CHAPTER IV.

In hoc quiescit vir nobilissimus, doctissimus et celeberrimus Dom. Johannes Keplerus, trium Imperatorum Rudolphi II., Mathiæ, et Ferdinandi II., per annos XXX,antea vero procerum Styriæ ab anno 1594 usque 1600, postea quoque astriacorum ordinum ab anno 1612 usque ad annum 1628, Mathematicus toti orbi Christiani, per monumenta publica cognitus, ab omnibus doctis, inter Principes Astronomiæ numeratus, qui propria manu assignatum post se reliquit tale Epitaphium.Mensus eram cœlos, nunc terræ metior umbras:Mens cœlestis erat, corporis umbra jacet.In Christo pie obiit anno Salutis 1630, die 5 Novembris, ætatis suæ sexagesimo.

Mensus eram cœlos, nunc terræ metior umbras:Mens cœlestis erat, corporis umbra jacet.

In Christo pie obiit anno Salutis 1630, die 5 Novembris, ætatis suæ sexagesimo.

This monument was not long preserved. It was destroyed during the wars which desolated Germany; and no attempt was made till 1786 to mark with honour the spot which contained such venerable remains. This attempt, however, failed, and it was not till 1803 that this great duty was paid to the memory of Kepler, by the Prince Bishop of Constance, who erected a handsome monumental temple near the place of his interment, and in the Botanical Garden of the city. The temple is surmounted by a sphere, and in the centre is a bust of Kepler in Carrara marble.

Kepler left behind him a wife and seven children—two by his first wife, Susanna and Louis; and three sons and two daughters by his second wife, viz.—Sebald, Cordelia, Friedman,Hildebert, and Anna Maria. The eldest of these, Susanna, was married a few months before her father’s death to Jacob Bartschius, his pupil, who was educated as a physician; and his son Louis died in 1663, while practising medicine at Konigsberg. The children by his second wife are said to have died young. They were left in very narrow circumstances; and though 24,000 florins were due to Kepler by the Emperor, yet only a part of this sum was received by Susanna, in consequence of her refusing to give up Tycho’s Observations till the debt was paid. Kepler composed a little work entitled “The Dream of John Kepler, or Lunar Astronomy,” the object of which was to describe the phenomena seen from the moon; but he died while he and Bartschius were engaged in its publication, and Bartschius having resumed the task, died also before its completion. Louis Kepler dreaded to meddle with a work which had proved so fatal to his father and his brother-in-law, but this superstitious feeling was overcome, and the work was published at Frankfort in 1636.

Number of Kepler’s published Works—His numerous Manuscripts in 22 folio volumes—Purchased by Hevelius, and afterwards by Hansch—Who publishes Kepler’s Life and Correspondence at the expense of Charles VI.—The History of the rest of his Manuscripts, which are deposited in the Library of the Academy of Sciences at St Petersburg—General Character of Kepler—His Candour in acknowledging his Errors—His Moral and Religious Character—His Astrological Writings and Opinions considered—His Character as an Astronomer and a Philosopher—The Splendour of his Discoveries—Account of his Methods of Investigating Truth.

Although the labours of Kepler were frequently interrupted by severe and long-continued indisposition, as well as by the pecuniary embarrassments in which he was constantly involved, yet the ardour and power of his mind enabled him to surmount all the difficulties of his position. Not only did he bring to a successfulcompletion the leading inquiries which he had begun, but he found leisure for composing an immense number of works more or less connected with the subject of his studies. Between 1594, when he published his Kalendar at Gratz, and 1630, the year of his death, he published no fewer thanthirty-threeseparate works; and he left behind himtwenty-twovolumes of manuscripts,sevenof which contain his epistolary correspondence.

The celebrated astronomer Hevelius, who was a cotemporary of Louis Kepler, purchased all these manuscripts from Kepler’s representatives. At the death of Hevelius they were bought by M. Gottlieb Hansch, a zealous mathematician, who was desirous of giving them to the world. For this purpose he issued a prospectus in 1714 for publishing them by subscription, in 22 volumes folio; but this plan having failed, he was introduced to Charles VI., who liberally obtained for him 1000 ducats to defray the expense of the publication, and an annual pension of 300 florins. With such encouragement, Hansch published in 1718, in one volume folio, the correspondence of Kepler, entitled “Epistolæ ad Joannem Keplerum, insertisad easdem responsionibus Keplerianis, quidquid hactenus reperiri potuerunt, opus novum, et cum Jo. Kepleri vita.”

