in the history of a glacier. Heaven-descended in its origin, it yet takes its mould from the hidden womb of the mountain which brought it forth. At first soft and ductile, it acquires a character and firmness of its own, as an inevitable destiny urges it on its onward career. Jostled and constrained by the crosses and inequalities of its prescribed path, hedged in by impassable barriers, which fix limits to its movements, it yields groaning to its fate, and still travels forward, scarred with the scars of many a conflict with opposing obstacles. All this while, although wasting, it is renewed by an unseen power-it evaporates, but is not consumed. On its surface it bears the spoils which, during the progress of existence, it has made its own;-often weighty burdens devoid of beauty or value-at times precious masses, sparkling with gems or with ice. Having at length attained its greatest width and extension, commanding admiration by its beauty and power, waste predominates over supply; the vital springs begin to fail; it stoops into an attitude of decrepitude; it drops the burdens one by one which it had borne so proudly aloft-its dissolution is inevitable. But as it is resolved into its elements, it takes all at once a new, and livelier, and disembarrassed form; from the wreck of its members it arises another, yet the same'

a noble, full-bodied, arrowy stream, which leaps rejoicing over the obstacles which before had stayed its progress, and hastens through fertile valleys towards a freer existence, and a final union in the ocean with the boundless and the infinite.'-(P. 387.)

It is not to supply what is unavoidably deficient, or to perfect what is necessarily incomplete, that, inappropriating the preceding lesson, we recall the important truth, that the material prototype of our moral progress is but the slave of the laws of gravity and temperature written on its bosom. Hence its inevitable destiny, its prescribed path, and its groaning submission to its fate. But the life which it typifies is guided by a gentler power and a lighter rein. Within the heart of man, and in letters woven with its fibres, there is written a law of which conscience is the interpreter, and there is implanted a will to appreciate or to reject its decisions. Hence may it take the broad or the narrow path, the light or the oppressive burden, and, having cast off in its youth or in its manhood the incubus of its moraines, it emerges from its icy cavern with a softer murmur, and in a purer stream.

But even when merged in the ocean, the glacier life has not rounded its cycle. Its waters re-distilled ascend in their aerial vehicle, tinting the mountain-tops, and clothing the sky in their ethereal blue; and, when liberated from their gaseous prison by the lightning's stroke, they again descend in showers of dewdrops, or in stars of crystal, throwing their rainbows and their' haloes round the luminaries of Heaven-the homage of the elements to Him who made them.

ART. VI. The Martyrs of Science; or, the Lives of Galileo, Tycho Brahé, and Kepler. By Sir DAVID BREWSter, K.H. D.C.L. 12mo. London: 1841.

I F the distinguished author of this unpretending little volume had undertaken to write the history of the origin of Physical Astronomy, he could not have thrown his narrative into a more convenient or interesting form, than by writing the lives of Galileo, Tycho Brahé, and Kepler. These three names occupy by far the most conspicuous place in the annals of Astronomy, between those of Copernicus and Newton. By explaining the phenomena of the celestial motions, on the hypothesis of the immobility of the sun and the twofold motion of the earth, Copernicus made the first step towards the true theory of the universe; but he did not discard the eccentrics and epicycles of the ancient faith; and the universally received dogma of antiquity-uniform motion in circular orbits-remained undisturbed. In order to proceed a step beyond the point at which Copernicus had arrived, observations of greater precision, and more distinct ideas respecting the laws of motion, were necessary. Tycho Brahé furnished the observations. Kepler, with infinite labour and sagacity, traced out their consequences, and proved from them that the planetary orbits are not circles but ellipses; and that the motions are not uniform, though regulated by a law remarkable for its simplicity and beauty. Galileo directed the telescope to the heavens; fortified the Copernican doctrine with new proofs; and, by the discovery of the laws of motion, prepared the way for the dynamical theories of Newton. In effecting this advance from formal to physical astronomy, no other individual contributed in any remarkable degree; hence the history of their labours includes that of the science itself, during one of the most interesting periods of its progress.

But if the three individuals just named are pre-eminently distinguished for their services to Astronomy, they are not less remarkable for their intellectual characters, and the incidents of their personal histories. They lived in an age of unusual intellectual activity, when Europe was rousing itself from the torpor of centuries, and gradually acquiring the characteristics of our own times. First in chronological order comes Tycho-the prototype of an age in a state of transition from ignorance and barbarism, to knowledge and refinement-devoting himself with equal zeal to the pursuits of astronomy and astrology, chemistry and alchemy, and in whose character religion and superstition, enlarged views

and abject credulity, were strangely blended. Next we have Kepler, also an astrologer, but while practising the art, railing at its vanity and worthlessness ;-indulging in the wildest reveries respecting the laws of the planetary motions, but rigidly subjecting all his fancies to the test of calculation; refuting his own hypotheses, when he found them inconsistent with observation, with as much patience and complacency as others employ in establishing the most important theories; speculating on the nature of attraction so as almost to anticipate Newton, yet stating at the same time his belief, that the solid globe of the earth is an enormous animal, and that the tides are produced by the spouting out of water through its gills! Lastly, we have the accomplished and courtly Galileo; a controversialist, a rhetorician, a man of the world; treating with sarcasm and ridicule the physical dogmas countenanced by the Church, yet living on terms of intimate friendship with its dignitaries; establishing the true system of the world with an overwhelming force of argument, and recanting his doctrines in submission to ecclesiastical authority. Characters thus marked would afford, under any circumstances, interesting subjects for biographical sketches; but in the present case, the interest is greatly increased by the accidents of life and position. The persecution of Galileo by the Catholic Church, for maintaining doctrines which are now regarded as the most certain truths of science; the injuries, real or imaginary, which compelled Tycho to abandon his Observatory, and exile himself from his country; the privations and miseries of Kepler, whose fate it was to be one day engaged in working out the laws of the universe, and the next in calculating nativities to procure bread for his children;-the incidents, in short, which entitle them to be regarded as martyrs of science-have procured for them the sympathies of the world, and given them a notoriety altogether independent of their scientific discoveries.

