'In the second place, the distance between the centres of Venus and the Sun I found by three observations to be as follows:—

The Hour. Distance of the Centres. At 3.15 by the clock 14' 24'' " 3.35 " 13' 30'' " 3.45 " 13' 0'' " 3.50 the apparent sunset.

The true setting being 3.45, and the apparent about 5 minutes later, the difference being caused by refraction. The clock therefore was sufficiently correct.

'In the third place I found after careful and repeated observation that the diameter of Venus, as her shadow was depicted on the paper, was larger indeed than the thirtieth part of the solar diameter, though not more so than the sixth, or at the utmost the fifth of such a part. Therefore let the diameter of the Sun be to the diameter of Venus as 30' to 1' 12''. Certainly her diameter never equalled 1' 30'', scarcely perhaps 1' 20'', and this was evident as well when the planet was near the Sun's limb as when far distant from it.



'This observation was made in an obscure village where I have long been in the habit of observing, about fifteen miles to the north of Liverpool, the latitude of which I believe to be 53 deg. 20', although by common maps it is stated at 54 deg. 12', therefore the latitude of the village will be 53 deg. 35', and longitude of both 22 deg. 30' from the Fortunate Islands, now called the Canaries. This is 14 deg. 15' to the west of Uraniburg in Denmark, the longitude of which is stated by Brahe, a native of the place, to be 36 deg. 45' from these islands.

'This is all I could observe respecting this celebrated conjunction during the short time the Sun remained in the horizon: for although Venus continued on his disc for several hours, she was not visible to me longer than half an hour on account of his so quickly setting. Nevertheless, all the observations which could possibly be made in so short a time I was enabled by Divine Providence to complete so effectually that I could scarcely have wished for a more extended period. The inclination was the only point upon which I failed to attain the utmost precision; for, owing to the rapid motion of the Sun it was difficult to observe with certainty to a single degree, and I frankly confess that I neither did nor could ascertain it. But all the rest is sufficiently accurate, and as exact as I could desire.'

Besides having ascertained that the diameter of Venus subtends an angle not much greater than one minute of arc, Horrox reduced the horizontal solar parallax from fifty-seven seconds as stated by Kepler to fourteen seconds, a calculation within one and a half second of the value assigned to it by Halley sixty years after. He also reduced the Sun's semi-diameter.

Crabtree, to whom Horrox refers as 'his most esteemed friend and a person who has few superiors in mathematical learning,' made preparations to observe the transit similar to those already described. But the day was unfavourable, dark clouds obscured the sky and rendered the Sun invisible. Crabtree was in despair, and relinquished all hope of being able to witness the conjunction. However, just before sunset there was a break in the clouds, and the Sun shone brilliantly for a short interval. Crabtree at once seized his opportunity, and to his intense delight observed the planet fully entered upon the Sun's disc. Instead of proceeding to take observations, he was so overcome with emotion at the sight of the phenomenon, that he continued to gaze upon it with rapt attention, nor did he recover his self-possession until the clouds again hid from his view the setting Sun.[4]

Crabtree's observation of the transit was, however, not a fruitless one. He drew from memory a diagram showing the exact position of Venus on the Sun's disc, which corresponded in every respect with Horrox's observation; he also estimated the diameter of the planet to be 7/200 that of the Sun, which when calculated gives one minute three seconds; Horrox having found it to be one minute twelve seconds. This transit of Venus is remarkable as having been the first ever observed of which there is any record, and for this we are indebted to the genius of Horrox, who by a series of calculations, displaying a wonderfully accurate knowledge of mathematics, was enabled to predict the occurrence of the phenomenon on the very day, and almost at the hour it appeared, and of which he and his friend Crabtree were the only observers.

Having thought it desirable to write an account of the transit, Horrox prepared an elegant Latin treatise, entitled 'Venus in Sole Visa'—'Venus seen in the Sun;' but not knowing what steps to take with regard to its publication, he requested Crabtree to communicate with his bookseller and obtain his advice on the matter.

In the meantime Horrox returned to Toxteth, and arranged to fulfil a long-promised visit to Crabtree, which he looked forward to with much pleasure, as it would afford him an opportunity of discussing with his friend many matters of interest to both. This visit was frustrated in a manner altogether unexpected. For we read that Horrox was seized with a sudden and severe illness, the nature of which is not known, and that his death occurred on the day previous to that of his intended visit to his friend at Broughton. He expired on January 3, 1641, when in the 23rd year of his age.

His death was a great grief to Crabtree, who, in one of his letters, describes it as 'an irreparable loss:' and it is believed that he only survived him a few years.[5] Of the papers left by Horrox, only a few have been preserved, and these were discovered in Crabtree's house after his death. Among them was his treatise on the transit of Venus which, with other papers, was purchased by Dr. Worthington, Fellow of Emmanuel College, Cambridge, a man of learning, who was capable of appreciating their value. Ultimately, the treatise fell into the possession of Hevelius, a celebrated German astronomer, who published it along with a dissertation of his own, describing a transit of Mercury.

Horrox did not live to see any of his writings published, nor was any monument erected to his memory until nearly two hundred years after his death. But his name, though long forgotten except by astronomers, is now engraved on marble in Westminster Abbey. Had his life been spared, it would have been difficult to foretell to what eminence and fame he might have risen, or what further discoveries his genius might have enabled him to make. Few among English astronomers will hesitate to rank him next with the illustrious Newton, and all will agree with Herschel, who called him 'the pride and the boast of British Astronomy.'

WILLIAM GASCOIGNE was born in 1612, in the parish of Rothwell, in the county of York, and afterwards resided at Middleton, near Leeds.

He was a man of an inventive turn of mind, and possessed good abilities, which he devoted to improving the methods of telescopic observation.

At an early age he was occupied in observing celestial objects, making researches in optics, and acquiring a proficient knowledge of astronomy.

Among his acquaintances were Crabtree and Horrox, with whom he carried on a correspondence on matters appertaining to their favourite study.

The measurement of small angles was found at all times to be one of the greatest difficulties which astronomers had to contend with. Tycho Brahe was so misled by his measurements of the apparent diameters of the Sun and Moon, that he concluded a total eclipse of the Sun was impossible.

Gascoigne overcame this difficulty by his invention of the micrometer. This instrument, when applied to a telescope, was found to be of great service in the correct measurement of minute angles and distances, and was the means of greatly advancing the progress of practical astronomy in the seventeenth century. A micrometer consists of a short tube, across the opening of which are stretched two parallel wires; these being intersected at right angles by a third. The wires are moved to or from each other by delicately constructed screws, to which they are attached. Each revolution, or part of a revolution, of a screw indicates the distance by which the wires are moved.

This apparatus, when placed in the focus of a lens, gives very accurate measurements of the diameters of celestial objects. It was successfully used by Gascoigne in determining the apparent diameters of the Sun, Moon, and several of the planets, and the mutual distances of the stars which form the Pleiades.

Crabtree, after having paid Gascoigne a visit in 1639, describes in a letter to Horrox the impression created on his mind by the micrometer. He writes: 'The first thing Mr. Gascoigne showed me was a large telescope, amplified and adorned with new inventions of his own, whereby he can take the diameters of the Sun or Moon, or any small angle in the heavens or upon the earth, most exactly through the glass to a second.'

The micrometer is now regarded as an indispensable appliance in the observatory; the use of a spider web reticule instead of wire having improved its efficiency. Gascoigne was one of the earliest astronomers who recognised the value of the Keplerian telescope for observational purposes, and Sherburn affirms that he was the first to construct an instrument of this description having two convex lenses. Whether this be true or not, it is certain that he applied the micrometer to the telescope, and was the first to use telescopic sights, by means of which he was able to fix the optical axis of his telescope, and ascertain by observation the apparent positions of the heavenly bodies.

Crabtree, in a letter to Gascoigne, says: 'Could I purchase it with travel, or procure it with gold, I would not be without a telescope for observing small angles in the heavens; or want the use of your device of a glass in a cane upon the movable ruler of your sextant, as I remember for helping to the exact point of the Sun's rays.'

It was not known until the beginning of the eighteenth century that Gascoigne had invented and used telescopic sights for the purpose of making accurate astronomical observations. The accidental discovery of some documents which contained a description of his appliances was the means by which this became known.

Townley states that Gascoigne had completed a treatise on optics, which was ready for publication, but that no trace of the manuscript could be discovered after his death. Having embraced the Royalist cause, William Gascoigne joined the forces of Charles I., and fell in the battle of Marston Moor on July 2, 1644.

The early death of this young and remarkably clever man was a severe blow to the science of astronomy in England.

The invention of logarithms, by Baron Napier, of Merchistoun, was found to be of inestimable value to astronomers in facilitating and abbreviating the methods of astronomical calculation.

