The Essayist.

GALILEO.

A RETROSPECT of the past will show that in the midst of widespread ignorance and superstition, accompanied, as such generally is, with old and inveterate prejudices, a stray individual will be found, in whom genius sheds some bright rays through the surrounding gloom. We dwell on such with feelings of mingled pleasure and pain; gratified to observe truths made known for the first time to humanity, and openly asserted in the face of opposing bigotry, and false, though time-honoured preconceptions; while we heave a sigh, coupled with a sort of honest indignation, at the treatment those truths and truth-seeking individuals received from the hands of those by whom the very opposite ought to have been displayed. Among those who have distinguished themselves in this respect, Galileo is entitled to a prominent position.

Notwithstanding the progress made in Italy during the sixteenth century in literature and painting, so as to be termed, in that particular, "the golden age," as well as in the arts of sculp. ture and architecture, yet it appears that the various branches of science were most imperfectly understood, and the sublimities of astronomy obscured and distorted by the falsities of the Ptolemaic system. When erroneous dogmas are once established and long received as the truth, little inquiry as to their tenability is usually made, and ignorance and error, undisturbed, exercise their degrading influence. Galileo, however, was not one of those to be fettered by the opinions of the day, but boldly made inquiry, and rejected what did not stand the test of reason, and contradicted plain facts, although at the same time held up as infallible, and maintained at all costs against the least appearance of innovation. He early displayed that spirit of inquiry and independence of thought which afterwards so much characterized him. Being placed at the University of Pisa at the age of nineteen, the young student soon distinguished himself, not only by his capabilities, but also by his superior powers of application. The first work of Galileo, which was an essay on the "Hydrostatic Balance," excited attention, and secured for him the acquaintance of Guido Ubaldi, a learned Pisan, who recognized his rare gifts and showed a warm interest in his progress. Although designed for the medical profession, he showed so decided a bent for the pursuit of science, that the study of medicine was laid aside, with the reluctant consent of his father, who knew very well

that the latter would be a much surer road to respectability and worldly comfort.

The progress of Galileo in philosophic truth was maintained against a keen opposition by the abettors of the baseless and indefensible dogmas then taught by the schoolmen of the day. Ubaldi succeeded in introducing him to the Grand Duke Ferdinand I. de' Medici, who appointed him, in 1589, when only in his twenty-fifth year, to the mathematical chair at Pisa. This office, although most congenial to his tastes, yet he soon discovered that he had to assume the disagreeable position of supporting, in his turn, doctrines which he clearly saw could not bear a candid examination. This, however, he did not long submit to, and, as occasion offered, assailed these errors, not by mere assertions to the contrary, but by incontestable facts and self-evident demonstrations. One of the erroneous dogmas held at that time was, that bodies of unequal weights will fall to the ground with a velocity proportioned to their relative difference in that respect. Galileo, who is said to have been the first who formed a proper notion of the material nature of the atmosphere, at once saw the futile character of this established tenet, and justly accounted for the difference in the descent of various substances to the unequal resistance of the air. In order publicly to settle this disputed point, he went up to the top of the famous Campanile, or Leaning Tower of Pisa, from which he let fall a number of substances, differing considerably in weight, all of which came to the ground at so short intervals as at once to exhibit the incorrectness of the popular belief in this respect. Like other material substances, he supposed that, however comparatively little, the atmosphere must have weight and an incident occurred which very well illustrated, if not proved (at least, to his own satisfaction), the correctness of this idea. In the course of the erection of certain public works under the auspices of the then reigning Grand Duke of Tuscany, the water, it was perceived, could not be made to rise higher in the pumps than about thirty-two feet. The reason then alleged for water rising in a pump was, that nature abhors a vacuum; but when it was found that after all the rise of the water was limited, the dogma had to be mended; and instead of saying that "nature abhors a vacuum," it was necessary to say, "she abhors it only to the height of ten yards or so." Galileo, however, conjectured, and rightly, that the water rose from the pressure of the atmosphere; and as its weight was limited, it would only cause the liquid element to rise to a point at which it would be counterbalanced by it. Torricelli, a disciple of our philosopher, carried out the idea, which resulted in the invention by him of that useful scientific instrument, the barometer.

The views maintained by Galileo, and the able manner in which he defended them, so threatened the downfal of the

existing philosophy, that nothing less than his removal would satisfy his opponents. They did not oppose him by fair means— for they could not-but raised such a persecution and annoyance against him, that he thought it prudent to resign his office and set out for Florence. There he was well received by some of his friends, and met his former supporter, Guido Ubaldi, who also on this occasion rendered him valuable assistance. He was now appointed to occupy the mathematical chair of the university of Padua, and though he was engaged only for the space of six years, yet, at the expiry of which, was re-appointed for the same period with increased salary. Still continuing his inquiries while holding this situation, he invented the thermometer, and the proportional compass, or sector; and wrote some useful treatises on mechanics, astronomy, and other subjects. But perhaps the most important discovery, or rather invention, ever made by this remarkable man, was that of the telescope, which he succeeded in doing before quitting Padua, where he received that encouragement to which he was so much a stranger in after years. In narrating this discovery, we cannot do better than make the following quotation from one of his biographers" The year 1609 was signalized by a discovery on the part of Galileo which forms one of the most solid foundations of his glory. In the month of April a rumour was circulated in Venice that a Dutchman had presented to Count Maurice, of Nassau, an instrument, by which means distant objects appeared as if they were near at hand. On this slight and cursory hint, Galileo immediately applied himself to discover whether the thing was possible, conformably with the passage of the luminous rays through spherical glasses of various forms. Some attempts made with lenses, which he had at hand, produced the desired effect; and next day he gave an account of his success to his friends, which, in fact, was nothing less than the invention of the telescope. A short time afterwards, he presented several of these instruments to the senate of Venice, accompanied with a description, in which he unfolded the immense consequences for nautical and astronomical observations which would certainly result from the discovery; and in recompense of his ingenuity, his commission as professor was continued for life, with an allowance of salary triple that which he had previously received. Galileo neglected nothing calculated to evince his gratitude, or to add to the claims which had merited these favours. Indefatigable in his researches, he invented the microscope; he also improved the telescope, and soon brought it to a state fit to be applied to the observation of the heavens. He then perceived what as yet no mortal eye had ever seen,-the surface of the moon, like that of the earth, bristled with high mountains and ploughed with deep valleys; Venus, presenting, like the moon, phases which prove her rotundity; Jupiter, environed with four