The expenses of this volume unfortunately exhausted the 1000 ducats which had been granted by the Emperor, and, instead of being able to publish the rest of the MSS., Hansch was under the necessity of pledging them for 828 florins. Under these difficulties he addressed himself in vain to the celebrated Wolfius, to the Royal Society of London, and to other bodies that were likely to interest themselves in such a subject. In 1761, when M. De Murr of Nuremberg was in London, he made great exertions to obtain the MSS., and Dr Bradley is said to have been on the eve of purchasing them. The competition probably raised the demands of the proprietor, in whose hands they continued for many years. In 1773 they were offered for 4000 francs, and sometime afterwards M. De Murr purchased them for the Imperial Academy of Sciences at St Petersburg, in whose library they still remain. Euler, Lexell, and Kraft undertook the task of examining them, and selecting those that were best fitted for publication, but we believe thatno steps have yet been taken for executing this task, nor are we aware that science would derive any advantage from its completion.

Although, in drawing his own character, Kepler describes himself as “troublesome and choleric in politics and domestic matters,” yet the general events of his life indicate a more peaceful disposition than might have been expected from the peculiarities of his mind and the ardour of his temperament. On one occasion, indeed, he wrote a violent and reproachful letter to Tycho, who had given him no just ground of offence; but the state of Kepler’s health at that moment, and the necessitous circumstances in which he had been placed, present some palliation of his conduct. But, independent of this apology, his subsequent conduct was so truly noble as to reconcile even Tycho to his penitent friend. Kepler quickly saw the error which he committed; he lamented it with genuine contrition, and was anxious to remove any unfavourable impression which he might have given of his friend, by the most public confession of his error, and by the warmest acknowledgments of the kindness of Tycho.

In his relations with the scientific men of hisown times, Kepler conducted himself with that candour and love of truth which should always distinguish the philosopher. He was never actuated by any mean jealousy of his rivals. He never scrupled to acknowledge their high merits; and when the discoveries made by the telescope established beyond a doubt the errors of some of Kepler’s views, he willingly avowed his mistake, and never joined in the opposition which was made by many of his friends to the discoveries of Galileo. A striking example of this was exhibited in reference to his supposed discovery of Mercury on the sun’s disc. In the year 1607,[49]Kepler observed upon the face of the sun a dark spot, which he mistook for Mercury; but the day proving cloudy, he had not the means of determining by subsequent observations whether or not this opinion was well founded. As spots on the sun were at that time unknown, Kepler did not hesitate to publish the fact in 1607, in hisMercuriusin Sole visus; but when Galileo, a few years afterwards, discovered a great number of similar spots with the telescope, Kepler retracted his opinions, and acknowledged that Galileo’s discovery afforded an explanation, also, of many similar observations in old writers, which he had found it difficult to reconcile with the actual motions of Mercury.

Kepler was not one of those cold-hearted men who, though continually occupied in the study of the material world, and ambitious of the distinction which a successful examination of it confers, are yet insensible to the goodness and greatness of the Being who made and sustains it. His mind was cast in a better mould. The magnificence and harmony of the divine works excited in him not only admiration but love. He felt his own humility the farther he was allowed to penetrate into the mysteries of the universe; and sensible of the incompetency of his unaided powers for such transcendent researches, and recognising himself as but the instrument which the Almighty employed to make known his wonders, he never entered upon his inquiries without praying for assistance from above. This frame of mind was by no meansinconsistent with that high spirit of delight and triumph with which Kepler surveyed his discoveries. His was the unpretending ovation of success, not the ostentatious triumph of ambition; and if a noble pride did occasionally mingle itself with his feelings, it was the pride of being the chosen messenger of physical truth, not that of being the favoured possessor of superior genius. With such a frame of mind, Kepler was necessarily a Christian. The afflictions with which he was beset confirmed his faith and brightened his hopes: he bore them in all their variety and severity with Christian patience; and though he knew that this world was to be the theatre of his intellectual glory, yet he felt that his rest and his reward could be found only in another.

