Visionary Of Stellar Systems

''Who in England is so peculiar as to be bothered by the apparent irregularity of the Milky Way!''

Abraham Gotthelf Kaestner, unsympathetic reviewer of Wright's book, An Original Theory or New Hypothesis of the Universe, 17521

On a damp and windy night in September 1729, around the time of his eighteenth birthday, Thomas Wright ran away from his first job as an apprentice. Scandalous rumors about his involvement with a young woman buzzed about the northern English town of Bishop Auckland. Wright had pleaded his case, but could not convince his master, clock- and watchmaker Bryan Stobart, of his innocence. So, clutching the astronomy books he had spent most of his pocket money on, Wright picked his way across the fields west of town, ''intending for Ireland'' as he wrote in his journal, and trying to avoid stumbling into treacherous pit-holes left by coal miners.2

Wright was in a pickle, and not for the first or last time. His great talents and originality would secure him a place in the history of astronomy; his drawings would adorn astronomy textbooks more than 200 years after his death. But his intellectual and emotional intensity made it difficult for him to settle down and find his niche in society. On a recent trip home, when he was recovering from a broken collar-bone and reading all the astronomy books he could buy or borrow, his father had grown impatient with his zealous study and burned all the books he could find. His mother subsequently supplied him with money for books, but Wright, in his impetuous flight across the fells and away from the scandal behind him, didn't feel like going back to take refuge at home in Byer's Green, only a few miles away.

Fortunately for the runaway, he soon encountered a kindly miller with a comfortable guest bed in his mill. By sunrise the next morning, when the miller filled his pockets with bread and cheese, Wright was reconsidering his original plan to make for the west coast and sail for Ireland. The next day he presented himself at his father's friend's house in Sunderland, a port on the east coast, ''inexpressibly weary and fatigued'' after walking more than 60 miles. ''Next day writ to my father,'' he recorded in his journal, ''and to my great joy was sent for Home.''3

Thomas Wright (figure 3.1) was born 22 September 1711 in the village of Byer's Green not far from the town of Durham.

Figure 3.1 Thomas Wright (1711-1786). (Reproduced by permission of the British Library.)

His family included two older brothers and at least one sister, also older than he. His father John owned a small parcel of land and thus enjoyed the status of yeoman, or independent farmer, but earned a living primarily as a carpenter. Wright's mother Margaret we know little about. She probably had some education as a child, for her sister Mary grew up to become headmistress of a boarding school in Yorkshire. Wright described Mary as ''a very great Scholer but not Rich.''4

To the delight of historians, Wright confided details of his life and work in a journal, which passed to a friend after his death and eventually found its way, along with other Wright manuscripts, to the British Library. Wright's brief but frank descriptions of his circumstances and motivations help shed light on the development of his ideas about the structure of the universe. They also reveal the character of a man who was not a professional astronomer either by our standards or by those of his day, but who had a significant insight into the three-dimensional arrangement of the stars of the Milky Way system.

The friend who acquired Wright's journal, George Allen, did modify Wright's text in one way, which makes some of the quotations from the journal in this chapter confusing: in preparing a biographical note about Wright for the Gentleman's Magazine, Allen went through the text and generally, though not always, over-wrote the first-person pronouns to change them to the third person. Thus Wright's description of the scandal that drove him from Bishop Aukland reads, in part, ''Soon she came to Bed to him upon which fearing the consequence of Forfeitin[g] his Indentures ec [etc.] left her and complain'd, upon which the Man swore to be the death of him.'' The original text said ''me'' and ''my'' in place of ''him'' and ''his.''5

We learn from Wright that as a child he was ''Very wild & much adicted [to] Sport.'' He attended a community-supported or ''private'' school from the age of 4 or 5, then a tuition fee-charging or ''public'' school, where he studied Latin. However, he notes under the heading 1719, when he was 7 or 8, that he was obliged to leave the Latin school, ''being interrupted by a very great Impediment of Speach.''6

