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According to his own account, Robert Hooke was born at exactly noon on 18 July 1635, at Freshwater on the Isle of Wight. What we know of his early life comes from two sources. John Aubrey’s Brief Lives is always entertaining, although not always accurate, but Aubrey was a friend of Hooke and had many conversations with him. Another friend, the naturalist Richard Waller, knew Hooke in later life, and was responsible for publishing the Posthumous Works of Robert Hooke in 1705, putting into print some of Hooke’s previously unpublished lectures. Waller’s introduction to that book drew, he tells us, on an autobiographical memoir that Hooke started to write but never finished, and which is now lost. The story pieced together from these two sources can be fleshed out, however, with other information about events on the Isle of Wight in particular, and across Britain in general, at the time Hooke was growing up. It was certainly an interesting time to be alive, taking in civil war and the execution of a king before the boy was fourteen.

Hooke’s father, John, was the curate of All Saints Church, where the rector was Cardell Goodman, a staunch Royalist and former member of Westminster School and Christ Church, Oxford – connections that would in due course become important to Robert. His mother, Cecellie, was the second wife of John Hooke, presumably a good deal younger than him, and Robert was by some way the youngest of four children. He had two sisters, the younger of whom was seven years older than him, and a brother, John junior, born in 1630.

Robert was a sickly baby who was christened the day after his birth, probably because he was not expected to live, but he survived to become a sickly child. He was too delicate to be sent away to school in Newport like his brother but was educated at home by his father. Although plagued by recurrent headaches and other ailments, this left him plenty of time to wander the south-west corner of the island, gradually becoming stronger, and to follow his own interests, which leaned towards practical activities such as making working models. These demonstrated a rare skill at an early age. He built a model ship, described by Waller as ‘about Yard long, fitly shaping it, adding its Rigging of Ropes, Pullies, Masts, &c. with a contrivance to make it fire off some small Guns, as it was sailing cross a Haven of pretty breadth’ (probably Yarmouth). When he saw a brass clock that had been taken to pieces for repairs, he copied the components in wood and put them together to make a clock, which worked tolerably well. The downside of all the hours he spent over a workbench was that by the time he was sixteen Robert had, he told Waller, developed a pronounced stoop, sometimes referred to by his biographers as a hunchback. As these examples show, Robert Hooke was a precocious ‘mechanic’ of rare skill. But his skills extended beyond the practical. When the artist John Hoskins, a painter at the court of Charles I, visited the island, Robert watched him at work, then made his own paints from materials to hand, such as coal, chalk and an iron ore known as ruddle, and used them to copy paintings hanging in the house, to such good effect that Hoskins suggested he could have a career as an artist.

The other formative influence on the young Hooke was the world around him. That part of the Isle of Wight offers spectacular scenery, chalk cliffs, and the dramatic sight of the Needles, a series of chalk spires rising from the sea at the end of a chalky spine running across the island. Many of the island strata are rich in fossils. Even as a child, Robert was intrigued by the discovery of the shells of sea creatures at the top of these cliffs, a long way above the waves. Most people in those days, if they thought about such things at all, assumed that this must be something to do with the biblical flood. But even though he was the son of a curate, Hooke had doubts, which developed over the years into ideas that culminated in a series of lectures at Gresham College, published posthumously as A Discourse on Earthquakes. Way ahead of his time, as we shall see, Hooke realised that the landscape we see around us today is a result of geological processes operating over immense spans of time, far longer than the then popular biblical timescale of Bishop James Ussher. Much later, he recalled how as a child he had observed a cliff made of layers of material, one of which, far above he sea, was a band of sand ‘filled with a great variety of Shells, such as Oysters, Limpits, and several sorts of Periwinkles.’^fn1

These activities took place against the background of the Civil War (actually a series of wars), which lasted from 1642 to 1651. Although the Isle of Wight was staunchly Royalist, its geographical isolation just off the south coast of England, and a judicious surrender to Parliament at the beginning of the conflict, spared it from the turmoil suffered by much of the country, but it was a natural place for Charles I to set up a Royalist base when he escaped from Parliamentary captivity in November 1647 (it is widely thought that he was allowed to escape by the Parliamentarians, at a loss to know what to do with him, in the hope that he would flee to permanent exile in France). This adventure came to nothing, but must have made an impression on Robert, who remained a Royalist throughout his life.

All the model-making and wandering abroad in the countryside came to an end, however, in October 1648, when Hooke’s father died. Robert was just thirteen. John had been ill for some time, and knowing that his time was short had made careful provisions for the family. He left the boy as his share ‘forty pounds of lawful English money, the great and best-joined chest, and all my books’; there was an additional legacy of £10, which had been held by John in trust for Robert, from the will of Robert’s maternal grandmother. The total sum of £50 sounds modest today, and some accounts describe the boy as an impoverished orphan. But in terms of spending power, it was equivalent to about £20,000 today, certainly enough to give him a start in life, even if he would soon have to find a way to earn a living. It may be significant that Robert’s inheritance was entirely portable – as Lisa Jardine put it: ‘cash, books and a chest to carry them in’. Clearly Robert’s future away from the island was already planned. The first step down the road to that future took him as an apprentice to the studio of the portrait painter Peter Lely at Covent Garden in London,^fn2 just about at the time the King’s adventure on the island came to an end and he was carried off once again, this time permanently, by the forces of Parliament. Charles was beheaded on 30 January 1649.