It is difficult to form any very intelligible idea of the nature and extent of Kepler’s astrological opinions, and of the degree of credit which he himself placed in the opinions that he did avow. In his Principles of Astrology, published in 1602, and in other works, he rails against the vanity and worthlessness of the ordinary astrology. He regards those who professed it as knaves and charlatans; and maintainsthat the planets and stars exercise no influence whatever over human affairs. He conceives, however, that certain harmonious configurations of suitable planets, like the spur to a horse, or a speech to an audience, have the power of exciting the minds of men to certain general actions or impulses; so that the only effect of these configurations is to operate along with the vital soul in producing results which would not otherwise have taken place. As an example of this, he states that those who are born when many aspects of the planets occur,generallyturn out busy and industrious, whether they be occupied in amassing wealth, managing public affairs, or prosecuting scientific studies. Kepler himself was born under a triple configuration, and hence, in his opinion, his ardour and activity in study; and he informs us that he knew a lady born under nearly the same configurations, “who not only makes no progress in literature, but troubles her whole family and occasions deplorable misery to herself.” This excitement of the faculties of sublunary natures, as he expresses it, by the colours and aspects and conjunctions of the planets, is regarded by Kepler as a fact, which he had deduced from observation,and which has “compelled his unwilling belief.” “I have been driven to this,” says he, “not by studying or admiring Plato, but singly and solely by observing seasons, and noting the aspects by which they are produced. I have seen the state of the atmosphere almost uniformly disturbed as often as the planets are in conjunction, or in the other configurations so celebrated among astrologers. I have noticed its tranquil state either when there are none or few such aspects, or when they are transitory and of short duration.” Had Kepler been able to examine these hasty and erroneous deductions by long continued observation, he would soon have found that the coincidence which he did observe was merely accidental, and he would have cheerfully acknowledged it. Speculations of this kind, however, are, from their very nature, less subject to a rigorous scrutiny; and a long series of observations is necessary either to establish or to overturn them. The industry of modern observers has now supplied this defect, and there is no point in science more certain than that the sun, moon, and planets do not exercise any influence on the general state of our atmosphere.

The philosophers in Kepler’s day, who had studied the phenomena of the tides, without having any idea of their cause, and who observed that they were clearly related to the daily motions of the two great luminaries, may be excused for the extravagance of their belief in supposing that the planets exercised other influences over “sublunary nature.” Although Kepler, in his Commentaries on Mars, had considered it probable that the waters of our ocean are attracted by the moon, as iron is by a loadstone, yet this opinion seems to have been a very transient one, as he long afterwards, in his System of Harmonies, stated his firm belief that the earth is an enormous living animal, and enumerates even the analogies between its habits and those of known animated beings. He considered the tides as waves produced by the spouting out of water through its gills, and he explains their relation to the solar and lunar motions by supposing that the terrene monster has, like other animals, its daily and nightly alternations of sleeping and waking.

From the consideration of Kepler’s astrological opinions, it is an agreeable transition to proceed to the examination of his high merits as anastronomer and a philosopher. As an experimental philosopher, or as an astronomical observer, Kepler does not lay claim to our admiration. He himself acknowledges, “that for observations his sight was dull, and for mechanical operations his hand was awkward.” He suffered much from weak eyes, and the delicacy of his constitution did not permit him to expose himself to the night air. Notwithstanding these hindrances, however, he added several observations to those of Tycho, which he made with two instruments that were presented to him by his friend Hoffman, the President of the States of Styria. These instruments were an iron sextant, 2½ feet in diameter, and a brass azimuthal quadrant 3½ feet in diameter, both of which were divided into single minutes of a degree. They were very seldom used, and we must regard the circumstances which disqualified Kepler for an observer, as highly favourable to the developement of those great powers which he directed with undivided energy to physical astronomy.