By the use of logarithms, arithmetical computations which necessitated laborious application for several months could with ease be completed in as many days. It was remarked by Laplace that this invention was the means of doubling the life of an astronomer, besides enabling him to avoid errors and the tediousness associated with long and abstruse calculations.

THOMAS HARRIOT, an eminent mathematician, and an assiduous astronomer, made some valuable observations of the comet of 1607. He was one of the earliest observers who made use of the telescope, and it was claimed on his behalf that he discovered Jupiter's satellites, and the spots on the Sun, independently of Galileo. Other astronomers have been desirous of sharing this honour, but it has been conclusively proved that Galileo was the first who made those discoveries.

The investigations of Norwood and Gilbert, the mechanical genius of Hooke, and the patient researches of Flamsteed—the first Astronomer Royal—were of much value in perfecting many details associated with the study of astronomy.

The Royal Observatory at Greenwich was founded in 1675. The building was erected under a warrant from Charles II. It announces the desire of the Sovereign to build a small observatory in the park at Greenwich, 'in order to the finding out of the longitude for perfecting the art of navigation and astronomy.' This action on the part of the King may be regarded as the first public acknowledgment of the usefulness of astronomy for national purposes.

Since its erection, the observatory has been presided over by a succession of talented men, who have raised it to a position of eminence and usefulness unsurpassed by any similar institution in this or any other country. The well-known names of Flamsteed, Halley, Bradley, and Airy, testify to the valuable services rendered by those past directors of the Greenwich Observatory in the cause of astronomical science.

If we take a general survey of the science of astronomy as it existed from 1608 to 1674—a period that embraced the time in which Milton lived—we shall find that it was still compassed by ignorance, superstition, and mystery. Astrology was zealously cultivated; most persons of rank and position had their nativity or horoscope cast, and the belief in the ruling of the planets, and their influence on human and terrestrial affairs, was through long usage firmly established in the public mind. Indeed, at this time, astronomy was regarded as a handmaid to astrology; for, with the aid of astronomical calculation, the professors of this occult science were enabled to predict the positions of the planets, and by this means practised their art with an apparent degree of truthfulness.

Although over one hundred years had elapsed since the death of Copernicus, his theory of the solar system did not find many supporters, and the old forms of astronomical belief still retained their hold on the minds of the majority of philosophic thinkers. This can be partly accounted for, as many of the Ptolemaic doctrines were at first associated with the Copernican theory, nor was it until a later period that they were eliminated from the system.

Though Copernicus deserved the credit of having transferred the centre of our system from the Earth to the Sun, yet his theory was imperfect in its details, and contained many inaccuracies. He believed that the planets could only move round the Sun in circular paths, nor was he capable of conceiving of any other form of orbit in which they could perform their revolutions. He was therefore compelled to retain the use of cycles and epicycles, in order to account for irregularities in the uniformly circular motions of those bodies.

We are indebted to the genius of Kepler for having placed the Copernican system upon a sure and irremovable basis, and for having raised astronomy to the position of a true physical science. By his discovery that the planets travel round the Sun in elliptical orbits, he was enabled to abolish cycles and epicycles, which created such confusion and entanglement in the system, and to explain many apparent irregularities of motion by ascribing to the Sun his true position with regard to the motions of the planets.

After the death of Kepler, which occurred in 1630, the most eminent supporter of the Copernican theory was the illustrious Galileo, whose belief in its accuracy and truthfulness was confirmed by his own discoveries.

Five of the planets were known at this time—viz. Mercury, Venus, Mars, Jupiter, and Saturn; the latter, which revolves in its orbit at a profound distance from the Sun, formed what at that time was believed to be the boundary of the planetary system. The distance of the Earth from the Sun was approximately known, and the orb was observed to rotate on his axis.

It was also ascertained that the Moon shone by reflected light, and that her surface was varied by inequalities resembling those of our Earth. The elliptical form of her orbit had been discovered by Horrox, and her elements were computed with a certain degree of accuracy.

The cloudy luminosity of the Milky Way had been resolved into a multitude of separate stars, disclosing the immensity of the stellar universe.

The crescent form of the planet Venus, the satellites of Jupiter and of Saturn, and the progressive motion and measurement of light, had also been discovered. Observations were made of transits of Mercury and Venus, and refracting and reflecting telescopes were invented.

The law of universal gravitation, a power which retains the Earth and planets in their orbits, causing them year after year to describe with unerring regularity their oval paths round the Sun, was not known at this time. Though Newton was born in 1642, he did not disclose the results of his philosophic investigations until 1687—thirteen years after the death of Milton—when, in the 'Principia,' he announced his discovery of the great law of universal gravitation.

Kepler, though he discovered the laws of planetary motion, was unable to determine the motive force which guided and retained those bodies in their orbits. It was reserved for the genius of Newton to solve this wonderful problem. This great philosopher was able to prove 'that every particle of matter in the universe attracts every other particle with a force proportioned to the mass of the attracting body, and inversely as the square of the distance between them.' Newton was capable of demonstrating that the force which guides and retains the Earth and planets in their orbits resides in the Sun, and by the application of this law of gravitation he was able to explain the motions of all celestial bodies entering into the structure of the solar system.

This discovery may be regarded as the crowning point of the science of astronomy, for, upon the unfailing energy of this mysterious power depend the order and stability of the universe, extending as it does to all material bodies existing in space, guiding, controlling, and retaining them in their several paths and orbits, whether it be a tiny meteor, a circling planet, or a mighty sun.

The nature of cometary bodies and the laws which govern their motions were at this time still enshrouded in mystery, and when one of those erratic wanderers made its appearance in the sky it was beheld by the majority of mankind with feelings of awe and superstitious dread, and regarded as a harbinger of evil and disaster, the precursor of war, of famine, or the overthrow of an empire.

Newton, however, was able to divest those bodies of the mystery with which they were surrounded by proving that any conic section may be described about the Sun, consistent with the law of gravitation, and that comets, notwithstanding the eccentricity of their orbits, obey the laws of planetary motion.

Beyond the confines of our solar system, little was known of the magnitude and extent of the sidereal universe which occupies the infinitude of space by which we are surrounded. The stars were recognised as self-luminous bodies, inconceivably remote, and although they excited the curiosity of observers, and conjectures were made as to their origin, yet no conclusive opinions were arrived at with regard to their nature and constitution, and except that they were regarded as glittering points of light which illumine the firmament, all else appertaining to them remained an unravelled mystery. Even Copernicus had no notion of a universe of stars.

Galileo, by his discovery that the galaxy consists of a multitude of separate stars too remote to be defined by ordinary vision, demonstrated how vast are the dimensions of the starry heavens, and on what a stupendous scale the universe is constructed. But at this time it had not occurred to astronomers, nor was it known until many years after, that the stars are suns which shine with a splendour resembling that of our Sun, and in many instances surpassing it. It was not until this truth became known that the glories of the sidereal heavens were fully comprehended, and their magnificence revealed. It was then ascertained that the minute points of light which crowd the fields of our largest telescopes, in their aggregations forming systems, clusters, galaxies, and universes of stars, are shining orbs of light, among the countless multitudes of which our Sun may be numbered as one.



CHAPTER III

MILTON'S ASTRONOMICAL KNOWLEDGE

It would be reasonable to imagine that Milton's knowledge of astronomy was comprehensive and accurate, and superior to that possessed by most scientific men of his age. His scholarly attainments, his familiarity with ancient history and philosophy, his profound learning, and the universality of his general knowledge, would lead one to conclude that the science which treats of the mechanism of the heavens, and especially the observational part of it—which at all times has been a source of inspiration to poets of every degree of excellence—was to him a study of absorbing interest, and one calculated to make a deep impression upon his devoutly poetical mind. The serious character of Milton's verse, and the reverent manner in which celestial incidents and objects are described in it, impress one with the belief that his contemplation of the heavens, and of the orbs that roll and shine in the firmament overhead, afforded him much enjoyment and meditative delight. For no poet, in ancient or in modern times, has introduced into his writings with such frequency, or with such pleasing effect, so many passages descriptive of the beauty and grandeur of the heavens. No other poet, by the creative effort of his imagination, has soared to such a height; nor has he ever been excelled in his descriptions of the celestial orbs, and of the beautiful phenomena associated with their different motions.

In his minor poems, which were composed during his residence at Horton, a charming rural retreat in Buckinghamshire, where the freshness and varied beauty of the landscape and the attractive aspects of the midnight sky were ever before him, we find enchanting descriptions of celestial objects, and especially of those orbs which, by their brilliancy and lustre, have always commanded the admiration of mankind.

For example, in 'L'Allegro' there are the following lines:—

Right against the eastern gate Where the great Sun begins his state, Robed in flames and amber light, The clouds in thousand liveries dight;

and in 'Il Penseroso'—

To behold the wandering Moon, Riding near her highest noon, Like one that had been led astray Through the heaven's wide pathless way, And oft as if her head she bowed, Stooping through a fleecy cloud.