Hooke was almost certainly introduced to Lely by John Hoskins, who may have been the person who took him from the Isle of Wight to London. It is easy to imagine the likely fate today of a thirteen-year-old boy with £20,000 in his pocket, installed as an apprentice to an artist in Covent Garden, part of the expanding metropolis of London, then home to some four hundred thousand people. But children were expected to grow up more quickly in the seventeenth century, and Hooke, as he soon demonstrated, was no ordinary child, even by the standards of his day.

But Robert did not stay with Lely for long. Almost as soon as he was installed in Lely’s studio, Robert had second thoughts. According to John Aubrey, who later became a close friend of Hooke, he decided that Lely had nothing to teach him: he ‘quickly perceived what was to be donne, so, thought he, why cannot I doe this by my selfe and keep my hundred pounds?’^fn3 According to Waller, Hooke was put off a career as an artist by the smell of the painting materials, which brought on a recurrence of the headaches that had plagued his childhood. Both accounts may, of course, contain part of the truth. And in the light of what happened next, there may be a third thread to the story.

After a brief time with Lely, Hooke enrolled at the prestigious Westminster School, where the headmaster, Richard Busby, held on to his post in spite of his Royalist sympathies and the proximity of Parliament. It is easy to identify the connection that took him there. Cardell Goodman, the rector at Freshwater, had been a pupil at the school, and was a witness to and executor of the will of John Hooke. Our own speculation is that Robert was supposed to be going to Westminster School all along, with his money and chest full of books, but was briefly tempted by the thought of becoming an artist. It is fortunate for the development of science in Britain that he quickly came to his senses and followed what was probably his father’s plan.

Busby was an enlightened headmaster (in some ways; he was also a strict disciplinarian) who charged pupils according to their intellectual ability as well as their ability to pay. Some paid as much as £30 a year, which would soon have eaten up Robert’s inheritance. But some paid nothing at all, and were lodged in Busby’s house. There is no record of what, if anything, Robert paid for his education, but he was one of Busby’s special cases, bright but relatively poor boys who did not necessarily follow the regular curriculum (which still concentrated on the Classics, Greek and Latin literature) but had freedom to develop other skills that might be useful in later life. The ‘regular’ pupils, sons of gentlemen all, and including John Locke, Christopher Wren (three years Hooke’s senior, who became his close friend in Oxford) and John Dryden, had no need to get their hands dirty in this way. But it suited Hooke perfectly.

Although he was not often seen at lessons (at least, according to Aubrey), during his time at Westminster Hooke mastered Latin and could converse in the language, and studied Greek and Hebrew, like the classical scholars. He also, though, learned to play the organ, a skill that would soon come in handy, and mastered the mathematical works of Euclid. According to Waller:

he fell seriously upon the study of the Mathematicks, the Dr. [Busby] encouraging him therein. and allowing him particular time for that purpose. In this he took the most regular Method, and first made himself Master of Euclid’s Elements, and thence proceeded orderly from that sure Basis to the other parts of the Mathematicks, and thereafter to the application thereof to Mechanicks, his first and last Mistress.

Instead of his lessons, he could be found in one of the workshops associated with the school, where he spent the long hours bent over a lathe that he thought produced his stoop. It seems more likely, however, that he suffered from a condition known as Scheuermann’s kyphosis, a curvature of the spine that develops in adolescence and may have a genetic basis but has been linked to poor diet when young.

Hooke’s interest in ‘Mechanicks’ while at Westminster led him, among other things, to devise ‘thirty severall wayes of Flying’, he later told Aubrey. John Wilkins, the Warden of Wadham College in Oxford, was another person interested in mechanical devices, and had written a book about them, published in 1648, with the splendid title Mathematicall Magick, or the wonders that can be performed by mechanical geometry. The book dealt with the use of levers, pulleys and other mechanical aids for practical uses, then went on to more speculative discussion of mechanical automata, including flying machines (ten years earlier, Wilkins had speculated in print about the possibility of flying to the Moon). It seems that Hooke’s interest in mechanical devices, and in particular flying machines, was reported to Wilkins by Busby, helping to smooth Hooke’s path when in due course he too moved on from Westminster to Christ Church. Indeed, Wilkins gave a copy of his book to the boy while he was still at Westminster and Hooke still had the book at the time of his death. When he made the move to Oxford, he left behind someone who had become a firm friend, not just his schoolmaster. Busby and Hooke remained friends for the rest of Busby’s life (he died in 1695), and Hooke was the architect for a church and vicarage built for Busby at Willen, in Buckinghamshire, in the 1680s. When Busby was Archdeacon of Westminster, Hooke carried out several commissions at the Abbey, including repaving the choir, where the black and white marble flooring he had installed can still be seen. But an architectural career lay far in the future when Hooke went up to Oxford in 1653, at the age of eighteen.