Even if Kepler had never turned his attention to the heavens, his optical labours would have given him a high rank among the original inquirersof his age; but when we consider him also as the discoverer of the three great laws which bear his name, we must assign him a rank next to that of Newton. The history of science does not present us with any discoveries more truly original, or which required for their establishment a more powerful and vigorous mind. The speculations of his predecessors afforded him no assistance. From the cumbrous machinery adopted by Copernicus, Kepler passed, at one step, to an elliptical orbit, with the sun in one of its foci, and from that moment astronomy became a demonstrative science. The splendid discoveries of Newton sprung immediately from those of Kepler, and completed the great chain of truths which constitute the laws of the planetary system. The eccentricity and boldness of Kepler’s powers form a striking contrast with the calm intellect and the enduring patience of Newton. The bright spark which the genius of the one elicited, was fostered by the sagacity of the other into a steady and a permanent flame.

Kepler has fortunately left behind him a full account of the methods by which he arrived at his great discoveries. What other philosophershave studiously concealed, Kepler has openly avowed, and minutely detailed; and we have no hesitation in considering these details as the most valuable present that has ever been given to science, and as deserving the careful study of all who seek to emulate his immortal achievements. It has been asserted that Newton made his discoveries by following a different method; but this is a mere assumption, as Newton has never favoured the world with any account of the erroneous speculations and the frequent failures which must have preceded his ultimate success. Had Kepler done the same, by recording only the final steps of his inquiries, his method of investigation would have obtained the highest celebrity, and would have been held up to future ages as a pattern for their imitation. But such was the candour of his mind, and such his inordinate love of truth, that he not only recorded his wildest fancies, but emblazoned even his greatest errors. If Newton had indulged us with the same insight into his physical inquiries, we should have witnessed the same processes which were employed by Kepler, modified only by the different characters and intensities of their imaginative powers.

When Kepler directed his mind to the discovery of a general principle, he set distinctly before him, and never once lost sight of, the explicit object of his search. His imagination, now unreined, indulged itself in the creation and invention of various hypotheses. The most plausible, or perhaps the most fascinating, of these was then submitted to a rigorous scrutiny; and the moment it was found to be incompatible with the results of observation and experiment, it was willingly abandoned, and another hypothesis submitted to the same severe ordeal. By thus gradually excluding erroneous views and assumptions, Kepler not only made a decided approximation to the object of his pursuit, but in the trials to which his opinions were submitted, and in the observations or experiments which they called forth, he discovered new facts and arrived at new views which directed his subsequent inquiries. By pursuing this method, he succeeded in his most difficult researches, and discovered those beautiful and profound laws which have been the admiration of succeeding ages. In tracing the route which he followed, it is easy for those who live under the light of modern science to say that hisfancies were often wild, and his labour often wasted; but, in judging of Kepler’s methods, we ought to place ourselves in his times, and invest ourselves with the opinions and the knowledge of his contemporaries.

In the infancy of a science there is no speculation so absurd as not to merit examination. The most remote and fanciful explanations of facts have often been found the true ones; and opinions which have in one century been objects of ridicule, have in the next been admitted among the elements of our knowledge. The physical world teems with wonders, and the various forms of matter exhibit to us properties and relations far more extraordinary than the wildest fancy could have conceived. Human reason stands appalled before this magnificent display of creative power, and they who have drunk deepest of its wisdom will be the least disposed to limit the excursions of physical speculation.

The influence of the imagination as an instrument of research, has, we think, been much overlooked by those who have ventured to give laws to philosophy. This faculty is of the greatest value in physical inquiries. If we useit as a guide, and confide in its indications, it will infallibly deceive us; but if we employ it as an auxiliary, it will afford us the most invaluable aid. Its operation is like that of the light troops which are sent out to ascertain the strength and position of an enemy. When the struggle commences, their services terminate; and it is by the solid phalanx of the judgment that the battle must be fought and won.