Wright's sister taught him arithmetic and writing for a while. She evidently did not make much headway with his writing style, which is not noteworthy, but Wright's talents in mathematics must have appeared at this time, for his family enlisted the help of a tutor. Wright notes that he studied with a local man by the name of Thomas Munday, ''a wrgt [right] good Accomptant and an Astronomer.'' An entry opposite the date 1723 says in his typically brief style, ''Much in love with Mathematicks.''7

When Wright was 13, his father bound him as an indentured apprentice to the watchmaker Bryan Stobart. Normally such a contract would have lasted seven years, until the apprentice was about 21 years old, and ready to become a journeyman. During Wright's abbreviated 4-year residence with Stobart, before the scandal, he would have begun to learn all aspects of watch- or clockmaking, including the use and maybe even the manufacture of a watchmaker's tools, the construction and fitting together of watch movements, and the technical illustration of the movement, showing the proportional sizes of the toothed wheels. This last element of the trade was particularly well suited to his artistic bent. He wrote in his journal that in his spare time he was ''Very much given to ye Amusement of Drawing, Planning of Maps and Buildings.''8 This was the germ of a lifelong passion for illustration that he would later apply to explaining astronomical concepts.9

Background: the age of Newton, Halley, and Cassini

We do not know what Munday taught Wright about astronomy and its affiliated field of mathematics, but he seems to have been well-supplied with books, which Wright eagerly borrowed. ''Mr. Munday reports I have stole all his Mathematicks from him,'' Wright observed in 1729.10

Munday introduced Wright to astronomy at a time of great renewal for all scientists or ''natural philosophers'' as they were then known. Some 40 years earlier, Isaac Newton had published his revolutionary treatise, Philosophiae naturalis principia mathematical, the ''mathematical principles of natural philosophy,'' better known by its abbreviated Latin title Principia. In this work he formulated the theory of gravitation as the force tending to attract massive objects toward one another, and he articulated the mathematical laws of motion that govern everything from the fall of an apple from a tree to the motion of a planet around the Sun. His theory explained such important phenomena as the Moon's orbit of the Earth and the establishment of ocean tides.

Mathematicians and astronomers, including Newton himself, immediately began applying the laws of motion and the theory of gravitation to elucidate the previously cryptic motions of solar system bodies such as comets, Jupiter's satellites, Earth's Moon, and the Earth itself, which shows small irregularities in its motion. Edmond Halley identified his famous recurring comet, for example, by applying Newton's laws. Halley gathered his predecessors' observations of the positions of comets and calculated the implied orbits, or paths, of these comets around the Sun, under the influence of gravity. Among the many curved paths he drew up, the orbits of comets seen in 1531, 1607, and 1683 struck him as very similar, and in 1705 he correctly inferred that a single comet had reappeared at intervals of about 76 years. His prediction of the next return of the comet would not be borne out until years after his death in 1742. When the comet appeared in December 1758, as he had foretold, the public acclaimed him anew as a great astronomer, but mathematicians had already recognized the success of his application of Newton's laws.

Wright began reading extensively in astronomy and mathematics just around the time of Newton's death in 1727 and the publication, in 1729, of an English translation of the Latin Principia. These events may have prompted Wright to read Newton's original works at that time, but whether he read Newton then or later, he almost certainly came across simplified explanations of Newton's concepts by authors such as William Whiston, a Cambridge professor and associate of Newton, and John Keill, a promoter of Newton's work at Oxford. Whiston was, to judge from Wright's quotations and borrowings, one of his favorite authors.

Wright would also have read of telescopic discoveries in the previous half-century, notably those of the Italian-French astronomer Gian-Domenico Cassini at the Paris Observatory. In the late 1600s Cassini captivated the public with large-scale maps of the Moon, showing its heavily cratered surface in unprecedented detail. He uncovered a new feature in Saturn's ring—a ring that Galileo had first seen only as a set of ear-like appendages on either side of the planet. Cassini saw and described a flat ring with a dark gap separating it into two parts, a gap still known as the Cassini division. Most importantly for the understanding of man's place in the cosmos, Cassini fixed the scale of the solar system itself, using the method of parallax (described in chapter 4). Although his results were subject to uncertainty, he established that the Sun lies on the order of 150 million kilometers (93 million miles) from the Earth.