The path from Westminster to Christ Church was a well-trodden one. Each year, four Westminster students were awarded scholarships to the college; but Hooke was not one of the four selected in 1653. Instead, he was awarded a choral scholarship, thanks to his musical ability. This seems to have been literally money for nothing, because during the Parliamentary Interregnum such frivolities as church music were banned. In addition, we are told that Hooke acted as a servitor (or ‘subsizar’) to a ‘Mr Goodman’. The position of servitor, acting as a servant to a more wealthy student, was a way for less well off but academically gifted students to make their way at Oxford or Cambridge in those days. The duties might be very light or more onerous, depending on who was being ‘served’. But there is no record of a student called Goodman in Christ Church at the time Hooke was up in Oxford. The logical conclusion is that he was being supported by Cardell Goodman, himself a former Westminster scholar and Christ Church graduate, perhaps with the notional title of servitor for administrative reasons. Although Goodman died in 1653, he could well have left money for the purpose. If so, once again it was money for nothing, and a clear indication of the high academic reputation Hooke had already achieved at the age of eighteen.

Hooke’s time as a student in Oxford was distinctly out of the usual path of other students. Although he went up to Christ Church in 1653, he did not matriculate (in effect, register to study for a degree) until 1658, and he never took the BA examination, although he was awarded an MA in any case in 1663, after he had left Oxford (this is not, as we shall see, totally unlike what later happened to Edmond Halley). Instead of following a conventional course of study, alongside what (if anything) he was studying in college he worked as an assistant to two of the pioneering scientists of the time, first Thomas Willis and then Robert Boyle.^fn4 The connection with Willis, and through him a group of scientists, had begun by 1655, when Hooke was twenty.

At the time, a new way of investigating the world was being pioneered, and its key feature was experiment. Since the time of the Ancient Greeks, philosophers had developed their ideas by logic and reason, without actually getting their hands dirty by carrying out experiments. This led to the wide dissemination of such ideas as the notion that a heavy object falls more quickly than a light object, even though a simple experiment was sufficient to prove the idea wrong. By the early seventeenth century, individual scientists were applying the experimental method – Galileo most famously, who, although he never did drop objects from the tower in Pisa, did do experiments rolling balls down inclined slopes to see what really happened to them. In England, William Gilbert, a physician at the court of Queen Elizabeth, carried out many experiments with magnets and made huge advances in understanding the nature of magnetism, but equally significantly he explained the importance of the scientific method of testing ideas by experiment. Indeed, his writing directly influenced Galileo, who read Gilbert’s book De Magnete. Another pioneer of the experimental method was William Harvey, who discovered the circulation of the blood. Harvey had an Oxford connection – as one of the King’s physicians he had been residing in the city with Charles when the King made it his capital during the Civil War. Ironically, though, the person who had the most direct influence on the new experimenters was not an experimenter himself. Francis Bacon, one of the key politicians of the Elizabethan age, published his ideas about the experimental method of scientific research in 1620, under the title Novum Organum. In essence, Bacon’s argument was that progress should be made by collecting facts, forming hypotheses based on study of these facts, then (crucially) using these hypotheses to make predictions that could be tested by carrying out experiments. As long as the experiments agreed with the predictions, the hypothesis being tested could be elevated to the status of a theory, but any theory could potentially be brought crashing down by a single experiment that gave results that did not match its predictions. In due course, the founders of the Royal Society, led by the same John Wilkins we have already met, would explicitly found their institution on their interpretation of Baconian philosophy. And some of those founders were experimenting in Oxford in the 1650s.

The first stirrings of the scientific debates that led to the founding of the Royal Society took place in London, in the mid-1640s, where a group of men, including Wilkins, used to meet to discuss ‘experimental philosophy’. This was at the height of the political and religious turmoil of the Civil Wars, and these gentlemen consciously made a decision not to discuss those contentious topics, but to stick with what we now call science – which must have been something of a relief to them from the uncertainties of everyday life. But at that time the group was essentially a talking shop, not a centre for experiments. After the success of the Parliamentary forces, the former Royalist stronghold of Oxford was reorganised, with many people regarded as King’s men ejected from their posts and being replaced. This took several of the London group to Oxford, where Wilkins became Warden of Wadham College in 1648, and a member of the triumvirate overseeing the University on behalf of Oliver Cromwell in 1652. In 1656, Wilkins married Cromwell’s widowed sister, Robina, who was a couple of decades older than him, cementing his position in the establishment. By then, Cromwell was the Lord Protector, and gave Wilkins a special dispensation to marry even though his post as Warden officially required him to remain celibate. This seems not to have been pure self-interest on Wilkins’ part, because John Evelyn, who knew Wilkins well, tells us that he was:

A most obliging person, [who] had married the Protector’s sister, to preserve the Universities from the ignorant Sacrilegious Commander and soldiers, who would fain have been demolishing all bothe [Oxford and Cambridge] and persons that pretended to learning.