G. S. TULLIS, PRINTER, CUPAN.

FOOTNOTES[1]Childe Harold, canto iv. stanza liv.[2]Life of Galileo, Library of Useful Knowledge, p. 1.[3]De Insidentibus in Fluido.[4]Opere di Galileo. Milano, 1810, vol. iv. p. 248-257.[5]Life of Galileo, in Library of Useful Knowledge, p. 9.[6]Systema Cosmicum, Dial. ii. p. 121.[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.[8]On the First Invention of Telescopes.—Journ. R. Instit., 1831., vol i., p. 496.[9]VivianiVita del’ Galileo, p. 69.[10]De Telescopio.[11]Incredibili animi jucunditate.[12]Nescio quo fato ductus.[13]Berlin Ephemeris, 1788.[14]Edin. Phil. Journ. vol. vi. p. 313.[15]Life and Correspondence of Dr Bradley, Oxford, 1832, p. 533, See also his Supplement. Oxford, 1833, p. 17.[16]Professor Rigaud is of opinion that Galileo had discovered the solar spots at an earlier period than eighteen months before May 1612.[17]See page 40.[18]These interesting MSS. I have had the good fortune of seeing in the possession of my much valued friend, the late Professor Rigaud of Oxford.[19]Edin. Phil. Journ. 1822, vol. vi. p. 317. See Rigaud’s Life of Bradley, Supplement, p. 31.[20]Id. It., p. 37, 38.[21]Joh. Fabricii Phrysii de Maculis in Sole observatis, et apparente earum cum Sole conversione, Narratio. Wittemb. 1611.[22]It does not appear from the history of solar observations at what time, and by whom, coloured glasses were first introduced for permitting the eye to look at the sun with impunity. Fabricius was obviously quite ignorant of the use of coloured glasses. He observed the sun when he was in the horizon, and when his brilliancy was impaired by the interposition of thin clouds and floating vapours; and he advises those who may repeat his observations to admit at first to the eye a small portion of the sun’s light, till it is gradually accustomed to its full splendour. When the sun’s altitude became considerable, Fabricius gave up his observations, which he often continued so long that he was scarcely able, for two days together, to see objects with their usual distinctness. Fabricius speaks of observing the sun by admitting his rays through a smallholeinto a dark room, and receiving his image on paper; but he says nothing about a lens or a telescope being applied to the hole; and he does not say that he saw the spots of the sun in this way. Harriot also viewed the solar spots when the sun was near the horizon, or was visible through “thick layer and thin cloudes,” or through thin mist. On December 21, 1611, at a quarter past 2P.M., he observed the spots when the sky was perfectly clear, but his “sight was after dim for an houre.”Scheiner, in his “Appelles post Tabulam,” describes four different ways of viewing the spots; one of which is by theinterposition of blue or green glasses. His first method was to observe the sun near the horizon; the second was to view him through a transparent cloud; the third was to look at him through his telescope with a blue or a green glass of a proper thickness, and plane on both sides, or to use a thin blue glass when the sun was covered with a thin vapour or cloud; and the fourth method was to begin and observe the sun at his margin, till the eye gradually reached the middle of his disc.[23]The original of this letter is in the British Museum.[24]See Istoria e Dimonstrazioni, intorno alle macchie solare.Roma, 1616. See Opere di Galileo, vol, v., p. 131-293.[25]Discorso intorno alle cose che stanno in su l’acqua, o che in quella si muovono. Opere di Galileo, vol. ii. pp. 165-311.[26]Opere di Galileo, vol. ii. pp. 355-367.[27]Ibid. 367-390.[28]These three treatises occupy the whole of the third volume of the Opere di Galileo.[29]It is said that Galileo was cited to appear at Rome on this occasion; and the opinion is not without foundation.[30]Discorso delle Comete. Printed in the Opere di Galileo, vol. vi., pp. 117-191.[31]Printed in the Opere di Galileo, vol. vi., pp. 191-571.[32]A fine painting in gold, and a silver medal, and “a good quantity of agnus dei.”[33]Library of Useful Knowledge, Life of Galileo, chap. viii.[34]The communication between Florence and Rome was at this time interrupted by a contagious disease which had broken out in Tuscany.[35]It has been said, but upon what authority we cannot state, that when Galileo rose from his knees, he stamped on the ground, and said in a whisper to one of his friends, “E pur si muove.” “It does move, though.”—Life of Galileo, Lib. Useful Knowledge, part ii. p. 63.[36]It is a curious fact that Morin had about this time proposed to determine the longitude by the moon’s distance from a fixed star, and that the commissioners assembled in Paris to examine it requested Galileo’s opinion of its value and practicability. Galileo’s opinion was highly unfavourable. He saw clearly, and explained distinctly, the objection to Morin’s method, arising from the imperfection of the lunar tables, and the inadequacy of astronomical instruments; but he seemed not to be conscious that the very same objections applied with even greater force to his own method, which has since been supplanted by that of the French savant. See Life of Galileo, Library of Useful Knowledge, p. 94.[37]Regis Gallorum in Dania Legatus.[38]This office had been usually conferred on the King’s Chancellor.[39]Omne solum forti patria, et cœlum undique supra est.[40]The church of Tiers, where a monument has been erected to his memory.[41]See the Life of Kepler.[42]In his Preface to the Rudolphine Tables.[43]Cox’s Travels in Poland, &c., vol. v., p. 189, 190.[44]See the Life of Tycho, page 137.[45]Cassini was born in 1625, and died in 1712.[46]An interesting account of the steps by which Kepler proceeded will be found in Mr Drinkwater Bethune’s admirable Life of Kepler, in the Library of Useful Knowledge.[47]Life of Kepler, chap. vi.[48]These Ephemerides, from 1617 to 1620, were published at Linz in 1616. The one for 1620 was dedicated to Baron Napier of Merchiston.[49]It is said that Kepler saw this dark spotwhile looking at the sun in a camera obscura. As a camera obscura is actually a telescope, magnifying objects in proportion to the focal length of the lens employed, he may be said to have first seen these spots with the aid of an optical instrument.