In the happy choice of his theme, and by the comprehensive manner in which he has treated it, Milton has been enabled by his poetic genius to give to the world in his 'Paradise Lost' a poem which, for sublimity of thought, loftiness of imagination, and beauty of expression in metrical verse, is unsurpassed in any language.

It is, however, our intention to deal only with those passages in the poem in which allusion is made to the heavenly bodies, and to incidents and occurrences associated with astronomical phenomena. In the exposition and illustration of these it has been considered desirable to adopt the following general classification:—

1. To ascertain the extent of Milton's astronomical knowledge.

2. To describe the starry heavens and the celestial objects mentioned in 'Paradise Lost.'

3. To exemplify the use which Milton has made of astronomy in the exercise of his imaginative and descriptive powers.

In the earlier half of the seventeenth century the Ptolemaic theory—by which it was believed that the Earth was the immovable centre of the universe, and that round it all the heavenly bodies completed a diurnal revolution—still retained its ascendency over the minds of men of learning and science, and all the doctrines associated with this ancient astronomical creed were still religiously upheld by the educated classes among the peoples inhabiting the different civilised regions of the globe. The Copernican theory—by which the Sun is assigned the central position in our system, with the Earth and planets revolving in orbits round him—obtained the support of a few persons of advanced views and high scientific attainments, but its doctrines had not yet seriously threatened the supremacy of the older system. Though upwards of one hundred years had elapsed since the death of Copernicus, yet the doctrines associated with the system of which he was the founder were but very tardily adopted up to this time. There were several reasons which accounted for this. The Copernican system was at first imperfect in its details, and included several of the Ptolemaic, doctrines which rendered it less intelligible, and retarded its acceptance by persons who would otherwise have been inclined to adopt it. Copernicus believed that the planets travelled round the Sun in circular paths. This necessitated the retention of cycles and epicycles, which gave rise to much confusion; nor was it until Kepler made his great discovery of the ellipticity of the planetary orbits that they were eliminated from the system.

As the Ptolemaic system of the universe held complete sway over the minds of men for upwards of twenty centuries, it was difficult to persuade many persons to renounce the astronomical beliefs to which they were so firmly attached, in favour of those of any other system; so that the overthrow of this venerable theory required a lengthened period of time for its accomplishment.

It was thus in his earlier years, when Milton devoted his time to the study of literature and philosophy, which he read extensively when pursuing his academic career at Christ's College, Cambridge, and afterwards at Horton, where he spent several years in acquiring a more proficient knowledge of the literary, scientific, and philosophical writings of the age, that he found the beliefs associated with the Ptolemaic theory adopted without doubt or hesitation by the numerous authors whose works he perused. His knowledge of Italian enabled him to become familiar with Dante—one of his favourite authors, whose poetical writings were deeply read by him, and who, in the elaboration of his poem, the 'Divina Commedia,' included the entire Ptolemaic cosmology.

In England the Copernican theory had few supporters, and the majority of those who represented the intellect and learning of the country still retained their adherence to the old form of astronomical belief. We therefore find that Milton followed the traditional way of thinking by adopting the views associated with the Ptolemaic theory.

According to the Ptolemaic system, the Earth was regarded as the immovable centre of the universe, and surrounding it were ten crystalline spheres, or heavens, arranged in concentric circles, the larger spheres enclosing the smaller ones; and within those was situated the cosmos, or mundane universe, usually described as 'the Heavens and the Earth.' To each of the first seven spheres there was attached a heavenly body, which was carried round the Earth by the revolution of the crystalline.

1st sphere: that of the Moon.

2nd sphere: that of the planet Mercury.

3rd sphere: that of the planet Venus.

4th sphere: that of the Sun; regarded as a planet.

5th sphere: that of the planet Mars.

6th sphere: that of the planet Jupiter.

7th sphere: that of the planet Saturn.

8th sphere: that of the fixed stars.



The eighth sphere included all the fixed stars, and was called the firmament, because it was believed to impart steadiness to the inner spheres, and, by its diurnal revolution, to carry them round the Earth, causing the change of day and night.

The separate motions of the spheres, revolving with different velocities, and at different angles to each other, accounted for the astronomical phenomena associated with the orbs attached to each. According to Ptolemy's scheme, the eighth sphere formed the outermost boundary of the universe; but later astronomers added to this system two other spheres—a ninth, called the Crystalline, which caused Precession of the Equinoxes; and a tenth, called the Primum Mobile, or First Moved, which brought about the alternation of day and night, by carrying all the other spheres round the Earth once in every twenty-four hours. The Primum Mobile enclosed, as if in a shell, all the other spheres, in which was included the created universe, and, although of vast dimensions, its conception did not overwhelm the mind in the same manner that the effort to comprehend infinitude does.

Beyond this last sphere there was believed to exist a boundless, uncircumscribed region, of immeasurable extent, called the Empyrean, or Heaven of Heavens, the incorruptible abode of the Deity, the place of eternal mysteries, which the comprehension of man was unable to fathom, and of which it was impossible for his mind to form any conception. Such were the imaginative beliefs upon which this ancient astronomical theory was founded, that for a period of upwards of two thousand years held undisputed sway over the minds of men, and exercised during that time a predominating influence upon the imagination, thoughts, and conceptions of all those who devoted themselves to literature, science, and art. Of the truthfulness of this assertion there is ample evidence in the poetical, philosophical, and historical writings of ancient authors, whose ideas and conceptions regarding the created universe were limited and circumscribed by this form of astronomical belief. In the works of more recent writers we find that it continued to assert its influence; and among our English poets, from Chaucer down to Shakespeare, there are numerous references to the natural phenomena associated with this system, and most frequently expressed by poetical allusions to 'the music of the spheres.'

The ideas associated with the Ptolemaic theory were gratifying to the pride and vanity of man, who could regard with complacency the paramount importance of the globe which he inhabited, and of which he was the absolute ruler, fixed in the centre of the universe, and surrounded by ten revolving spheres, that carried along with them in their circuit all other celestial bodies—Sun, Moon, and stars, which would appear to have been created for his delectation, and for the purpose of ministering to his requirements. But when the Copernican theory became better understood, and especially after the discovery of the law of universal gravitation, this venerable system of the universe, based upon a pile of unreasonable and false hypotheses, after an existence of over twenty centuries, sank into oblivion, and was no more heard of.

Milton's Ptolemaism is apparent in some of his shorter pieces, and also in his minor poems, 'Arcades' and 'Comus.' His 'Ode on the Nativity' is written in conformity with this belief, and the expression,

Ring out ye crystal spheres,

indicates a poetical allusion to this theory. But as Milton grew older his Ptolemaism became greatly modified, and there are good reasons for believing that in his latter years he renounced it entirely in favour of Copernicanism. When on his continental tour in 1638, he made the acquaintance of eminent men who held views different from those with which he was familiar; and in his interview with Galileo at Arcetri, the aged astronomer may have impressed upon his mind the superiority of the Copernican theory, in accounting for the occurrence of celestial phenomena, as compared with the Ptolemaic.

On his return to England from the Continent, Milton took up his residence in London, and lived in apartments in a house in St. Bride's Churchyard. Having no regular vocation, and not wishing to be dependent upon his father, he undertook the education of his two nephews, John and Edward Phillips, aged nine and ten years respectively. From St. Bride's Churchyard he removed to a larger house in Aldersgate, where he received as pupils the sons of some of his most intimate acquaintances. In the list of subjects which Milton selected for the purpose of imparting instruction to those youths he included astronomy and mathematics, which formed part of the curriculum of this educational establishment. The text-book from which he taught his nephews and other pupils astronomy was called 'De Sphaera Mundi,' a work written by Joannes Sacrobasco (John Holywood) in the thirteenth century. This book was an epitome of Ptolemy's 'Almagest,' and therefore entirely Ptolemaic in its teaching. It enjoyed great popularity during the Middle Ages, and is reported to have gone through as many as forty editions.

The selection of astronomy as one of the subjects in which Milton instructed his pupils affords us evidence that he must have devoted considerable time and attention to acquiring a knowledge of the facts and details associated with the study of the science. In the attainment of this he had to depend upon his own exertions and the assistance derived from astronomical books; for at this time astronomy received no recognition as a branch of study at any of the universities; and in Britain the science attracted less attention than on the Continent, where the genius of Kepler and Galileo elevated it to a position of national importance.

We shall find as we proceed that Milton's knowledge of astronomy was comprehensive and accurate; that he was familiar with the astronomical reasons by which many natural phenomena which occur around us can be explained; and that he understood many of the details of the science which are unknown to ordinary observers of the heavens.

It is remarkable how largely astronomy enters into the composition of 'Paradise Lost,' and we doubt if any author could have written such a poem without possessing a knowledge of the heavens and of the celestial orbs such as can only be attained by a proficient and intimate acquaintance with this science.