By the time Hooke came to Oxford, the group of experimental philosophers was already holding regular meetings (sometimes referred to as a ‘philosophical club’) at Wilkins’ rooms in Wadham. It was at this time that they began to put the ‘experiment’ into experimental philosophy. Hooke was, of course, already known to Wilkins through Busby, and Thomas Willis was another member of the ‘club’, which was some thirty strong. Willis was a physician and chemist who was particularly interested in the workings of the brain. He was also a member of another ‘club’ – the Westminster/Christ Church old-boy network (indeed, he had been a contemporary of Busby at Christ Church as an undergraduate). So it is no surprise that Hooke became an assistant to Willis, living in his house, Beam Hall, opposite Merton College Chapel, and preparing the medicines for Willis’ patients, as well as helping out with chemical experiments. It was from Willis, too, that Hooke learned dissection.

If this meant that Hooke was neglecting his formal studies, it certainly did him no harm. And he was certainly more interested in learning, by whatever means, than many of the ‘young gentlemen’ who regarded their time at university as something of a holiday. Even at the height of the Puritan regime, with daily prayers at 5 a.m. and 5 p.m., services on Thursdays and Sundays and other devotions, it was necessary for the authorities to instruct the Dean of Christ Church to ‘take special care to reform all scandalous fashions of long and powdered hair, and habits contrary to the status of the University and that decency and modesty which is necessary for young students’, followed by a demand ‘to punish the abuse of swearing’. In 1653, the year Hooke went up, another edict took steps ‘for the repressing the immoderate expenses of youth in the College, that no gentleman commoner shall battel in the buttery above 5 shillings weekly’. Not that these financial restrictions would have meant much to the impoverished Hooke.

There was, however, one new temptation that Hooke fell for, and consumed eagerly throughout his life. The first record of coffee being brewed in England comes from the diary of John Evelyn, who wrote on 10 May 1637 ‘There came in my time to the College [Balliol] one Nathaniel, out of Greece … He was the first I ever saw drink coffee.’ Nathaniel was later sent down (expelled), we don’t know why, but went on to become Bishop of Smyrna, so whatever misdemeanour it was didn’t harm his career. Perhaps partly thanks to his example, in 1651 the first coffee house in England was opened on the site of what is now The Grand Café, on the High Street. Its proprietor was a man called Jacob, from the Lebanon; the first coffee shop in London was opened the following year, by Pasqua Rosee, from Turkey, in St Michael’s Alley, off Cornhill. By the end of the 1650s, there were more than eighty coffee houses in the City of London. Apart from Hooke’s personal addiction to coffee (which may help to explain both the long hours he worked and some of his later ailments), this was an important event for science, as well as society at large, because coffee houses became the preferred meeting places of natural philosophers such as Hooke, Halley and their friend Christopher Wren. A coffee house even comes into the story of the discovery of the inverse square law of gravity.

Although ‘only’ Willis’ assistant, Hooke attended meetings of the philosophical club, and absorbed knowledge from its other members, notably Seth Ward, the Savilian Professor of Astronomy; at Ward’s request, Hooke devised a mechanism to improve the regularity of a pendulum clock for astronomical timekeeping, and this led to a lifelong interest in clocks and the problem of finding longitude at sea. It was also here that he met Wren, and during his time in Oxford he continued his interest in flying. But the single most important thing that happened to Hooke in Oxford was that Wilkins introduced him to Robert Boyle, with the recommendation, which Boyle accepted, that Hooke should become Boyle’s assistant.

Boyle had reached Oxford by a circuitous route. Many accounts simply describe him as a rich aristocrat who had the time and money to indulge his interest in experimental philosophy. But things were never that simple in the England (and, especially in Boyle’s case, Ireland) of the middle decades of the seventeenth century. Boyle’s father, Richard Boyle, was indeed the Earl of Cork and filthy rich, but he was not the latest member of a long aristocratic line. Richard Boyle was what might now be called an entrepreneur, in the pejorative sense of the term. Born in England in 1566, into a respectable but unremarkable family, he became a penniless orphan before he was twenty and went to Ireland (then an English colony) to make his fortune. With the aid of marriages to a wealthy widow, and after she died to the daughter of the Secretary of State for Ireland, and financial dealings that were often on the shady side of legality, he succeeded in his aim so well that he became possibly the richest man in either Ireland or England, able to buy his title and the respectability that went with it.

Wheeling and dealing didn’t take up all of Richard Boyle’s time. Along the way he fathered seven daughters and six sons, before the late addition of Robert, on 25 January 1627, when Richard Boyle was sixty and his wife Margaret forty years old. Yet another daughter was born three years later, but complications associated with the birth killed Margaret. The last girl was named after her.