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

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

[3]De Insidentibus in Fluido.

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

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

[6]Systema Cosmicum, Dial. ii. p. 121.

[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.

[8]On the First Invention of Telescopes.—Journ. R. Instit., 1831., vol i., p. 496.

[9]VivianiVita del’ Galileo, p. 69.

[10]De Telescopio.

[11]Incredibili animi jucunditate.

[12]Nescio quo fato ductus.

[13]Berlin Ephemeris, 1788.

[14]Edin. Phil. Journ. vol. vi. p. 313.

[15]Life and Correspondence of Dr Bradley, Oxford, 1832, p. 533, See also his Supplement. Oxford, 1833, p. 17.

[16]Professor Rigaud is of opinion that Galileo had discovered the solar spots at an earlier period than eighteen months before May 1612.

[17]See page 40.

[18]These interesting MSS. I have had the good fortune of seeing in the possession of my much valued friend, the late Professor Rigaud of Oxford.

[19]Edin. Phil. Journ. 1822, vol. vi. p. 317. See Rigaud’s Life of Bradley, Supplement, p. 31.

[20]Id. It., p. 37, 38.

[21]Joh. Fabricii Phrysii de Maculis in Sole observatis, et apparente earum cum Sole conversione, Narratio. Wittemb. 1611.

[22]It does not appear from the history of solar observations at what time, and by whom, coloured glasses were first introduced for permitting the eye to look at the sun with impunity. Fabricius was obviously quite ignorant of the use of coloured glasses. He observed the sun when he was in the horizon, and when his brilliancy was impaired by the interposition of thin clouds and floating vapours; and he advises those who may repeat his observations to admit at first to the eye a small portion of the sun’s light, till it is gradually accustomed to its full splendour. When the sun’s altitude became considerable, Fabricius gave up his observations, which he often continued so long that he was scarcely able, for two days together, to see objects with their usual distinctness. Fabricius speaks of observing the sun by admitting his rays through a smallholeinto a dark room, and receiving his image on paper; but he says nothing about a lens or a telescope being applied to the hole; and he does not say that he saw the spots of the sun in this way. Harriot also viewed the solar spots when the sun was near the horizon, or was visible through “thick layer and thin cloudes,” or through thin mist. On December 21, 1611, at a quarter past 2P.M., he observed the spots when the sky was perfectly clear, but his “sight was after dim for an houre.”Scheiner, in his “Appelles post Tabulam,” describes four different ways of viewing the spots; one of which is by theinterposition of blue or green glasses. His first method was to observe the sun near the horizon; the second was to view him through a transparent cloud; the third was to look at him through his telescope with a blue or a green glass of a proper thickness, and plane on both sides, or to use a thin blue glass when the sun was covered with a thin vapour or cloud; and the fourth method was to begin and observe the sun at his margin, till the eye gradually reached the middle of his disc.