Wright certainly was aware, too, of the circumstances that had led to the establishment of France's Observatoire de Paris in 1667 and England's Royal Observatory in 1675: the longitude problem. All too often, European ships carrying home the bounty from overseas colonies lost their way at sea or ran aground at night, for want of knowledge of their east-west position. (India's great non-telescopic observatories at Jaipur and elsewhere were completed in Wright's lifetime, but they were not dedicated to solving the longitude problem.)

Mariners, and mapmakers charting new territories in the Americas, desperately needed a way to keep track of time at sea. To calculate their longitude, they must compare their local time of day, as determined by the Sun, to Greenwich or Paris time, as determined by some kind of clock; the difference in time translated to a difference in longitude. Astronomers had vowed to decipher the complex motions of Earth's Moon and the motions of Jupiter's satellites so that these systems could be read as celestial ''clocks.'' Analysing these celestial timekeepers required new, more precise charts of the background stars, however, and so they petitioned their governments for telescopes and facilities.

John Harrison solved the longitude problem in the mid-1700s with a mechanical timepiece built to survive long sea voyages, and clocks eventually supplanted celestial means of marking Greenwich time aboard ship. But when Wright took up his mathematical and astronomical studies, the longitude problem still loomed in the astronomical community as the most pressing practical problem, and focused astronomers' attention on the accurate charting of the locations of the stars and the study of the planetary motions. Although it was surmised that the stars were distant suns, quite probably endowed with their own planetary systems, the stars themselves, the obvious differences among them in color and apparent size, and their tendency to form clusters did not elicit much interest.

Explorations

At 18, Wright was still far from making his mark on the world. Home again at Byer's Green, while his father and three justices of the peace negotiated a legal and financial termination to his apprenticeship, Wright dove back into his books.

A note in his journal from this period, when he was living with his parents and applying for work in nearby towns, shows that his interest in astronomy at this time had less to do with an ambition to observe or chart the stars and planets for himself than a desire to understand the Creator behind them. He wrote, ''Reflecting upon almost every object, conseive may find Ideas of ye Deaty and Creation.'' In this endeavor he was not alone, but following a certain vogue among churchmen of philosophical bent.11

When Newton formulated his laws of motion, he not only provided new tools for astronomers, but also spawned a new line of theological work. The great mathematician himself doubted that the universe's apparent stability could have arisen without God's design or intervention. The same gravitational attraction that gave rise to planetary orbits would cause the stars — indeed all matter—eventually to clump together. In the Principia, Newton suggested (rather unconvincingly, to the modern reader) that God prevented this catastrophe by removing the stars from each others' gravitational sphere of influence: ''[L]est the systems of the fixed stars should, by their gravity, fall on each other mutually, he hath placed those systems at immense distances one from another,'' he wrote. Elsewhere, he similarly suggested that the Creator would form and repeatedly re-form a system such as our solar system, to remove the irregularities of motion that would inevitably creep in as the planets and comets exerted gravitational effects on one another.12

Even those philosophers who would argue that God had designed a perfect, stable universe at the outset—and so had no need to intervene—liked to look for evidence of divine harmonies in the workings of nature. A number of books appeared on this astro-theological theme of searching for evidence of the Deity: in 1669, for example, John Craig published Mathematical Principles of Christian Theology, self-consciously modeled on Newton's Mathematical Principles of Natural Philosophy. Whiston, one of

Wright's favorite sources of quotations and inspiration, first brought out his influential work Astronomical Principles of Religion in 1717. William Derham enjoyed the success of his Astro-theology during Wright's youth.13 Wright shared the same impulse as these authors; a starting point for one of his proposed later tracts was, ''If you can not Believe in god and his infinite power which you do not see; you may still believe in his Nature and Wisdom which you do see.''14 The note in his journal about looking for signs of the Deity and Creation shows that his interest in astronomy was from the outset intertwined with his search for a moral principle in the universe.15

Wright's reading filled his time as he waited for responses to his queries about employment. Some two months after leaving Stobart, having failed to find any post despite widening his search to Newcastle and towns in Yorkshire, he gave up on business and took up the study of navigation. He resolved to be a ''saylor,'' and persuaded his father to support a trial voyage. In January 1730, he set sail for Amsterdam, full of hope for his new career.