With no mother from the age of three, and far down the pecking order for any inheritance of either titles or money, the Honourable Robert Boyle (to give him the only title due to him) was initially brought up and educated at home, in the care of family retainers, but later went to Eton. There he was recognised as an outstanding scholar at a very young age, and first encountered the books of Nicolaus Copernicus and William Gilbert. But at the age of twelve, in 1639, Robert was plucked out of school and sent with his brother Francis, then fifteen, on the Grand Tour of Europe that was de rigueur for the sons of wealthy gentlemen. Their education was not forgotten. They were accompanied by a tutor, and visited many seats of learning – they were in Florence in 1642 when Galileo died. But when they were about to return home, rebellion broke out in Ireland. This was one of the early precursors to the Civil Wars, and although Francis was considered old enough to be summoned home to help suppress the rebellion, Robert was told to keep away until the fighting was over. The rebels, however, were not suppressed without serious consequences for the Boyle family. Two of Robert’s brothers (not Francis) were killed, and the grand old Earl of Cork lost most of his money and land. He died in 1643, soon after this phase of fighting finished. So when Robert returned to England in 1644, he had no money and had not been educated for any kind of useful career. Worse, by then the ‘proper’ Civil War was raging. He was saved by his sister Katherine, thirteen years older than Robert, who had married to become Viscountess Ranelagh, and lived in London but apart from her husband.

At first, Robert lived in Katherine’s house. She was a known Parliamentarian sympathiser with many powerful friends in London, which was controlled by Parliament. Robert judiciously never gave any indication of preferring one side or the other in the Civil Wars, probably because he genuinely just wanted to be left alone to get on with his life in peace. Katherine helped him to find a retreat from the turmoil of the times. Their father had left to Robert a small estate in Dorset – not much compared with the large estates in Ireland once intended for the older brothers, but enough for the youngest son, and by chance one of the few possessions the Earl had left at his death. Thanks to Katherine’s connections, the estate was not confiscated by Parliament, and Robert was allowed to live there from 1645 onwards, setting up his own laboratory where he carried out chemical experiments. On visits to London, he stayed with Lady Ranelagh, and like-minded experimental philosophers used to gather to meet with him at her house. Boyle referred to this as an ‘invisible college’; we don’t know who was involved, but there must have been considerable overlap with the group we mentioned earlier, including Wilkins.

Boyle’s fortunes improved in the 1650s, after the Civil Wars ended. One of his surviving brothers, now Lord Broghill, was in favour with Parliament for his part in crushing the Irish. This rubbed off on the rest of the Boyle family, and Robert was able to visit Ireland to pick up some of the threads of their former life. Horrified by the terrible conditions of the Irish people, after some soul-searching he got the estates running as a benevolent landlord (by the standards of the time) who used much of the income for charitable ends. This still left him enough to live on comfortably and continue in the role of gentleman scientist back in Dorset. But John Wilkins, who had met Boyle in London and knew his abilities, invited Robert to move to Oxford, where he could not just carry out his own experiments but be in the company of other people with similar interests. After mulling the offer over, Boyle made the move in 1655. He was never formally part of the university (as he put it himself, ‘never a Professor of Philosophy, nor a Gown-man’), but he had his own laboratory, and he also (as Wilkins had probably hoped) helped to finance the work of some of his fellow experimental philosophers. Boyle lived and worked in a house known as Deep Hall, on the High (convenient for the coffee shops!), and it was here, in 1656 (the year, incidentally, that Edmond Halley was born), that Robert Hooke came to live and work as Boyle’s paid assistant, although possibly they had already met.

Back in September 1653, when Wilkins was already trying to persuade Boyle to move to Oxford, he had sent a letter to him by messenger. It read, in part:

This bearer is the young man I recommended to you. I am apt to believe, that upon trial you will approve of him. But if it should happen otherwise, it is my desire he be returned, it not being so much to prefer him, as to serve you.^fn5

Lisa Jardine has suggested that the young man in question was Hooke, and that he was sent as part of the attempt to entice Boyle to Oxford, by showing that a skilled assistant would be available there:

If it be not, Sir, prejudicial to your other affairs, I should exceedingly rejoice in your being stayed in England this winter, and the advantage of your conversation at Oxford, where you will be a means to quicken and direct us in our enquiries … shall be most ready to provide the best accommodation for you, that this place will afford.

The immediate plan to persuade Boyle to Oxford that winter was aborted because he had to travel to Ireland to deal with the urgent business concerning the family estates we have already mentioned. The young man, presumed to be Hooke, returned to Oxford. But when Boyle did make the move some two years later, it seems that he was already aware of the abilities of the man who did indeed become his assistant.

The greatest achievement of the Boyle–Hooke collaboration was an improved air pump, which made it possible for them to carry out experiments both at greatly reduced air pressure and at pressures greater than ordinary atmospheric pressure. That simple sentence, though, needs unpacking in order to put Hooke’s achievements, in particular, into perspective.

First, although Hooke was a paid assistant to Boyle, this was a genuine collaboration. Hooke was more than a ‘mere’ technician who did things at Boyle’s direction. This was a very unusual – indeed, possibly unique – working relationship for the time, but it is made clear in Boyle’s published works, where Hooke is regularly mentioned by name as a co-experimenter. Other assistants are not so acknowledged. Secondly, an air pump might not sound like a dramatic invention today. But in the middle of the seventeenth century it was the highest of high-tech scientific equipment, equivalent, in terms of the insights it gave, to CERN’s Large Hadron Collider, or the Hubble Space Telescope, today. It was cutting-edge technology, leading to breakthrough science. And the man who made the air pump, and made it work, was Robert Hooke, still in his early twenties. If there had been Nobel Prizes in the seventeenth century, Hooke would have walked away with one, for this achievement alone.