Scheiner, in his “Appelles post Tabulam,” describes four different ways of viewing the spots; one of which is by theinterposition of blue or green glasses. His first method was to observe the sun near the horizon; the second was to view him through a transparent cloud; the third was to look at him through his telescope with a blue or a green glass of a proper thickness, and plane on both sides, or to use a thin blue glass when the sun was covered with a thin vapour or cloud; and the fourth method was to begin and observe the sun at his margin, till the eye gradually reached the middle of his disc.

[23]The original of this letter is in the British Museum.

[24]See Istoria e Dimonstrazioni, intorno alle macchie solare.Roma, 1616. See Opere di Galileo, vol, v., p. 131-293.

[25]Discorso intorno alle cose che stanno in su l’acqua, o che in quella si muovono. Opere di Galileo, vol. ii. pp. 165-311.

[26]Opere di Galileo, vol. ii. pp. 355-367.

[27]Ibid. 367-390.

[28]These three treatises occupy the whole of the third volume of the Opere di Galileo.

[29]It is said that Galileo was cited to appear at Rome on this occasion; and the opinion is not without foundation.

[30]Discorso delle Comete. Printed in the Opere di Galileo, vol. vi., pp. 117-191.

[31]Printed in the Opere di Galileo, vol. vi., pp. 191-571.

[32]A fine painting in gold, and a silver medal, and “a good quantity of agnus dei.”

[33]Library of Useful Knowledge, Life of Galileo, chap. viii.

[34]The communication between Florence and Rome was at this time interrupted by a contagious disease which had broken out in Tuscany.

[35]It has been said, but upon what authority we cannot state, that when Galileo rose from his knees, he stamped on the ground, and said in a whisper to one of his friends, “E pur si muove.” “It does move, though.”—Life of Galileo, Lib. Useful Knowledge, part ii. p. 63.

[36]It is a curious fact that Morin had about this time proposed to determine the longitude by the moon’s distance from a fixed star, and that the commissioners assembled in Paris to examine it requested Galileo’s opinion of its value and practicability. Galileo’s opinion was highly unfavourable. He saw clearly, and explained distinctly, the objection to Morin’s method, arising from the imperfection of the lunar tables, and the inadequacy of astronomical instruments; but he seemed not to be conscious that the very same objections applied with even greater force to his own method, which has since been supplanted by that of the French savant. See Life of Galileo, Library of Useful Knowledge, p. 94.

[37]Regis Gallorum in Dania Legatus.

[38]This office had been usually conferred on the King’s Chancellor.

[39]Omne solum forti patria, et cœlum undique supra est.

[40]The church of Tiers, where a monument has been erected to his memory.

[41]See the Life of Kepler.

[42]In his Preface to the Rudolphine Tables.

[43]Cox’s Travels in Poland, &c., vol. v., p. 189, 190.

[44]See the Life of Tycho, page 137.

[45]Cassini was born in 1625, and died in 1712.

[46]An interesting account of the steps by which Kepler proceeded will be found in Mr Drinkwater Bethune’s admirable Life of Kepler, in the Library of Useful Knowledge.

[47]Life of Kepler, chap. vi.

[48]These Ephemerides, from 1617 to 1620, were published at Linz in 1616. The one for 1620 was dedicated to Baron Napier of Merchiston.

[49]It is said that Kepler saw this dark spotwhile looking at the sun in a camera obscura. As a camera obscura is actually a telescope, magnifying objects in proportion to the focal length of the lens employed, he may be said to have first seen these spots with the aid of an optical instrument.

Transcriber’s Notes and ErrataThe following typographical errors were corrected:PageErrorCoorection50betwenbetween71his hishis100secretrysecretary143there sidencethe residence234guaginggauging

The following typographical errors were corrected:

PageErrorCoorection50betwenbetween71his hishis100secretrysecretary143there sidencethe residence234guaginggauging

Back to Index Next