It is to the personal, rather than the scientific history of these three individuals, that Sir David Brewster has chiefly directed the attention of his readers in the present brief but interesting Memoirs; for though their services to science are distinctly set forth, and on the whole accurately appreciated, they are not dwelt upon at such length, or with so much detail, as to interfere with the popular character of the work. He does not profess to have had access to any new sources of information, or to have placed the already known facts in a new point of view; he has undertaken no laborious researches for the purpose of settling controverted points in history, or detecting minute errors or omissions in the accounts of previous biographers. In fact, the field had already been so diligently gleaned, as to leave but small hopes of

success in any attempt at novelty. The work derives its interest from the vivid portraitures it places before us of the characters of men whose labours occupy a large space in the history of science, and whose endeavours to enlighten the world were attended with so many personal sacrifices. It is written in an agreeable style; it abounds with traits of good feeling and generous sympathy; and, what may be regarded as of importance in a popular work, it represents science and its pursuits under an attractive and dignified aspect.

The life of Galileo, whom Sir David Brewster places at the head of his martyrs, has been given by his numerous biographers with great minuteness of detail. The materials for the scientific portion are of course collected from his various writings and literary correspondence; the anecdotes and personal traits rest chiefly on the authority of Viviani and Gherardini, the former of whom was one of his pupils, and revered his memory with a species of idolatry. Until recently, there was no good account of his life and discoveries in English; but the want was ably supplied by the elaborate, though somewhat discursive treatise, in the Library of Useful Knowledge, (1829 ;) a work which, it is but justice to say, has afforded our author considerable facilities in preparing the present Memoir. The recent historical work of Libri* has an account of Galileo which is very valuable from its fulness and research, and the care which has been taken to quote the original authorities for the various statements and anecdotes recorded; but unfortunately the author is a partizan, whose zeal to magnify his hero causes him to lose sight of all fairness and moderation in speaking of the characters and conduct of those to whom he was opposed.

Galileo Galilei, born at Pisa in 1564, was descended from a patrician, though decayed family, some of whose members had filled high civic offices in Florence. He was originally destined for commerce; but his studious disposition and promising talents led his father, Vincenzo Galilei, to entertain visions of success in a liberal profession; and, at the age of seventeen, he was sent to the university of Pisa to study medicine. His taste for geometry is said to have been developed by accidentally overhearing a lesson given by the Abbé Ricci to his pupils, the pages of the Grand Duke of Tuscany. Ricci happened to be a friend of Vincenzo Galilei; and, on becoming acquainted with the circumstance, and the progress already made by the young aspirant, admitted him to his course, and encouraged him to persevere.

* Histoire des Sciences Mathématiques en Italie. Tom. iv. 1841.

The study of Euclid was followed by that of Archimedés; and, after some ineffectual attempts on the part of his father to recall him to his professional studies, he was allowed to follow the bent of his genius. But Vincenzo, being burdened with a numerous family, was unable to maintain his son at Pisa; he applied for a bursary, and was disappointed; and Galileo was compelled to leave the university without taking his Doctor's degree.

Galileo's first essay in science was a treatise on the hydrostatical balance. This production fell into the hands of Guido Ubaldi, who forthwith conceived a friendship for the young author, and procured for him the appointment of lecturer on mathematics at Pisa, with a salary of sixty crowns. In this office he soon made himself conspicuous for the freedom and boldness of his attacks on the mechanical doctrines of Aristotle, whereby he excited the suspicions, and provoked the hatred of a strong party in the university. In 1592, he was appointed by the republic of Venice, again on the recommendation of Ubaldi, to the professorship of mathematics at Padua, with a salary of 180 florins. At that time, it was the custom (as it had been in the middle ages) to engage professors for a term of years. Galileo's appointment was for six years; but when the first period of his engagement had expired, he was re-elected for another period of six years, with an increased salary of 320 florins; and, in 1606, he was a third time appointed, and his salary raised to 520 florins. His popularity by this time had become so great, that his audience could not be accommodated. in the spacious lecture-rooms, and he was frequently obliged to adjourn to the open air.'

In 1609, Galileo, from some obscure hints, found out the construction of the telescope. The instrument excited intense curiosity at Venice; and he presented one to the Senate, • who ' acknowledged the present by a mandate, conferring on him for life his professorship at Padua, and generously raising his 'salary from 520 to 1000 florins.' In the following year he was induced, by offers from Cosmo, Grand Duke of Tuscany, to return to his native state; and he took up his residence at Florence, in the capacity of mathematician of the Grand Duke, with a salary of 1000 florins, and with no official duty excepting that which we may suppose would not press hard upon his leisure-of occasionally lecturing to foreign princes. This appointment Galileo continued to hold during the remainder of his life, enjoying the favour first of Cosmo, and afterwards of his successor, Ferdinand II., both of whom treated him with distinction; and used their influence with the court of Rome to shield him from the persecutions which were raised against him