The arguments in favour of or against the Ptolemaic and Copernican theories were well known to Milton, even as regards their minute details; and in Book viii. he introduces a scientific discussion based upon the respective merits of those theories. The configuration of the celestial and terrestrial spheres, and the great circles by which they are circumscribed, he also knew. The causes which bring about the change of the seasons; the obliquity of the ecliptic; the zodiacal constellations through which the Sun travels, and the periods of the year in which he occupies them, are embraced in Milton's knowledge of the science of astronomy. The motions of the Earth, including the Precession of the Equinoxes; the number and distinctive appearances of the planets, their direct and retrograde courses, and their satellites, are also described by him. The constellations, and their relative positions on the celestial sphere; the principal stars, star-groups, and clusters, and the Galaxy, testify to Milton's knowledge of astronomy, and to the use which he has made of the science in the elaboration of his poem.

The names of fourteen of the constellations are mentioned in 'Paradise Lost.' These, when arranged alphabetically, read as follows:—

Andromeda, Aries, Astrea, Centaurus, Cancer, Capricornus, Gemini, Leo, Libra, Ophiuchus, Orion, Scorpio, Taurus, and Virgo. Milton's allusions to the zodiacal constellations are chiefly associated with his description of the Sun's path in the heavens; but with the celestial sign Libra (the Scales) he has introduced a lofty and poetical conception of the means by which the Creator made known His will when there arose a contention between Gabriel and Satan on his discovery in Paradise.

The Eternal, to prevent such horrid fray, Hung forth in Heaven his golden scales, yet seen Betwixt Astrea[6] and the Scorpion sign, Wherein all things created first he weighed, The pendulous round Earth with balanced air In counterpoise, now ponders all events, Battles and realms. In these he put two weights, The sequel each of parting and of fight: The latter quick up flew, and kicked the beam.—iv. 996-1004.

Orion, the finest constellation in the heavens, did not escape Milton's observation, and there is one allusion to it in his poem. It arrives on the meridian in winter, where it is conspicuous as a brilliant assemblage of stars, and represents an armed giant, or hunter, holding a massive club in his right hand, and having a shield of lion's hide on his left arm. A triple-gemmed belt encircles his waist, from which is suspended a glittering sword, tipped with a bright star. The two brilliants Betelgeux and Bellatrix form the giant's shoulders, and the bright star Rigel marks the position of his advanced foot. The rising of Orion was believed to be accompanied by stormy and tempestuous weather. Milton alludes to this in the following lines:—

When with fierce winds Orion armed Hath vexed the Red Sea coast, whose waves o'erthrew Busiris and his Memphian chivalry.—i. 305-7.

Andromeda is described as being borne by Aries, and in 'Ophiuchus huge' Milton locates a comet which extends the whole length of the constellation. It is evident that Milton possessed a precise knowledge of the configuration and size of the constellations, and of the positions which they occupy relatively to each other on the celestial sphere.

Though Milton was conversant with the Copernican theory, and entertained a conviction of its accuracy and truthfulness, and doubtless recognised the superiority of this system, which, besides conveying to the mind a nobler conception of the universe and of the solar system—though it diminished the importance of the Earth as a member of it—was capable of explaining the occurrence of celestial phenomena in a manner more satisfactory than could be arrived at by the Ptolemaic theory. Notwithstanding this, he selected the Ptolemaic cosmology as the scientific basis upon which he constructed his 'Paradise Lost,' and in its elaboration adhered with marked fidelity to this system. There were many reasons why Milton, in the composition of an imaginative poem, should have chosen the Ptolemaic system of the universe rather than the Copernican. This form of astronomical belief was adopted by all the authors whose works he perused and studied in his younger days, including his favourite poet, Dante; and his own poetic imaginings, as indicated by his early poems, were in harmony with the doctrines of this astronomical creed, a long acquaintance with which had, without doubt, influenced his mind in its favour. This system of revolving spheres, with the steadfast Earth at its centre, and the whole enclosed by the Primum Mobile, constituted a more attractive and picturesque object for poetic description than the simple and uncircumscribed arrangement of the universe expressed by the Copernican theory. It also afforded him an opportunity of localising those regions of space in which the chief incidents in his poem are described—viz. HEAVEN, or THE EMPYREAN, CHAOS, HELL, and the MUNDANE UNIVERSE. Milton's Ptolemaism, with its adjuncts, may be understood by the following:

All that portion of space above the newly created universe, and beyond the Primum Mobile, was known as HEAVEN, or THE EMPYREAN—a region of light, of glory, and of happiness; the dwelling-place of the Deity, Who, though omnipresent, here visibly revealed Himself to all the multitude of angels whom He created, and who surrounded his throne in adoration and worship.

Underneath the universe there existed a vast region of similar dimensions to the Empyrean, called CHAOS, which was occupied by the embryo elements of matter, that with incessant turmoil and confusion warred with each other for supremacy—a wild abyss—

The womb of Nature and perhaps her grave.—ii. 911.

The lower portion of this region was divided off from the remainder, and embraced the locality known as HELL—the place of torment, where the rebellious angels were driven and shut in after their expulsion from Heaven.

As far removed from God and light of Heaven As from the centre thrice to the utmost pole.—i. 73-74.

The NEW UNIVERSE, which included the Earth and all the orbs of the firmament known as the Starry Heavens, was created out of Chaos, and hung, as if suspended by a golden chain, from the Empyrean above; and although its magnitude and dimensions were inconceivable, yet, according to the Ptolemaic theory, it was enclosed by the tenth sphere or Primum Mobile.

By this partitioning of space Milton was able to contrive a system which fulfilled the requirements of his great poem.

The annexed diagram explains the relative positions of the different regions into which space was divided.

Though there are traces of Copernicanism found in 'Paradise Lost,' yet Milton has very faithfully adhered to the Ptolemaic mechanism and nomenclature throughout his poem.

In his description of the Creation, the Earth is formed first, then the Sun, followed by the Moon, and afterwards the stars, all of which are described as being in motion round the Earth. Allusion is also made to this ancient system in several prominent passages, and in the following lines there is a distinct reference to the various revolving spheres.



They pass the planets seven, and pass the fixed, And that crystalline sphere whose balance weighs The trepidation talked, and that first moved.—iii. 481-83.

The seven planetary spheres are first mentioned; then the eighth sphere, or that of the fixed stars; then the ninth, or crystalline, which was believed to cause a shaking, or trepidation, to account for certain irregularities in the motions of the stars; and, lastly, the tenth sphere, or Primum Mobile, called the 'first moved' because it set the other spheres in motion.

To an uninstructed observer, the apparent motion of the heavenly bodies round the Earth would naturally lead him to conclude that, of the two theories, the Ptolemaic was the correct one. We therefore find that Milton adopted the system most in accord with the knowledge and intelligence possessed by the persons portrayed by him in his poem; and in describing the natural phenomena witnessed in the heavens by our first parents, he adheres to the doctrines of the Ptolemaic system, as being most in harmony with the simple and primitive conceptions of those created beings.

To their upward gaze, the orbs of heaven appeared to be in ceaseless motion; the solid Earth, upon which they stood, was alone immovable and at rest. Day after day they observed the Sun pursue his steadfast course with unerring regularity: his rising in the east, accompanied by the rosy hues of morn; his meridian splendour, and his sinking in the west, tinting in colours of purple and gold inimitable the fleecy clouds floating in the azure sky, as he bids farewell for a time to scenes of life and happiness, rejoicing in the light and warmth of his all-cheering beams. With the advent of night they beheld the Moon, now increasing, now waning, pursue her irregular path, also to disappear in the west; whilst, like the bands of an army marshalled in loose array, the constellations of glittering stars, with stately motion, traversed their nocturnal arcs, circling the pole of the heavens.

By referring to Book viii., 15-175, we find an account of an interesting scientific discussion, or conversation, between Adam and Raphael regarding the merits of the Ptolemaic and Copernican systems, and of the relative importance and size of the heavenly bodies. By it we are afforded an opportunity of learning how accurate and precise a knowledge Milton possessed of both theories, and in what clear and perspicuous language he expresses his arguments in favour of or against the doctrines associated with each.

We may, with good reason, regard the views expressed by Adam as representing Milton's own opinions, which were in conformity with the Copernican theory; and in the Angel's reply, though of an undecided character, we are able to perceive how aptly Milton describes the erroneous conclusions upon which the Ptolemaic theory was based.

In this scientific discussion, it would seem rather strange that Adam, the first of men, should have been capable of such philosophic reasoning, propounding, as if by intuition, a theory upon which was founded a system that had not been discovered until many centuries after the time that astronomy became a science. By attributing to Adam such a degree of intelligence and wisdom, the poet has taken a liberty which enabled him to carry on this discussion in a manner befitting the importance of the subject.