Wright delighted in his view of the horizon at sea. With no mountains to clutter the view, and only monotonous gray swells in all directions, he must have found it easy to picture the Earth as a perfect globe. The trip broadened his horizons in a metaphorical sense, too. He took ''great Notice'' of Amsterdam's town hall or Stadhuis on Dam Square, and what he called its ''Geographical Pavement Figure.''16 It's not hard to imagine that this magnificent edifice, which locals nicknamed the eighth wonder of the world, inspired some of Wright's later efforts to design astronomically-themed buildings for the English aristocracy; the Stadhuis was everything Wright loved, and on a grand scale.

The citizens of Amsterdam completed their new town hall, then Europe's largest government building and a model of the new Classicist style, in 1665. The outer facade glorifies Amsterdam's trade with the four continents of Europe, Asia, Africa, and America, and features a large sculpture of Atlas carrying the world on his shoulders. Inside, the great Citizen's Hall is perfectly proportioned according to the classical Greek ideals revived and promoted by the architect Andrea Palladio. There, Wright admired the ''Pavement Figure'' — three circular maps in the marble floor, representing the eastern and western hemispheres and the stars of the northern hemisphere. (Paintings of the southern skies were added later. Halley had already charted some of the southern stars.) The corners of the hall bear depictions of Aristotle's four essential elements: earth, water, air, and fire. A guide to the building, now called the Royal Palace, sums up a description of the Citizen's Hall this way: ''The decorative scheme of the entire room is based on the universe, with Amsterdam at its center.''17

Wright probably would have enjoyed more travels abroad, but the life of a sailor didn't suit him. The sea disagreed with him, and he felt his duties were too dangerous. ''A very bad, tedious voage [voyage],'' he noted upon his return. ''Very near being cast away (by Canting ye Ballast) in a very great storm.''18 He returned to Sunderland and settled down—to the extent he was capable of settling—as a teacher of mathematics and navigation.

In winter there were plenty of seamen around to enroll for his classes because coal ships were laid up in port for the season, and Wright prospered. He suffered only a temporary setback in the summer of 1730; he had fallen in love with a ''Miss E. Ireland,'' but, although she agreed to marry him, he could not win her father's approbation in the face of ''two Rich Rivales.'' Wright bolted to London, ''[t]he disappointment not siting easy'' as he noted candidly.19 Just as he was about to board a ship bound for Barbados, a friend of his father somehow found him out and prevented his departure. Wright tarried in London for a while, working for makers of mathematical instruments, then accepted money from his father for the trip home and returned to teaching mathematics and navigation.

After the loss of ''E.,'' Wright appears to have made an effort not only to supplement his teaching income but to make a name for himself, at least locally. His efforts to create and distribute an almanac illustrate his tenacity and the supportive role of his family in this regard.

An annual almanac generally included the times of sunset and sunrise, a calendar of lunar phases, data on solar and lunar eclipses, and other information of interest to gentlemen-farmers or mariners. Some also included astrological prognostications. A well-known astronomical almanac, similar to the one Wright proposed, was available from Oxford, but Wright hit upon the idea of calculating his astronomical calendar to the longitude of

Durham, the nearest town to Byer's Green, and so tailoring it to the uses of his fellow north-countrymen.

Wright's calculations for 1732 were ready to be engraved and printed in the fall of 1731, but he had not allowed enough time for the printing and distribution. The Company of Stationers in London, the chartered organization that would have published the almanac, promised to do business with him the next year, if he could complete his manuscript earlier and come up with 500 subscribers. In 1732, he was ready in the spring with his calculations for 1733, and had found 900 subscribers. This time, however, the Stationers in London unexpectedly balked when he showed up in their offices, declining to compete with the venerable Oxford almanac. Wright demanded that they explain the situation in the Durham newspapers, to satisfy his subscribers there.