It all started with an experiment carried out by the Italian Evangelista Torricelli (one of Galileo’s pupils) in 1644. This seemed to shed light on a puzzle that had vexed philosophers for centuries: was it possible for a vacuum, nothing at all, to exist? One school of thought held that matter must be continuous; a rival hypothesis described matter in terms of tiny particles (atoms) moving through the void (vacuum, or empty space). Torricelli took a glass tube, closed at one end, and filled it with mercury. He then put a finger over the open end, and submerged that end below the surface of a dish of mercury before taking his finger away and raising the closed end of the tube into the vertical. Instead of all the mercury flowing out of the tube, the level dropped only until there was a column nearly thirty inches high standing above the level of the liquid in the dish, with nothing at all in the space above the column. This seemed to be the definitive proof of the reality of the vacuum, and along the way the height of the mercury in the tube was explained as a result of the pressure of the weight of the air pushing down on the surface of the mercury in the dish. Torricelli had invented the barometer, for measuring atmospheric pressure, and similar instruments were soon tested by being carried up mountains, where the lower air pressure meant that the column of mercury was shorter than at sea level. Which suggested that if the air continued to thin out, then above the atmosphere there must be empty space.

Instead of carrying the equipment up a mountain, Boyle wanted to try it out inside a vessel where air could be pumped out to lower the pressure. If he could make a vacuum inside the vessel, the level of mercury in the column would fall as the air was removed, until it would not be supported in a column at all. But first, he needed a way to make a vacuum in the laboratory. This is where Hooke came in. Otto von Guericke, in Saxony, had already made a reasonably efficient air pump, which he had used to suck air out of two large copper hemispheres that were placed together rim to rim to make a sphere, but with no mechanical fastenings at the join. With air pressure inside the sphere reduced, the pressure of the atmosphere outside squeezed the hemispheres together so tightly that in a famous demonstration made to Emperor Ferdinand III in 1654 thirty horses could not pull them apart.

Von Guericke’s pump was large and cumbersome, needing two men to operate, and, of course, there was no way to see inside his copper sphere. Boyle needed something that could be operated by one man, with a chamber made of glass through which experiments could be observed. He first approached the greatest scientific instrument maker of the time, Ralph Greatorex, in London. But his forte was making precision instruments, and his attempt at the heavier machinery required for the pump was not up to Boyle’s needs. So it was Hooke, at the end of the 1650s, who designed and built the breakthrough instrument, using funds supplied by Boyle. He went to London to oversee the manufacture of the heavy components in the workshops there (we don’t know if he worked on these himself), then had them taken to Oxford, where he put the pump together and made it work.

The vacuum chamber consisted of a glass sphere fifteen inches in diameter, known as the ‘receiver’, with a brass lid four inches in diameter, which could be opened to place apparatus inside the sphere. A tapering hole in the base of the sphere stood on top of a tight-fitting brass cylinder, sealed with a leather collar. The brass lid had a small tight-fitting stopper, sealed with oil (referred to by Hooke as ‘sallad oil’), that could be turned to tug a string attached to the stopper in order to set off an experiment inside the globe. The cylinder below the globe connected to a brass pump fitted with an ingenious rack-and-pinion system, which allowed air easily to be pumped out of or into the globe. Hooke’s pump sucked air from the cylinder using a piston that was connected to a rod cut with teeth which engaged with a gear wheel that could be wound with a handle to push the piston up, forcing air out through a one-way valve, then pull the piston down, leaving a vacuum in the tube. The piston could be pumped up and down repeatedly, sucking more and more air out of the glass vessel. This apparatus became known as ‘Boyle’s air pump’, which it was in the sense that he paid for it and owned it (just as Dolly Parton’s hair is her own). But as Boyle acknowledged, it was made by Hooke, and Hooke was the experimenter who operated it during the many investigations that followed. In the fragment of autobiography quoted by Waller, Hooke said:

In 1658, or 9, I contriv’d and perfected the Air-pump for Mr Boyle, having first seen a Contrivance for that purpose made for the same honourable Person by Mr Gratorix, which was too gross to perform any great matter.

Some idea of the significance of the pump is that, even by the end of the 1660s, there were only half a dozen comparable air pumps in Europe, and three of them had been made by Hooke.

Boyle and Hooke carried out many experiments with their pump and vacuum chamber – Boyle later described forty-three of them in his book New Experiments Physico-Mechanical Touching the Spring of the Air, published in 1660. These included burning (or attempting to burn) substances such as candles, coal, charcoal and gunpowder in a vacuum, with results that convinced them that fire was not one of the ‘four elements’ (fire, earth, air and water) as the Ancient Greeks had taught, but involved a chemical process. Candles, for example, went out when air was removed from the globe, and burning coals died away, but, crucially, reignited when air was let back in. One of the other experiments showed that water boils at a lower temperature when the air pressure is reduced. But one of their most important discoveries is hinted at in the title of Boyle’s book. Every stroke of the handle of Hooke’s air pump demonstrated the ‘spring’ of the air, just like the springiness felt when using a bicycle pump today, and Hooke set out to measure this springiness – what we now call air pressure.