satellites, who accompany him in his course; the milky way; the nebulæ; in a word, the whole heavens, bespangled with a countless multitude of stars, too small to be even perceived by the naked eye. It is more easy to conceive than describe the pleasure and delight which the first view of so many wonders must have inspired him withal, as well as the admiration which they could not fail to produce when they were known. A few days having sufficed to pass them in review, he hastened to announce his observations to the world, in a publication entitled Nuncius Sidereus; or, Celestial Courier,' which he dedicated to the princes of Medici, and which he continued at intervals in proportion as he discovered new objects. He also observed that Saturn sometimes appeared under the form of a simple disc, and sometimes with two appendages, which seemed two small planets; but it was reserved for another astronomer, Huygens, to demonstrate that these appearances were produced by the ring with which Saturn is surrounded. Galileo also discovered moveable spots on the globe or disc of the sun, whom the peripatetics had declared incorruptible, and did not hesitate from these to infer the rotation of that planet. He remarked that feeble light which, in the first and last quarters of the moon, renders visible, by means of the telescope, the part of her disc which is not then directly enlightened by the sun; and he concluded rightly that this effect was owing to the light reflected towards the moon by the earth. The continued observation of the spots of the moon satisfied him that that planet always presents nearly the same aspect; but in these he nevertheless recognized a species of periodic oscillation, to which he gave the name of libration, the exact laws of which were afterwards made known by Dominic Cassini. In a word, not less profound in following new truths to their consequences than subtile in discovering them, Galileo perceived the use to which the motions and eclipses of the satellites of Jupiter might be turned for the measure of longitudes; and he even undertook to make a sufficient number of observations of these stars to enable him to construct tables for the use of navigators."

Galileo being invited to Florence by the Grand Duke of Tuscany, who gave him the name of Mathematician Extraordinary, he left his comfortable situation at Padua. However willing the Grand Duke might be to afford liberal encouragement in the prosecution of his inquiries, yet, being subservient to the court of Rome, he soon found his mistake in quitting the Venetian states for the capital of Tuscany. Though he had friends in Florence, he had also enemies, who speedily assailed and reported him to the Inquisition, whose cruel bigotry and stupid ignorance, as displayed in the manner it dealt with him, are strong arguments against popish infallibility. The Ptolemaic system of philosophy, though half a century

before shaken by the discoveries of Copernicus, was still maintained; and, impressed with the infallible seal of the church of Rome, it was held as scriptural, and consequently, any one attempting to gainsay, was denounced a heretic. This theory, among other things, held that "all the celestial bodies were perfectly round, self-luminous, and not corrupted by any terres. trial tarnish;" that the sun, being the centre of the universe, did move round the earth from east to west. It is astonishing how far Copernicus went in his discoveries without the aid of the telescope. His only substitute for it was a rude triangle made of wood by his own hands, by means of which, however, he completed his great work on the revolutions of the heavenly bodies. Galileo, having a great advantage over Copernicus in the telescope, confirmed the discoveries of the latter. Indeed, the simplicity of the Copernican theory, when compared with the Ptolemaic, commends itself to every candid thinker, and the discriminating mind of Galileo did not fail to perceive, as he did not fail to avow, its correctness. Instead of holding that the celestial bodies were perfectly round and self-luminous, he affirmed that, like the earth, the moon was irregular in its surface, received its light from the sun, and was possibly inhabited; and instead of supporting the notion that they were uncorrupted by any terrestrial tarnish, he declared there were spots on the sun, which has since been amply confirmed. However correct and ably supported by sound arguments Galileo's views might be, it appears they made little impression in his favour on his enemies, who employed all available means to bring into discredit them as well as himself. Ridicule and falsehood were resorted to, and he finally was held up as a heretic who wished to deceive the people. In the defence which he made to the latter charge, a sentence occurs which shows how well he could assign a proper place for the book of nature without encroaching on that of revelation. It is the following:- In these and such other positions, which are not directly articles of faith, no man doubts but his holiness has always an absolute power of admitting or condemning them; but it is not in the power of any creature to make them to be true or false, otherwise than of their own nature and in fact they are." His arguments completely failed to avert the persecution hanging over him. The Inquisition ordered depositions to be drawn up against him. He appeared personally at Rome, and by his arguments temporarily silenced his persecutors, and afterwards obtained an interview with the pope, by whom he was required to abstain from teaching the heretical doctrines of the Copernican theory relative to the motion of the earth. Afterwards an assembly of Romish dignitaries issued a deliverance, denying as incorrect and heretical the doctrines held by Galileo, of the truth of which, by his own unwearied observations, he had not the least doubt.

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