Wright was almost out of money when the Stationers turned him down, and he set out to cover the 200 miles home to Byer's Green on foot. Friends and relatives gave him shelter, food, and money along the way. ''Meet with uncommon Sevilities [civilities] upon ye Road,'' Wright noted in his journal.20

Wright was determined to revise his almanac and have it printed in Scotland. His long-suffering father, who had bailed him out so many times before, did not think this plan worth pursuing, but Wright set out on foot again ''with a small assistance from his [i.e., my] Mother and syster.'' Again his extraordinary luck on the road held out; he was accosted by two ''Highway Men,'' but they turned out to be of the most sympathetic sort. As Wright tells the story, they ''oblige him to sit down by them upon a green Hill, ask him many Question Relating to ye various states of Life, is satisfied with his Reasoning and answers, and makes no attempt to Rob him but directs him the Best Way.''21

In Edinburgh, Wright encountered yet another delay in publishing his almanac, and yet another promise to publish the next year's. In the meantime, he published ''with great Sucess'' a calculation of the upcoming total eclipse of the Moon, on November 20, 1732, and was ''very Fortunate in citing ye time.'' Unfortunately, the engraver and printer in Edinburgh proved to be ''a Rogue'' and took Wright's money without producing the second almanac, which Wright had re-calculated to the longitude of Edinburgh.22

By February 1733, a slightly older and much wiser Wright, back in England, had found employment as a companion to the Rector of Sunderland, and the tide of his affairs was beginning to turn. The commissioners of the river Wear, the port authorities, sponsored his invention of a ''composition'' or set of various types of sundials, and erected them on a pier in Sunderland. The local authorities paid for a printed description and explanation of them. And in the fall, at the age of 22, Wright finally achieved a kind of social and financial breakthrough: his employer Daniel Newcome, the Rector of Sunderland, introduced him to the Earl of Scarborough, who in turn invited him to London and became one of his patrons.

Early London years: astro-theological musings

Wright moved to London in the fall of 1733, and lived there for about 30 years before returning to the family estate at Byer's Green. It was in 1750 in London that he produced the innovative astro-theological and geometrical treatise for which he is now best known, An Original Theory or New Hypothesis of the Universe. According to the introductory pages to this work, he began constructing an astro-theological theory much earlier — in 1734, soon after moving to London, in fact—but for some reason he did not venture to publish his thoughts, eventually much revised in Original Theory, until he had seen several other, more purely astronomical, works in print.

During Wright's first year in London, 1733-1734, he appears to have been busy finding people who would pay in advance for, or subscribe to, a mathematical instrument he called the ''Pannau-ticon.'' No copy of the Pannauticon survives, so its function is unclear, but a notice on one of Wright's later works informs us that Wright had ''lately publish'd by Subscription the Perpetual Pannauticon or Universal Mariner's Magazine, being a Mathematical Instrument,'' and a different notice adds that the instrument explains ''the Lunar Theory and motion of the Tides.'' A printed key to the instrument mentions that it consists of a number of drawings or ''schemes'' showing ''divers Circles.''23

In promoting his Pannauticon, Wright had help from one of the first people he met in London, Roger Gale, who was to become a good friend. Gale was an antiquary who served as Treasurer of the Royal Society, an organization of natural philosophers chartered in 1662 to further the study of nature and to foster experimentation and mechanical or mathematical invention. Gale introduced Wright to the Royal Society, which allowed Wright to communicate his Pannauticon to that august body. From then on, Wright garnered subscribers left and right; the Earl of Scarborough even obtained permission for Wright to dedicate his instrument to the king, George II, and procured for him a subscription from the Prince of Wales.

Wright's sparse journal entries for the winter of 1733-34 indicate that his efforts to find subscribers kept him busy throughout the season. In the spring of 1734, he was occupied with preparing the copper plates of his Pannauticon schemes for the press, engraving himself those he could not afford to have engraved for him, and seeing the work through publication. Thus it was probably in the late summer of 1734 that he had time to think about his astro-theological view of the universe. After delivering copies of the Pannauticon to subscribers in London, he traveled north to the Sunderland and Durham area to visit his family and the Reverend Newcome, and to deliver copies of the Pannauticon to subscribers there. He returned to London in the fall.