Around this time, at the end of the 1650s, the Englishman Richard Towneley was carrying out experiments with a Torricelli barometer on Pendle Hill, in Lancashire. He was following the example of continental experimenters, notably Florin Périer. Like them, he found that the pressure of the air measured by the barometer is lower at higher altitude, and he surmised (without carrying out experiments to test the idea) that the pressure is less because the air is thinner – that is, less dense – at higher altitude. He mentioned this idea to Boyle, who asked Hooke to devise a way to test it.

Hooke did this in 1660 or 1661, using a long glass tube shaped like the letter J, with the top open and the short arm of the J at the bottom sealed. He poured a little mercury into the top of the tube so that it partly filled the U-bend at the bottom but left some air trapped in the closed end. With the level of mercury the same on both sides of the U-bend, the trapped air was at atmospheric pressure. But Hooke could increase the pressure on the trapped air by pouring more mercury in, forcing some of it round the bend and squeezing the trapped air into a smaller volume. Boyle was short-sighted and bad at arithmetic, so we know for sure that it was Hooke who not only designed the experiment but also made the careful observations and records that showed that the volume of the trapped air was inversely proportional to the pressure applied. Double the pressure, and the volume halves; triple the pressure and the volume is reduced to one-third, and so on. These results were published in the second edition of Boyle’s book, in 1662, and became known as ‘Boyle’s Law’, although he did not use that name himself. Hooke’s own account appeared in his book Micrographia, published in 1665:

Having lately heard of Mr. Townly’s Hypothesis, I shaped my course in such sort, as would be most convenient for the examination of that Hypothesis.

After describing the experiment (Hooke tells us that the long arm of the J-tube was about fifty inches long), he concludes:

and by making several other tryals, in several other degrees of condensation [compression] of the Air, I found them exactly answer the former Hypothesis.

The discovery itself was significant. The measurements of the springiness of the air fed into the development of theoretical ideas about the nature of matter, leading up to the idea of atoms and molecules flying about in the vacuum and colliding with one another. It also had practical implications, because the idea of making vacuums using pistons, and using the weight of air (atmospheric pressure) to compress pistons, found applications in steam engines. But from our point of view the most important thing about these experiments is the way they were carried out and reported. For the first time, experimental philosophers described their experiments in great detail, along with the way they overcame difficulties and how they interpreted their results. They not only gave a table showing the actual measurements of pressure made in the course of the investigation, but also included alongside these the numbers corresponding to ‘What the pressure should be according to the Hypothesis’. The match was not perfect; of course there were experimental errors. But they (or rather Hooke) had found that the accuracy of the hypothesis was confirmed within the limits of experimental error. And everything was laid out carefully so that other experimenters could repeat the whole process and see if their results agreed. It was only later, when many other experiments had indeed confirmed this, that the hypothesis was elevated to the status of a law, albeit with the wrong name attached to it.

While in Oxford, Hooke also developed his interests in astronomy and timekeeping, which we have already mentioned. Some of his other activities can wait until we discuss the contents of Micrographia. But there was one interest in particular that Hooke at first eagerly investigated in Oxford but then (for sound scientific reasons) abandoned – flying. This change of heart is described in the autobiography:

I contriv’d and made many trials about the Art of flying in the Air, and moving very swift on the Land and Water, of which I shew’d several Designs to Dr. Wilkins then Warden of Wadham College, and at the same time made a Module [model], which, by the help of Springs and Wings, rais’d and sustain’d itself in the Air; but finding by my own trials, and afterwards by Calculation, that the Muscles of a Mans Body were not sufficient to do anything considerable of that kind, I apply’d my Mind to contrive a way to make artificial Muscles; divers designs wherefore I shew’d also at the same time to Dr. Wilkins, but was in many of my Trials frustrated of my expectations.

The details surrounding one other project which Hooke worked on in the late 1650s and early 1660s are less clear, because for commercial reasons (in the hope, never realised, of making a fortune from his invention) for a long time Hooke kept details of his work on clocks and watches secret, and when he did report them he was inclined to exaggerate his achievement to strengthen his case. Nevertheless, it is quite clear that by about 1658 he was deeply interested in the possibility of designing an accurate timepiece – a chronometer – that would solve the problem of finding longitude at sea. This was of vital importance to an emerging maritime power such as England or their Dutch rivals.