In the following lines Adam expresses to his Angel-guest, in forcible and convincing language, his reasons in support of the Copernican theory:—

When I behold this goodly frame, this World, Of Heaven and Earth consisting, and compute Their magnitudes—this Earth, a spot, a grain, An atom, with the Firmament compared And all her numbered stars, that seem to roll Spaces incomprehensible (for such Their distance argues, and their swift return Diurnal) merely to officiate light Round this opacous Earth, this punctual spot, One day and night, in all her vast survey Useless besides—reasoning, I oft admire, How Nature, wise and frugal could commit Such disproportions, with superfluous hand So many nobler bodies to create, Greater so manifold, to this one use, For aught appears, and on their Orbs impose Such restless revolution day by day Repeated, while the sedentary Earth, That better might with far less compass move, Served by more noble than herself, attains Her end without least motion, and receives, As tribute, such a sumless journey brought Of incorporeal speed, her warmth and light; Speed, to describe whose swiftness number fails.—viii. 15-38.

We are enabled to perceive that Milton had formed a correct conception of the magnitude and proportions of the universe, and also of the relative size and importance of the Earth, which he describes as 'a spot, a grain, an atom,' when compared with the surrounding heavens. He expresses his surprise that all the stars of the firmament, whose distances are so remote, and whose dimensions so greatly exceed those of this globe, should in their diurnal revolution have 'such a sumless journey of incorporeal speed imposed upon them' merely to officiate light to the Earth, 'this punctual spot;' and reasoning, wonders how Nature, wise and frugal in her ways, should commit such disproportions, by adopting means so great to accomplish a result so small, when motion imparted to the sedentary Earth would with greater ease produce the same effect.

The inconceivable velocity with which it would be necessary for those orbs to travel in order to accomplish a daily revolution round the Earth might be described as almost spiritual, and beyond the power of calculation by numbers.

The Angel, after listening to Adam's argument, expresses approval of his desire to obtain knowledge, but answers him dubiously, and at the same time criticises in a severe and adverse manner the Ptolemaic theory.

To ask or search I blame thee not; for Heaven Is as the Book of God before thee set, Wherein to read his wondrous works, and learn His seasons, hours, or days, or months, or years. This to attain, whether Heaven move or Earth, Imports not, if thou reckon right; the rest From Man or Angel the Great Architect Did wisely to conceal, and not divulge His secrets, to be scanned by them who ought Rather admire. Or, if they list to try Conjecture, he his fabric of the Heavens Hath left to their disputes, perhaps to move His laughter at their quaint opinions wide Hereafter, when they come to model Heaven, And calculate the stars; how they will wield The mighty frame; how build, unbuild, contrive To save appearances; how gird the Sphere With Centric and Eccentric scribbled o'er Cycle and Epicycle, Orb in Orb.—viii. 66-84.

When, with the advancement of science, astronomical observations were made with greater accuracy, it was discovered that uniformity of motion was not always maintained by those bodies which were believed to move in circles round the Earth. It was observed that the Sun, when on one side of his orbit, had an accelerated motion, as compared with the speed at which he travelled when on the other side. The planets, also, appeared to move with irregularity: sometimes a planet was observed to advance, then become stationary, and afterwards affect a retrograde movement. Those inequalities of motion could not be explained by means of the revolution of crystalline spheres alone, but were accounted for by imagining the existence of a small circle, or epicycle, whose centre corresponded with a fixed point in the larger circle, or eccentric, as it was called. This small circle revolved on its axis when carried round with the larger one, and round it the planet also revolved, which when situated in its outer portion would have a forward, and when in its inner portion a retrograde, motion.

The theory of eccentrics and epicycles was sufficient for a time to account for the inequalities of motion already described, and by this means the Ptolemaic system was enabled to retain its ascendency for a longer period than it otherwise would have done. But more recent discoveries brought to light discrepancies and difficulties which were explained away by adding epicycle to epicycle. This created a most complicated entanglement, and hastened the downfall of a system which, after an existence of many centuries, sank into oblivion, and is now remembered as a belief of bygone ages.

The devices which the upholders of this system were compelled to adopt, in order 'to save appearances,' with 'centric and eccentric,' cycle and epicycle, 'orb in orb,' are in this manner appropriately described by Milton, as indicating the confusion arising from a theory based upon false hypotheses.

Continuing his reply, the Angel says:—

Already by thy reasoning this I guess, Who art to lead thy offspring, and supposest That bodies bright and greater should not serve The less not bright, nor Heaven such journies run, Earth sitting still, when she alone receives The benefit. Consider, first, that great Or bright infers not excellence. The Earth, Though, in comparison of Heaven, so small, Nor glistering, may of solid good contain More plenty than the Sun that barren shines, Whose virtue on itself works no effect, But in the fruitful Earth; there first received, His beams, inactive else, their vigour find, Yet not to Earth are those bright luminaries Officious, but to thee, Earth's habitant. And, for the Heaven's wide circuit, let it speak The Maker's high magnificence, who built So spacious, and his line stretched out so far, That Man may know he dwells not in his own— An edifice too large for him to fill, Lodged in a small partition; and the rest Ordained for uses to his Lord best known, The swiftness of those Circles attribute, Though numberless, to his Omnipotence, That to corporeal substances could add Speed almost spiritual. Me thou think'st not slow, Who since the morning-hour set out from Heaven Where God resides, and ere midday arrived In Eden—distance inexpressible By numbers that have name. But this I urge, Admitting motion in the Heavens, to show Invalid that which thee to doubt it moved; Not that I so affirm, though so it seem To thee who hast thy dwelling here on Earth. God, to remove his ways from human sense, Placed Heaven from Earth so far, that earthly sight, If it presume, might err in things too high, And no advantage gain.—viii. 85-122.

Notwithstanding the Angel's severe criticism of the Ptolemaic system, he does not unreservedly support the conclusions arrived at by Adam, but endeavours to show that his reasoning may not be altogether correct. He questions the validity of his argument that bodies of greater size and brightness should not serve the smaller, though not bright, and that heaven should move, while the Earth remained at rest. He argues that great or bright infers not excellence, and that the Earth, though small, may contain more virtue than the Sun, that 'barren shines,' whose beams create no beneficial effect, except when directed on the fruitful Earth. He reminds Adam that those bright luminaries minister not to the Earth, but to himself, 'Earth's habitant,' and directs his attention to the magnificence and extent of the surrounding universe, of which he occupies but a small portion. The diurnal swiftness of the orbs that move round the Earth he attributes to God's omnipotence, that to material bodies 'could add speed almost spiritual.'

The Angel, after alluding to his rapid flight through space, suggests that God placed heaven so far from Earth that man might not presume to inquire into things which it would be of no advantage for him to know. He then suddenly changes to the Copernican system, which he lucidly describes in the following lines:—

What if the Sun Be centre to the World, and other stars By his attractive virtue and their own Incited, dance about him various rounds? Their wandering course, now high, now low, then hid, Progressive, retrograde, or standing still, In six thou seest; and what if, seventh to these The planet Earth, so steadfast though she seem, Insensibly three different motions move? Which else to several spheres thou must ascribe, Moved contrary with thwart obliquities, Or save the Sun his labour, and that swift Nocturnal and diurnal rhomb supposed Invisible else above all stars, the wheel Of day and night; which needs not thy belief, If Earth, industrious of herself, fetch day Travelling east, and with her part averse From the Sun's beam meet night, her other part Still luminous by his ray. What if that light, Sent from her through the wide transpicuous air, To the terrestrial Moon be as a star, Enlightening her by day, as she by night This Earth—reciprocal, if land be there, Fields and inhabitants? Her spots thou seest As clouds, and clouds may rain, and rain produce Fruits in her softened soil, for some to eat Allotted there; and other Suns, perhaps, With their attendant Moons, thou wilt descry, Communicating male and female light— Which two great sexes animate the World, Stored in each orb perhaps with some that live. For such vast room in Nature unpossessed By living soul, desert and desolate, Only to shine, yet scarce to contribute Each orb a glimpse of light, conveyed so far Down to this habitable, which returns Light back to them, is obvious to dispute.—viii. 122-58.

The Copernican theory, which is less complicated and more easily understood than the Ptolemaic, is described by Milton with accuracy and methodical skill.

The Sun having been assigned that central position in the system which his magnitude and importance claim as his due, the planets circling in orbits around him have their motions described in a manner indicative of the precise knowledge which Milton acquired of this theory. At this time the law of gravitation was unknown, and, although the ellipticity of the orbits of the planets had been discovered by Kepler, the nature of the motive force which guided and retained them in their paths still remained a mystery. It was believed that the planets were whirled round the Sun, as if by the action of magnetic fibres; a mutual attractive influence having been supposed to exist between them and the orb, similar to that of the opposite poles of magnets.