Whether in London or in the north of England at the time inspiration struck, Wright found himself mulling over the possibility of a multitude of worlds. The theoretical existence of other inhabited planets, or even of solar systems around other stars, had been debated for centuries. Aristotle had scoffed at the idea of an infinite universe replete with other Earth-like planets, but his authority on the subject had been contravened by the Bishop of Paris in 1277, who ruled that to deny the possibility of an infinite universe, or of other creations, was to limit God's power. The idea of other worlds became even more attractive in the sixteenth century after Copernicus argued for a Sun-centered system of planets; indeed it was difficult to see the stars as other suns without contemplating also the likelihood of other planetary systems.

The problem for Wright was to locate Heaven and Hell in such a populated space. Some of the writers he admired proposed that Hell lay in the infernal center of the Sun, and the ''Throne of

God'' beyond the stars — in which case one might infer that each solar system had its own Hell, but shared the region of Heaven with other solar systems. Wright thought otherwise. The hypothesis he developed at this time presented a highly structured, symmetric universe centered on a ''Sacred Throne of Omnipotence'' and with room for ''myriads'' of planetary systems distributed around their respective suns.24

As was by now his habit, Wright created a drawing to explain the details of his hypothesis: for him, to think was to draw. Indeed, many of his publications were primarily artistic compositions, with the accompanying text, if any, playing the subordinate role of an explanation or key to the drawing. In the 1730s particularly, his aim seems to have been to provide a synoptic view of an entire field on very large pieces of paper. In 1731, for example, before he left the Sunderland area for London, he conceived ''a General Representation of Euclid's Elements in one Large Sheet: and the Doctrine of Plain and Spherical Trigonometry all at one View, on an other.'' In 1737, he was to create a work titled The Universal Vicissitude of Seasons, which he described as ''exhibiting by inspection at one view, the various rising and setting of the Sun to all parts of the World, with the hour and minute of day-break, length of day, night and twilight etc every day in the year.''25

To illustrate his hypothesis about the plurality of worlds, Wright created nothing less than a cross-sectional view of the entire universe. Unfortunately, the illustration is no longer extant. However, we can glimpse what he had in mind from two documents relating to the hypothesis, the latter possibly dating to 1738, and some undated sketches found among his papers. These two documents provide an important framework for understanding not only the 1730s hypothesis, but also the theory of the universe that was to follow in 1750. In both the earlier and later versions of his hypothesis, the Sun is embedded in a spherical shell of stars.

A sketch (figure 3.2), probably made later for the Original Theory, depicts two views of a universe similar to the one Wright conceived of in the 1730s. In the bottom view we see a small sphere at the very center, emblazoned with a triangular symbol similar to one Wright described in one document as a ''Hyroglyphic'' or ''Emblematic Trigon'' representing the divine

Figure 3.2 Two views of a "universe" of stars arranged in a spherical shell about a divine center. Undated sketch found among Wright's papers, probably made in preparation for his Original Theory of 1750. (Reproduced with permission from Hoskin (1971).)

presence.26 At some distance from this seat of God is a shell filled with stars, each apparently with its own planetary system shown by a set of circles. Dotted lines show the orbits of the stars, which are not confined to a plane as the planetary orbits are in his scheme, but circle the inner sphere in all directions, like strands of yarn in a knitting ball. The top view is a variant on the bottom one.

The first document describing the idea is a single paragraph, a brief description of his solution to the problem. The solution is

''represented in a section of ye Universe twelve feet radius, extending from the Imperial Seat or Sedes Beatorum to ye verge of chaos bordering upon ye infinite abiss.'' Surrounding the Sedes Beatorum, also called the Sacred Throne of Omnipotence, is a ''Region of Mortality'' in which planetary bodies such as the Earth, together with their suns, ''circumvolve'' around the divine center. Enclosing both these concentric spheres is dark space, ''supposd to be the Desolate Regions of ye Damnd.''27 As Wright makes clear, his ''section'' of the universe shows but a slice of the total, like the spoke of a wheel, with the central Sedes Beatorum on one side of the broadside and the dark and desolate regions at the other.

