. He expresses his anxiety to gain his bread by his writings, and he promises to dedicate them to his serene master. He enumerates, among these books, two on the system of the universe, three on local motion, three books of mechanics, two on the demonstration of principles, and one of problems; besides treatises on sound and speech, on light and colours, on the tides, on the composition of continuous quant.i.ty, on the motions of animals, and on the military art. On the subject of his salary, he makes the following curious observations:--

"I say nothing," says he, "on the amount of my salary; being convinced that, as I am to live upon it, the graciousness of his highness would not deprive me of any of those comforts, of which, however, I feel the want of less than many others; and, therefore, I say nothing more on the subject. Finally, on the t.i.tle and profession of my service, I should wish that, to the t.i.tle of mathematician, his highness would add that of philosopher, as I profess to have studied a greater number of years in philosophy, than months in pure mathematics; and how I have profited by it, and if I can or ought to deserve this t.i.tle, I may let their highnesses see, as often as it shall please them to give me an opportunity of discussing such subjects in their presence with those who are most esteemed in this knowledge."

During the progress of this negotiation, Galileo went to Venice, on a visit to a friend, in the month of April or May 1609. Here he learned, from common rumour, that a Dutchman had presented to prince Maurice of Na.s.sau an optical instrument, which possessed the singular property of causing distant objects to appear nearer the observer. This Dutchman was Hans or John Lippershey, who, as has been clearly proved by the late Professor Moll of Utrecht,[8] was in the possession of a telescope made by himself so early as 2d October 1608. A few days afterwards, the truth of this report was confirmed by a letter which Galileo received from James Badorere at Paris, and he immediately applied himself to the consideration of the subject. On the first night after his return to Padua, he found, in the doctrines of refraction, the principle which he sought. He placed at the ends of a leaden tube two spectacle gla.s.ses, both of which were plain on one side, while one of them had its other side convex, and the other its second side concave, and having applied his eye to the concave gla.s.s, he saw objects pretty large and pretty near him. This little instrument, which magnified only three times, he carried in triumph to Venice, where it excited the most intense interest. Crowds of the princ.i.p.al citizens flocked to his house to see the magical toy; and after nearly a month had been spent in gratifying this epidemical curiosity, Galileo was led to understand from Leonardo Deodati, the Doge of Venice, that the senate would be highly gratified by obtaining possession of so extraordinary an instrument. Galileo instantly complied with the wishes of his patrons, who acknowledged the present by a mandate conferring upon him for life his professorship at Padua, and generously raising his salary from 520 to 1000 florins.[9]

[8] On the First Invention of Telescopes.--_Journ. R. Inst.i.t._, 1831., vol i., p. 496.