Milton alludes to this theory in the following lines:—

They, as they move Their starry dance in numbers that compute Days, months, and years, towards his all-cheering lamp Turn swift their various motions, or are turned By his magnetic beam.—iii. 579-83.

An important advance upon this theory was made by Horrox, who, in his study of celestial dynamics, attributed the curvilineal motion of the planets to the influence of two forces, one projective, the other attractive. He illustrated this by observing the path described by a stone when thrown obliquely into the air. He perceived that its motion was governed by the impulse imparted to it by the hand, and also by the attractive force of the Earth. Under these two influences, the stone describes a graceful curve, and in its descent falls at the same angle at which it rose. Hence arises the general law: 'When two spheres are mutually attracted, and if not prevented by foreign influences, their straight paths are deflected into curves concave to each other, and corresponding with one of the sections of a cone, according to the velocity of the revolving body. If the velocity with which the revolving body is impelled be equal to what it would acquire by falling through half the radius of a circle described from the centre of deflection, its orbit will be circular; but if it be less than that quantity, its path becomes elliptical.'

Newton afterwards embraced this law in his great principle of gravitation, and demonstrated that the force which guides and retains the Earth and planets in their orbits resides in the Sun. By the orb's attractive influence a planet, after having received its first impulse, is deflected from its original straight path, and bent towards that luminary, and by the combined action of the projective and attractive forces is made to describe an orbit which, if elliptical, has one of its foci occupied by the Sun. So evenly balanced are those two forces, that one is unable to gain any permanent ascendency over the other, and consequently the planet traverses its orbit with unerring regularity, and, if undisturbed by external influences, will continue in its path for all time.

Milton describes the position of the planets in the sky as—

Now high, now low, then hid;

and their motions—

Progressive, retrograde, or standing still.

It is evident that Milton was familiar with the apparently irregular paths pursued by the planets when observed from the Earth. He knew of their stationary points, and also the backward loopings traced out by them on the surface of the sphere.

If observed from the Sun, all the planets would be seen to follow their true paths round that body; their motion would invariably lie in the same direction, and any variation in their speed as they approached perihelion or aphelion would be real. But the planets, when observed from the Earth, which is itself in motion, appear to move irregularly. Sometimes they remain stationary for a brief period, and, instead of progressing onward, affect a retrograde movement. This irregularity of motion is only apparent, and can be explained as a result of the combined motions of the Earth and planets, which are travelling together round the Sun with different velocities, and in orbits of unequal magnitude.

In his allusion to the Copernican system the 'planet' 'Earth' is described by Milton as seventh. This is not strictly accurate, as only five planets were known—viz. Mercury, Venus, Mars, Jupiter, and Saturn; but to make up the number Milton has included the Moon, which may be regarded as the Earth's planet.

The three motions ascribed to the Earth are—(1) The diurnal rotation on her axis; (2) her annual revolution round the Sun; (3) Precession of the Equinoxes.

The rotation of the Earth on her axis may be likened to the spinning motion of a top, and is the cause of the alternation of day and night. This rotatory motion is sustained with such exact precision that, during the past 2,000 years, it has been impossible to detect the minutest difference in the time in which the Earth accomplishes a revolution on her axis, and therefore the length of the sidereal day, which is 3 minutes 56 seconds shorter than the mean solar day, is invariable. In this motion of the Earth we have a time-measuring unit which may be regarded as absolutely correct.

The Earth completes a revolution of her orbit in 365-1/4 days. In this period of time she accomplishes a journey of 580 millions of miles, travelling at the average rate of 66,000 miles an hour. The change of the seasons, and the lengthening and shortening of the day, are natural phenomena, which occur as a consequence of the Earth's annual revolution round the Sun. Precession is a retrograde or westerly motion of the equinoctial points, caused by the attraction of the Sun, Moon, and planets on the spheroidal figure of the Earth. By this movement the poles of the Earth are made to describe a circular path in that part of the heavens to which they point; so that, after the lapse of many years, the star which is known as the Pole Star will not occupy the position indicated by its name, but will be situated at a considerable distance from the pole. These motions, Milton says, unless attributed to the Earth, must be ascribed to several spheres crossing and thwarting each other obliquely; but the Earth, by rotating from west to east, will of herself fetch day, her other half, averted from the Sun's rays, being enveloped in night. Thus saving the Sun his labour, and the 'primum mobile,' 'that swift nocturnal and diurnal rhomb,' which carried all the lower spheres along with it, and brought about the change of day and night.

Milton's allusion to the occurrence of natural phenomena in the Moon similar to those which happen on the Earth is in keeping with the opinions entertained regarding our satellite, Galileo having imagined that he discovered with his telescope continents and seas on the lunar surface, which led to the belief that the Moon was the abode of intelligent life.

... and other suns, perhaps, With their attendant moons, thou wilt descry Communicating male and female light.—viii. 148-50.

Milton in these lines refers to Jupiter and Saturn, and their satellites, which had been recently discovered; those of the former by Galileo, and four of those of the latter by Cassini. The existence of male and female light was an idea entertained by the ancients, and which is mentioned by Pliny. The Sun was regarded as a masculine star, and the Moon as feminine; the light emanating from each being similarly distinguished, and possessing different properties.

Milton supposes that, as the Earth receives light from the stars, she returns light back to them. But in his time little was known about the stars, nor was it ascertained how distant they are.

The Angel, in bringing to a conclusion his conversation with Adam, deems it unadvisable to vouchsafe him a decisive reply to his inquiry regarding the motions of celestial bodies, and in the following lines gives a beautifully poetical summary of this elevated and philosophic discussion:—

But whether thus these things, or whether not, Whether the Sun, predominant in Heaven, Rise on the Earth, or Earth rise on the Sun; He from the east his flaming round begin, Or she from west her silent course advance With inoffensive pace that spinning sleeps On her soft axle, whilst she paces even, And bears thee soft with the smooth air along— Solicit not thy thoughts with matters hid.—viii. 159-67.

In this scientific discourse between Adam and Raphael, in which they discuss the structural arrangement of the heavens and the motions of celestial bodies, we are afforded an opportunity of learning what exact and comprehensive knowledge Milton possessed of both the Ptolemaic and Copernican theories. The concise and accurate manner in which he describes the doctrines belonging to each system indicates that he must have devoted considerable time and attention to making himself master of the details associated with both theories, which in his time were the cause of much controversy and discussion among philosophers and men of science.

The Ptolemaic system, with its crystalline spheres revolving round the Earth, the addition to those of cycles and epicycles, and the heaping of them upon each other, in order to account for phenomena associated with the motions of celestial bodies, are concisely and accurately described.

The unreasonableness of this theory, when compared with the Copernican, is clearly delineated by Milton where Adam is made to express his views with regard to motion in the heavens. His argument, declared in logical and persuasive language, demonstrates how contrary to reason it would be to imagine that the entire heavens should revolve round the Earth to bring about a result which could be more easily attained by imparting motion to the Earth herself. The inconceivable velocity with which it would be necessary for the celestial orbs to travel in order to accomplish their daily revolution is described by him as opposed to all reason, and entailing upon them a journey which it would be impossible for material bodies to perform. None the less accurate is Milton's description of the Copernican system. He describes the Sun as occupying that position in the system which his magnitude and supreme importance claim as his sole right, having the planets with their satellites,

That from his lordly eye keep distance due.—iii. 578,

circling in majestic orbits around him, acknowledging his controlling power, and bending to his firm but gentle sway. Their positions, their paths, and their motions, real and apparent, are described in flowing and harmonious verse.



CHAPTER IV

MILTON AND GALILEO

After the death of his mother, which occurred in 1637, Milton expressed a desire to visit the Continent, where there were many places of interest which he often longed to see. Having obtained the consent of his kind and indulgent father, he set out on his travels in April 1638, accompanied by a single man-servant, and arrived in Paris, where he only stayed a few days. During his residence in the French capital he was introduced by Lord Scudamore, the English Ambassador at the Court of Versailles, to Hugo Grotius, one of the most distinguished scholars and philosophic thinkers of his age. From Paris Milton journeyed to Nice, where he first beheld the beauty of Italian scenery and the classic shores of the Mediterranean Sea. From Nice he sailed to Genoa and Leghorn, and after a short stay at those places continued his journey to Florence, one of the most interesting and picturesque of Italian cities. Situated in the Valley of the Arno, and encircled by sloping hills covered with luxuriant vegetation, the sides of which were studded with residences half-hidden among the foliage of gardens and vineyards, Florence, besides being famed for its natural beauty, was at that time the centre of Italian culture and learning, and the abode of men eminent in literature and science. Here Milton remained for a period of two months, and enjoyed the friendship and hospitality of its most noted citizens, many of whom delighted to honour their English visitor. He was warmly welcomed by the members of the various literary academies, who admired his compositions and conversation; the flattering encomiums bestowed upon him by those learned societies having been amply repaid by Milton in choice and elegant Latin verse.