The second document, which reads like a lecture interpreting his mathematical and emblematical figures, seems to refer to at least two posters, or perhaps the 12-foot section drawing and an accompanying scheme.28 This text specifies that the Sun, along with the other stars, is in orbit about the Sedes Beatorum, and is to be found ''near ye center of ye middle region,'' i.e. near the middle of the spherical shell of Mortality enclosing the inner divine sphere. The stars filling the region of Mortality include those visible from Earth; Wright notes that the brightest, those of the first magnitude, are closest to our system and the rest ''proportionable removed'' according to their appearance. Those stars visible to the naked eye all lie within a circle of a certain radius around the Sun. Beyond them, Wright says, are the telescopic stars and beyond them more stars, ''by no means perceptible to ye human eye.''29 Thus the inhabitants of Earth are aware only of the nearest stars in the Region of Mortality, and cannot directly see even the bright glow of the divine center, or the dark empty spaces of the abyss.

This hypothesis made it possible for him to preserve a structure and spherical symmetry to the universe, and to account for a plurality of worlds—although not, strictly speaking, an infinite number, since the volume of space in the Region of Mortality is limited. In envisioning the stars as being in orbit around a divine center, and not static, his hypothesis also incorporated the recently discovered phenomenon of moving stars.

The stars had for centuries been viewed as fixed in place, forming an unchanging backdrop to the comings and goings of the Moon and planets. However, in 1717, Halley had discovered that some stars had moved since their positions were recorded by Hipparchus. Reviewing Hipparchus's data in Ptolemy's catalog, Halley found that the stars Aldebaran (then known as Palilicium), Sirius, and Arcturus had shifted their positions in ways that no other stars had, and the shifts could not be explained by any known instrumental or atmospheric factor.30 Perhaps, the feeling was, all the stars move, but long intervals of time were required to detect the movement, and only those stars nearest to us have a great enough displacement to be discerned over a span of several hundred years. For some astronomers and philosophers, including Wright, these motions explained the stability of the universe; the stars were not compelled to drift into one large agglomeration over time, under the influence of gravity, since they were constantly in motion and experiencing a continuously changing gravitational environment from the other stars.

However pleasing Wright found his vision of the grand plan of the universe, incorporating spherical symmetry, a plurality of worlds, and moving stars, he apparently kept it to himself or shared it only with friends for the time being. Perhaps his admiration for the Royal Society, and his desire to be taken seriously by its members, made him reticent on the subject of astro-theology. A draft of the Royal Society's statutes written in 1663 stated explicitly that its business was ''not meddling with Divinity, Metaphysics, Morals,'' or other unscientific fields such as poli-tics.31 Perhaps he simply lacked the nerve to assert himself as an authority in metaphysics. Whatever the reason, Wright's early drawings representing the moral and physical world together never circulated as a book. When he finally published a revised version of his theory in 1750, it was in part because he believed he had solved a very long-standing, purely astronomical problem: how to account for the appearance of the Milky Way.

Man of many talents

Life in London was good. Wright settled into lodgings in Piccadilly, the fashionable area near St. James' Palace, at that time the official royal residence. Having brought his Pannauticon project to a successful conclusion, he delved into the vibrant social and intellectual life of the city, giving a course of lectures in astronomy at Brett's coffeehouse in Charles Street near St. James's Square. Thinkers and businessmen liked to congregate in these types of establishments, which had been popular since the 1600s, to hold meetings, read a newspaper, or listen to a lecture. (Indeed, in later times, coffeehouses were sometimes known, somewhat pejoratively, as penny universities, because of the low cost of admittance.)

Wright readily made friends and found patrons, besides the Earl of Scarborough, in this new environment. The Earl of Pembroke became one of Wright's chief supporters, granting Wright the use of his library and nurturing his interest in architecture. John Senex, a well-known mapmaker who had published Halley's celestial and terrestrial maps and Whiston's astronomical diagrams, commissioned work from Wright and sent private students his way. The Duchess of Kent took Wright under her wing, ensuring that Wright moved in fashionable circles.