Finding the latitude of a ship at sea was a relatively simple matter of measuring the height of the Sun above the horizon at local noon. But determining longitude was a much more difficult problem. It was clear that the person who solved that problem would certainly become rich as a result – even before the establishment of the famous prize of £20,000 offered for the solution by the British government in 1714. Hooke was always concerned about his financial security, and looked into two ways to tackle the problem. The first was based on the idea of astronomical observations, in particular observations of the moons of Jupiter. The four largest moons (discovered by Galileo in 1610) follow regular, predictable orbits around the giant planet, changing their positions relative to one another like the hands of a heavenly clock. These orbits could be predicted from past observations, even before the discovery of the inverse square law of gravity, so by studying tables of predicted patterns (in particular, eclipses of the moons by Jupiter) and comparing them with observations, a mariner could determine the time at the place where the tables were drawn up (such as the home port, or London) and compare that with the local time. Because of the rotation of the Earth, which takes twenty-four hours to complete a 360-degree rotation, local noon is one hour later for each fifteen degrees west of the home base, and one hour earlier for each fifteen degrees east (360/24 = 15); even Oxford time, by the Sun, is five minutes behind the time at Greenwich, in London. So the difference would tell them how far east or west of home the ship was. This was one of the reasons, in addition to his interest in astronomy and the nature of the Universe (Hooke was interested in everything about how the world worked!), that Hooke devoted a great deal of time to developing improved astronomical observing instruments. But making the required accurate observations from the surface of a ship at sea, pitching and rolling in the waves, was totally impractical.

The other way of working out how far east or west of, say, London you were would be to carry ‘London time’ around with you, in the form of a clock or watch set before starting out on the voyage. But that would require a chronometer that could keep time to an accuracy of a few seconds over an interval of weeks or months. And, again, it had to do so on a ship being tossed about on the waves.

In the middle of the seventeenth century, revolutionary developments in timekeeping devices were taking place. Earlier clocks, going back to the fourteenth century, were powered by slowly falling weights, connected to the gears and wheels of the mechanism by cords wrapped around a bobbin-like drum. The drum rotated as the weight fell, and the rate at which the weights fell was controlled by a so-called verge escapement, involving a toothed ‘crown wheel’ which was tugged one step (one tooth) at a time by the pull of the falling weight. When the weight reached its lowest point, it was simply lifted (or wound) back up to keep the clock ticking. These clocks were good for measuring the passage of the hours, provided they were re-set at noon, but did not even measure minutes accurately, let alone the seconds. It was Galileo who realised that the time it takes for a pendulum to complete one swing of its arc depends only on the length of the pendulum, and the Dutch scientist Christiaan Huygens who, in 1656, used this, in conjunction with a traditional verge escapement, to produce the first reasonably accurate pendulum clock. A pendulum 39.1 inches (0.994 m) long takes one second to swing one way, and one second to swing back, at 45 degrees latitude on the surface of the Earth; at one time it was proposed that this length should be used to define the metre (making a metre 39.1 inches), but this was not followed up.^fn6 Both Huygens and Hooke set out to improve on these devices, being well aware that no matter how accurate it might be on land, a pendulum clock was hardly the most practical timepiece to have on the heaving decks of a ship.

Hooke’s key idea was to replace the regular swing of a pendulum with the regular pulse of a coiled spring, vibrating in and out. He also devised an improved escapement. The spring-driven mechanism would work in a clock, but, equally importantly, could be made small enough to be incorporated in a watch compact enough to be carried in your pocket.

This is where the historical chronology becomes murky. Hooke certainly had the idea for such a watch by 1660 (the year of the Restoration, when Charles II came to the throne). But had he made a watch to this design by then? Hooke, via Waller, tells us that he had:

Immediately after his Majesty’s Restoration, Mr. Boyle was pleased to acquaint the Lord Boucher and Sir Robert Moray with it, who advis’d me to get a Patent for the Invention, and propounded very probable ways of making considerable advantage by it. To induce them to a belief of my performance, I shew’d a Pocket-watch, accommodated with a Spring, apply’d to the Arbor of the Balance to regulate the motion thereof … this was so well approved of, that Sir Robert Moray drew me up the form of a Patent … [but] the discouragement I met with in the management of this Affair, made me desist for that time.

The discouragement to which Hooke refers is a proposed clause in the patent that says that if anyone else improved upon the design ‘he or they should have the benefit thereof during the term of the Patent, and not I’. It is hardly surprising that Hooke refused to sign away his rights in this way (as he put it, it is easy to add to an existing invention), and there the matter rested until a later dispute, as we shall see, blew up with Huygens.

We know that these events took place – a draught copy of the patent survives. But did they happen in 1660, or a little later? The surviving papers are undated, which doesn’t help. Some historians suggest that it was actually in 1663 or 1664, and that Hooke later fudged the dates in order to strengthen his case against Huygens. The most careful analysis of the papers has been carried out by Michael Wright of the Science Museum in London.^fn7 He concludes that Hooke probably mentioned the invention to Moray in 1662, and revealed the details a year or two later, with the invention then being developed further in 1664, with a timekeeper completed in the summer of 1666. We shall never know for sure, and at this distance in time the priority doesn’t matter. What matters is that Hooke certainly did invent a spring-driven pocket watch, unaided, by the early 1660s, while also working as Boyle’s assistant (including the discovery of ‘Boyle’s Law’) and carrying out his own investigations of, among other things, flying, astronomy, and the microscopy that features in the next chapter. Apart from the significance of the watch itself, which was indeed a major development, two points are noteworthy about this story. The first is the way Hooke worked on many projects at once; the second is the connection with the dramatic event of the Restoration. Both would be significant in the next phase of Hooke’s career.