Among those who resided in the vicinity of Florence was the illustrious Galileo, who in his sorrow-stricken old age was held a prisoner of the Inquisition for having upheld and taught scientific doctrines which were declared to be heretical. After his abjuration he was committed to prison, but on the intervention of influential friends was released after a few days' incarceration, and permitted to return to his home at Arcetri. He was, however, kept under strict surveillance, and forbidden to leave his house or receive any of his intimate friends without having first obtained the sanction of the ecclesiastical authorities. After several years of close confinement at Arcetri, during which time he suffered much from rheumatism and continued ill-health, aggravated by grief and mental depression consequent upon the death of his favourite daughter, Galileo applied for permission to go to Florence in order to place himself under medical treatment. This request was granted by the Pope subject to certain conditions, which would be communicated to him when he presented himself at the office of the Inquisition at Florence. These were more severe than he anticipated. He was forbidden to leave his house or receive any of his friends there, and those injunctions were so strictly adhered to that during Passion Week he had to obtain a special order so that he might be able to attend mass. At the expiration of a few months Galileo was ordered to return to Arcetri, which he never left again.

An affliction, perhaps the most deplorable that can happen to any human being, was added to the burden of Galileo's misfortunes and woes. A disorder which had some years previously injured the sight of his right eye returned in 1636. In the following year the left eye became similarly affected, with the result that in a few months Galileo became totally blind. His friends at first hoped that the disease was cataract, and that some relief might be afforded by means of an operation; but it was discovered to be an opacity of the cornea, which at his age was considered unamenable to treatment. This sudden and unexpected calamity was to Galileo a most deplorable occurrence, for it necessitated the relinquishment of his favourite pursuit, which he followed with such intense interest and delight. His friend Castelli writes: 'The noblest eye is darkened which Nature ever made; an eye so privileged, and gifted with such rare qualities that it may with truth be said to have seen more than all of those eyes who are gone, and to have opened the eyes of all who are to come.' Galileo endured his affliction with patient resignation and fortitude, and in the following extract from a letter by him he acknowledges the chastening hand of a Divine Providence: 'Alas! your dear friend and servant Galileo has become totally blind, so that this heaven, this earth, this universe, which with wonderful observations I had enlarged a hundred and a thousand times beyond the belief of bygone ages, henceforward for me is shrunk into the narrow space which I myself fill in it. So it pleases God; it shall then please me also.' The rigorous curtailment of his liberty which prompted Galileo to head his letters, 'From my prison at Arcetri,' was relaxed when total blindness had supervened upon the infirmities of age. Permission was given him to receive his friends, and he was allowed to have free intercourse with his neighbours.

Milton, during his stay at Florence, visited Galileo at Arcetri. We are ignorant of the details of this eventful and interesting interview between the aged and blind astronomer and the young English poet, who afterwards immortalised his name in heroic verse, and who in his declining years suffered from an affliction similar to that which befel Galileo, and to which he alludes so pathetically in the following lines:—

Thee I revisit safe, And feel thy sovran vital lamp; but thou Revisitest not these eyes, that roll in vain To find thy piercing ray, and find no dawn; So thick a drop serene hath quenched their orbs, Or dim suffusion veiled.—iii. 21-26.

We can imagine that Galileo's astronomical views, which at that time were the subject of much discussion among scientific men and professors of religion, and on account of which he suffered persecution, were eagerly discussed. It is also probable that the information communicated by Galileo, or by some of his followers, may have persuaded Milton to entertain a more favourable opinion of the Copernican theory. The interesting discoveries made by Galileo with his telescope without doubt formed a pleasant subject of conversation, and Milton enjoyed the privilege of listening to a detailed description of these from the lips of the aged astronomer. The telescope, its principle, its mechanism, and the method of observing, were most probably explained to him; and we can believe that an opportunity was afforded him of examining those in Galileo's observatory, and of perhaps testing their magnifying power upon some celestial object favourably situated for observation. Though Milton has not favoured us with any details of his visit to Galileo, yet it was one which made a lasting impression upon his mind, and was never afterwards forgotten by him. 'There it was,' he writes, 'I found and visited the famous Galileo, grown old, a prisoner of the Inquisition for thinking in astronomy otherwise than the Franciscan and Dominican licensers thought.' In years long after, when Milton, himself feeble and blind, sat down to compose his 'Paradise Lost,' the remembrance of the Tuscan artist and his telescope was still fresh in his memory.

By the invention of the telescope and its application to astronomical research, a vast amount of information and additional detail have been learned regarding the bodies which enter into the formation of the solar system; and by its aid many new ones were also discovered. On sweeping the heavens with the instrument, the illimitable extent of the sidereal universe became apparent, and numberless objects of interest were brought within the range of vision the existence of which had not been previously imagined.

The Galilean telescope was invented in 1609. But the magnifying power of certain lenses, and their combination in producing singular visual effects, are alluded to in the writings of several early authors. The value of single lenses as an aid to sight had been long known, and spectacles were in common use in the fourteenth century. Several mathematicians have described the wonderful optical results obtained from glasses concave and convex, of parabolic and circular forms, and from 'perspective glasses,' in which were embodied the principle of the telescope. It is asserted that our countryman, Roger Bacon (1214), had some notion of the properties of the telescope; but among those familiar with the combination of lenses the two men who made the nearest approach to the invention of the instrument were Baptista Porta and Gerolamo Fracastro. The latter, who died in 1553, writes as follows: 'For which reason those things which are seen at the bottom of water appear greater than those which are at the top; and if anyone look through two eye-glasses, one placed upon the other, he will see everything much larger and nearer.' It is doubtful if Fracastro had any notion of constructing a mechanism which might answer the purpose of a telescopic tube. Baptista Porta (1611) is more explicit in what he describes. He writes: 'Concave lenses show distant objects most clearly, convex those which are nearer; whence they may be used to assist the sight. With a concave glass distant objects will be seen, small, but distinct; with a convex one, those near at hand, larger, but confused; if you know rightly how to combine one of each sort, you will see both far and near objects larger and clearer.' He then goes on to say: 'I shall now endeavour to show in what manner we may continue to recognise our friends at the distance of several miles, and how those of weak sight may read the most minute letters from a distance. It is an invention of great utility, and grounded on optical principles; nor is at all difficult of execution; but it must be so divulged as not to be understood by the vulgar, and yet be clear to the sharp-sighted.' After this, he proceeds to describe a mechanism the details of which are confusing and unintelligible, nor did it appear to bear any resemblance to a telescopic tube.

In a work published by Thomas Digges in 1591, he makes the following allusion to his father's experiments with the lenses: 'My father, by his continuall painfull practices, assisted with demonstrations mathematicall, was able, and sundry times hath by proportionall glasses, duely situate in convenient angles, not only discouered things farre off, read letters, numbered peeces of money with the verye coyne and superscription thereof cast by some of his freends of purpose, upon downes in open fields; but also seuen miles off, declared what hath beene doone at that instant in priuate places.' It must be admitted that if Leonard Digges had not constructed a telescope, he knew how to combine lenses by the aid of which a visual effect was created similar to that produced by the use of the instrument.

The inventor of the telescope was a Dutchman named Hans Lippershey, who carried on the business of a spectacle-maker in the town of Middelburg. His discovery was purely accidental. It is said that the instrument—which was directed towards a weather-cock on a church spire, of which it gave a large and inverted image—was for some time exhibited in his shop as a curiosity before its importance was recognised. The Marquis Spinola, happening to see this philosophical toy, purchased it, and presented it to Prince Maurice of Nassau, who imagined it might be of service for the purpose of military reconnoitring. The value of the invention was, however, soon realised, and in the following year telescopes were sold in Paris. In 1609, Galileo, when on a visit to a friend at Venice, received intelligence of the invention of an instrument by a Dutch optician which possessed the power of causing distant objects to appear much nearer than when observed by ordinary vision. The accuracy of this information was confirmed by letters which he received from Paris; and this general report, Galileo asserted, was all he knew of the subject. Fuccarius, in a disparaging letter, says that one of the Dutch telescopes had been brought to Venice, and that he himself had seen it. This statement is not incompatible with Galileo's affirmation that he had not seen the original instrument, and knew no more about it than what had been communicated to him in the letters from the French capital. It was insinuated by Fuccarius that Galileo had seen the telescope at Venice, but, as he denied this, we should not hesitate to believe in his veracity.