Gradually Wright evolved a routine of teaching private students mathematics or astronomy in winter and visiting aristocratic families, often at their country estates, for weeks at a time the rest of the year. He found himself in demand as a private tutor, mainly to ladies, for whom it was fashionable to study mathematical sciences and the use of globes. Thus he taught geometry to a Mrs. Townshend, the daughters of the Duke of Kent, and the daughters of Lord Cornwallis, and under his tutelage, the Duchess of Kent surveyed her garden and made a plan of it.

Wright evidently owned or had access to a number of scientific instruments, for he made astronomical observations and conducted several of his own surveys during his London years. His journal mentions no telescopes, but some of his works and magazine articles mention lens-based and mirror-based telescopes — a ''tube of two convex glasses'' in one instance, a ''five Foot Focus Reflector'' in another—most likely less than about 2.5 inches diameter aperture, affording a view of ninth or tenth magnitude stars.32 He used these telescopes to observe the stars, and also to study the appearance of comets. For surveying, he would have used a theodolite, a telescope equipped with a scale to measure precisely the horizontal or vertical angle between two observed objects.

Even before he left northern England, Wright had discovered that surveying could be a profitable sideline for someone with his knowledge of astronomy and mathematics. The owners of country mansions were just beginning to be swept up in the eighteenth-century English craze for ''naturalistic'' gardens enlivened with serpentine ponds, grottos, and artfully placed groves of trees; this was the era of gardening as landscape painting, with allusions to classical themes. On an occasional basis, Wright surveyed and made maps of the country estates of his friends and patrons, laying the basis for their landscaping plans. This type of mapmaking exercise no doubt contributed to Wright's unique combination of interests and spatial skills that meant he was one of the first to consider the effect of geometrical perspective on our perception of the universe of stars.

The technique of triangulation, obtaining the distance of a marker by observing it from two different positions, is at the heart of surveying. A surveyor first lays out a baseline, a straight line of known length (see figure 3.3). He views the object whose distance is to be determined from the two ends of the baseline in turn. A distant object forms the apex of a long triangle, while a nearby object forms the apex of a short, squat triangle. The known length of the baseline, and the measured angles between the baseline and the lines of sight to the marker, pinpoint the location of the marker. As Wright roamed the gardens he surveyed, mapping the locations of trees and ponds and considering the views from different angles, he developed the art of mentally relating three-dimensional landscapes to two-dimensional maps—an art that would later inform his efforts to understand the structure of the Galaxy.

Teaching, visiting friends and patrons, and surveying estates kept Wright pleasantly occupied and intellectually stimulated. Particularly during his first few years in London, he seems to have experienced a surge in creativity. He devoted his spare time to his old passion of astronomical and architectural drawing. Some of his projects existed only in design, on copper plates and prints, and some he executed. One of his largest sculptural works was undoubtedly his model of the solar system, a ''system of ye Planetary Bodies in true Proportion Equal to a Radius of 190 feet. (all Brass),'' which he presented to the Earl of Pembroke. He designed a ''Hemesphereum,'' probably a domed ceiling with astronomical embellishments, and drew plans for different kinds of sundials. He devised something he called an

Figure 3.3 Technique of triangulation. A surveyor lays out a baseline AB of known length. From each end of the baseline, the angles to the object at C are measured. (If the length of the baseline AB is known, and the angles CAB and CBA are known, the distance AC or BC can be found from geometry, without actually pacing it out.) (Credit: Layne Lundstrom.)

Figure 3.3 Technique of triangulation. A surveyor lays out a baseline AB of known length. From each end of the baseline, the angles to the object at C are measured. (If the length of the baseline AB is known, and the angles CAB and CBA are known, the distance AC or BC can be found from geometry, without actually pacing it out.) (Credit: Layne Lundstrom.)

''Astronomical Fan.'' In 1737 his journal records, ''His invention at this time run to(o) fast for Execution.''33

Wright's mother died in 1741 and his father in 1742, so he could no longer turn to them for support. But by this time he was well established in London, and had found his niche in society.

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