Immediately after his return to Padua, Galileo began to think how he might be able to contrive an instrument with properties similar to the one of which he had been informed; and in the following words describes the process of reasoning by which he arrived at a successful result: 'I argued in the following manner. The contrivance consists either of one glass or of more—one is not sufficient, since it must be either convex, concave, or plane. The last does not produce any sensible alteration in objects; the concave diminishes them. It is true that the convex magnifies, but it renders them confused and indistinct; consequently, one glass is insufficient to produce the desired effect. Proceeding to consider two glasses, and bearing in mind that the plane causes no change, I determined that the instrument could not consist of the combination of a plane glass with either of the other two. I therefore applied myself to make experiments on combinations of the two other kinds, and thus obtained that of which I was in search.' Galileo's telescope consisted of two lenses—one plano-convex, the other plano-concave, the latter being held next the eye. These he fixed in a piece of organ pipe, which served the purpose of a tube, the glasses being distant from each other by the difference of their focal lengths. An exactly similar principle is adopted in the construction of an opera-glass, which can be accurately described as a double Galilean telescope. Galileo must be regarded as the inventor of this kind of telescope, which in one respect differed very materially from the one constructed by the Dutch optician. If what has been said with regard to the inverted weather-cock be true, then Lippershey's telescope was made with two convex lenses, distant from each other by the sum of their focal lengths, and all objects observed with it were seen inverted. Refracting astronomical telescopes are now constructed on this principle, it having been discovered that for observational purposes they possess several advantages over the Galilean instrument. When Galileo had completed his first telescope he returned with it to Venice, where he exhibited it to his friends. The sensation created by this small instrument, which magnified only three times, was most extraordinary, and almost amounted to a frenzy. Crowds of the principal citizens of Venice flocked to Galileo's house in order that they might see the magical tube about which such wonderful reports were circulated; and for upwards of a month he was daily occupied in describing his invention to attentive audiences. At the expiration of this time the Doge of Venice, Leonardo Deodati, hinted that the Senate would not be averse to receive the telescope as a gift. Galileo readily acquiesced with this desire, and, as an acknowledgment of his merits, a decree was issued confirming his appointment as professor at Padua for life, and increasing his salary from 500 to 1,000 florins. The public excitement created by the telescope showed no signs of abatement. Sirturi mentions that, having succeeded in constructing an instrument, he ascended the tower of St. Mark's at Venice, hoping to be able to use it there without interruption. He was, however, detected by a few individuals, and soon surrounded by a crowd, which took possession of his telescope, and detained him for several hours until their curiosity was satisfied. Eager inquiries having been made as to where he lodged, Sirturi, fearing a repetition of his experience in the church tower, decided to quit Venice early next morning, and betake himself to a quieter and less frequented neighbourhood.

The instrument was at first called Galileo's tube; the double eye-glass; the perspective; the trunk; the cylinder. The appellation telescope was given it by Demisiano.

Galileo next directed his attention to the construction of telescopes, and applied his mechanical skill in making instruments of a larger size, one of which magnified eight times. 'And at length,' he writes, 'sparing neither labour nor expense, he completed an instrument that was capable of magnifying more than thirty times.'

Galileo now commenced an exploration of the celestial regions with his telescope, and on carefully examining some of the heavenly bodies, made many wonderful discoveries which added greatly to the fame and lustre of his name.

The first celestial object to which Galileo directed his telescope was the Moon. He was deeply interested to find how much her surface resembled that of the Earth, and was able to perceive lofty mountain ranges, the illumined peaks of which reflected the sunlight, whilst their bases and sides were still enveloped in dark shadow; great plains which he imagined were seas, valleys, elevated ridges, depressions, and inequalities similar to what are found on our globe. Galileo believed the Moon to be a habitable world, and concluded that the dark and luminous portions of her surface were land and water, which reflected with unequal intensity the light of the Sun. The followers of Aristotle received the announcement of these discoveries with much displeasure. They maintained that the Moon was perfectly spherical and smooth—a vast mirror, the dark portions of which were the reflection of our terrestrial mountains and forests—and accused Galileo 'of taking a delight in distorting and ruining the fairest works of Nature.' He appealed to the unequal condition of the surface of our globe, but this was of no avail in altering their preconceived notions of the lunar surface.

Perhaps the most important discovery made by Galileo with the telescope was that of the four moons of Jupiter. On the night of January 7, 1610, when engaged in observing the planet, his attention was attracted by three small stars which appeared brighter than those in their immediate neighbourhood. They were all in a straight line and parallel with the ecliptic; two of them were situated to the east, and one to the west of Jupiter. On the following night he was surprised to find all three to the west of the planet, and nearer to each other. This caused him considerable perplexity, and he was at a loss to understand how Jupiter could be east of the three stars, when on the preceding night he was observed to the west of two of them. Galileo was unable to reconcile the altered positions of those bodies with the apparent motion of Jupiter among the fixed stars as indicated by the astronomical tables. The next opportunity he had of observing them was on the 10th, when two stars only were visible, and they were to the east of the planet. As it was impossible for Jupiter to move from west to east on January 8 and from east to west on the 10th, he concluded that it was the motion of the stars and not that of Jupiter which accounted for the observed phenomena. Galileo watched the stars attentively on successive evenings and discovered a fourth, and on observing how they changed their positions relatively to each other he soon arrived at the conclusion that the stars were four moons which revolved round Jupiter after the manner in which the Moon revolves round the Earth. Having assured himself that the four new stars were four moons that with periodical regularity circled round the great planet, Galileo named them the Medicean Stars in honour of his patron, Cosmo de' Medici, Grand Duke of Tuscany. He also published an essay entitled 'Nuncius Sidereus,' or the 'Sidereal Messenger,' which contained an account of this important discovery.

The announcement of Galileo's discovery of the four satellites of Jupiter created a profound sensation, and its significance became at once apparent. Aristotelians and Ptolemaists received the information with much disfavour and incredulity, and many persons positively refused to believe Galileo, whom they accused of inventing fables. On the other hand, the upholders of the Copernican theory hailed it with satisfaction, as it declared that Jupiter with his four moons constituted a system of greater magnitude and importance than that of our globe with her single satellite, and that consequently the Earth could not be regarded as the centre of the universe.

When Kepler heard of this remarkable discovery, he wrote to Galileo and expressed himself in the following characteristic manner: 'I was sitting idle at home thinking of you, most excellent Galileo, and your letters, when the news was brought me of the discovery of four planets by the help of the double eye-glass. Wachenfels stopped his carriage at my door to tell me, when such a fit of wonder seized me at a report which seemed so very absurd, and I was thrown into such agitation at seeing an old dispute between us decided in this way, that between his joy, my colouring, and the laughter of both, confounded as we were by such a novelty, we were hardly capable, he of speaking, or I of listening.... I am so far from disbelieving in the existence of the four circumjovial planets, that I long for a telescope to anticipate you, if possible, in discovering two round Mars (as the proportion seems to me to require), six or eight round Saturn, and perhaps one each round Mercury and Venus.' The intelligence of Galileo's discoveries was received by his opponents in a spirit entirely different from that manifested by Kepler. The principal professor of philosophy at Padua, when requested to look at the Moon and planets through Galileo's glass, persistently declined, and did his utmost to persuade the Grand Duke that the four satellites of Jupiter could not possibly exist. Francesco Sizzi, a Florentine astronomer, argued that, as there are seven apertures in the head, seven known metals, and seven days in the week, so there could only be seven planets. To these absurd remarks Galileo replied by saying that, 'whatever their force might be as a reason for believing beforehand that no more than seven planets would be discovered, they hardly seemed of sufficient weight to destroy the new ones when actually seen.' Another individual, named Christmann, writes: 'We are not to think that Jupiter has four satellites given him by Nature in order, by revolving round him, to immortalize the name of the Medici, who first had notice of the observation. These are the dreams of idle men, who love ludicrous ideas better than our laborious and industrious correction of the heavens. Nature abhors so horrible a chaos, and to the truly wise such vanity is detestable.' Martin Horky, a protege of Kepler's, issued a pamphlet in which he made a violent attack on Galileo. He says: 'I will never concede his four new planets to that Italian from Padua though I die for it.' He then asks the following questions, and replies to them himself: (1) Whether they exist? (2) What they are? (3) What they are like? (4) Why they are? 'The first question is soon disposed of by Horky's declaring positively that he has examined the heavens with Galileo's own glass, and that no such thing as a satellite about Jupiter exists. To the second, he declared solemnly that he does not more surely know that he has a soul in his body than that reflected rays are the sole cause of Galileo's erroneous observations. In regard to the third question, he says that these planets are like the smallest fly compared to an elephant; and, finally, concludes on the fourth, that the only use of them is to gratify Galileo's "thirst of gold," and to afford himself a subject of discussion.'[7] Galileo did not condescend to take any notice of this scurrilous production; but Horky, who imagined that he had done something clever, sent a copy of his pamphlet to Kepler. In a few days after he called to see him, and was received with such a storm of indignation that he begged for mercy and implored his forgiveness. Kepler forgave him, but insisted on his making amends. He writes: 'I have taken him again into favour upon this preliminary condition, to which he has agreed—that I am to show him Jupiter's satellites, and he is to see them, and own that they are there.'