Out of the Shadow of a Giant
Page 4
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.
CHAPTER TWO
THE MOST INGENIOUS BOOK THAT EVER I READ IN MY LIFE
At the end of the 1650s, England was once again plunged into political turmoil. Oliver Cromwell died on 3 September 1658, and was succeeded by his son Richard, a less competent administrator unable to cope with a Commonwealth that was already in difficulties, with mounting debts and rival factions. In April 1659 Richard was pushed aside and the army took over, raising the prospect of another civil war. Many people who were in a position to do so, Hooke among them, started to make contingency plans. Hooke’s youthful imagination had been caught by the sight of the ships entering and leaving Yarmouth, and he now began to consider life as an adventurer and explorer travelling to the Far East. In May 1659, still not yet twenty-four years old, he read a book, Itenerario, wri
tten by a Dutch traveller, Jan van Linschoten, and made notes, which survive, about the kind of life he could expect if he followed in van Linschoten’s wake. He took particular note of the attractions of China, where ‘Schollars are highly esteemed’. But before Hooke’s plans could come to fruition – if they were ever more than a pipe dream – in the spring of 1660 Charles II was welcomed back to England, and the monarchy was restored. A wave of optimism swept the country, and Hooke, from the staunchly Royalist Isle of Wight, abandoned his plans to travel and looked forward to a future in England, where he was securely established with Boyle and had a growing reputation among the wider circle of experimental philosophers. He published his first scientific paper (as we would now call it), on capillary action, in 1661. But by then, the centre of experimental philosophy was shifting from Oxford to London.
More precisely, the scientific activity was centred around an institution known as Gresham College, in the City of London (the edifice known as Tower 42 now stands on the site, between Broad Street and Bishopsgate). In Hooke’s day, the building on that site was a large Elizabethan mansion, once owned by a wealthy merchant, Thomas Gresham. A range of buildings surrounded a square courtyard roughly a hundred yards across. Gresham had died in 1579, and left the income from his investments to have the house converted into a college and to pay for the appointment of seven ‘professors’ in perpetuity. The professors would be provided with an income of £50 a year for life, and rooms in the college, in return for giving lectures in their specialist subjects once a week in term time. The specialist subjects chosen by Gresham were law, physic (medicine), divinity, rhetoric, music, chemistry and astronomy. The professors were also required to be celibate, although as we shall see the interpretation of this term was rather loose. The status of these posts has waxed and waned over the years, but there are still Gresham Professors giving lectures, even though they no longer have a college to live in.
Hooke’s Oxford friend, Christopher Wren, had become the Gresham Professor of Astronomy in 1657, a post he held until 1661, when he returned to Oxford as Savilian Professor of Astronomy. Other experimental philosophers based in, or visiting, London (and crucially including Wilkins, who had become the Master of Trinity College in Cambridge in 1659, but was ejected when the Royalists returned to power, and was now lodging with a friend in Gray’s Inn) used to attend Wren’s lectures, and got into the habit of meeting up afterwards to discuss the topics raised and other scientific matters. On 28 November 1660, after one of Wren’s lectures, the group decided (clearly by prior arrangement) to formalise these gatherings. A record in the Royal Society archive reads:
Memorandum November 28, 1660. These persons following according to the custom of most of them, met together at Gresham College to hear Mr Wren’s lecture, viz. the Lord Brouncker, Mr Boyle, Mr Bruce, Sir Richard Moray, Sir Paule Neile, Dr Wilkins, Dr Goddard, Dr Petty, Mr Ball, Mr Rooke, Mr Wren. And after the lecture was ended they did according to the usual manner, withdraw for mutual converse.
That ‘mutual converse’ led to the resolution that they would form an association ‘for the promoting of Experimentall Philosophy’ and:
That this company would continue their weekly meetings on Wednesday, at 3 of the clock in the term time, at Mr Rooke’s chamber at Gresham College; in the vacation at Mr Ball’s chamber in the Temple, and towards the defraying of expenses, every one should, at his first admission, pay downe ten shillings and besides engage to pay one shilling weekly … Dr Wilkins was appointed to the Chair, Mr Ball to be Treasurer, and Mr Croone, though absent, was named the Registrar.
This was the beginning of the Royal Society, whose members became known as ‘Fellows’. Because of Wilkins’ reputation as a Parliamentarian, it became politic for him to take a back seat (at least formally), and Sir Robert Moray was installed as President of the fledgling association on 6 March 1661. In no small measure thanks to his skill at political wheeling and dealing, the Society gained its first Royal Charter in 1662, with Brouncker now named as President, but this Charter proved unsatisfactory (for obscure reasons), and was replaced by a second Charter in 1663, formalising the name as ‘the Royal Society of London for Promoting Natural Knowledge’.fn1 The Society had a coat of arms, and a motto, Nullius in Verba, which can be translated as ‘take nobody’s word for it’. In other words, carry out experiments and test hypotheses for yourself, do not rely on hearsay. It would be Hooke who soon put that fine sentiment into practice. We shall always refer to the institution as the Royal Society (even for the period before the award of the first charter), the Royal, or the Society; one of the aims of seeking royal status was to get financial support from the King, which was never forthcoming, but the status did encourage rich dilettantes to offer their support, if only by becoming Fellows and (sometimes) paying their subscriptions.
As early as December 1660, the Society laid out the ground rules for doing experiments, and recognised the need for ‘curators’ who would carry out the experiments. At first, this role was carried out by the most expert Fellows (known as virtuosi), but this was not a success, and it became clear that they needed somebody who could do the job full time. In the early 1660s, Boyle was spending some of his time in Oxford and part at his sister’s house in London, where he had a laboratory. Hooke accompanied him and was well known to the Fellows (his little paper on capillary action is mentioned in their records). By 1661, Boyle and Hooke were developing an improved air pump, and Boyle gave their original pump to the Royal, where it languished with nobody able to operate it satisfactorily. This was another indication of the need for a skilled curator who could make things work. And who better than the man who had designed and built that pump?
So on 12 November 1662 Sir Robert Moray proposed, and the Fellows accepted, that Hooke should be appointed Curator of Experiments ‘to furnish them every day when they met, with three or four considerable Experiments’, as well as following up topics for investigation suggested by the Fellows. The only snag was, the Royal did not have any funds with which to pay him. The solution was that in effect Boyle ‘lent’ Hooke to the Royal Society until 1665, when a combination of circumstances (not all of them straightforwardly honest) stabilised the situation.
The Royal had notionally set Hooke’s salary as £80 a year, even though they were not paying it. Nor were they able to provide him with accommodation, so he had to make do with temporary lodgings. Partly as compensation, in recognition of his value he was elected as a Fellow of the Royal Society on 5 June 1663, with all the usual fees and subscriptions being waived. The prospect of establishing the relationship on a proper basis came in May 1664, when Isaac Barrow (the successor to the Laurence Rooke in whose rooms the Royal had its early meetings) resigned his post as Gresham Professor of Geometry to become the first Lucasian Professor of Mathematics in Cambridge (where he came across a student called Isaac Newton, who later became the second Lucasian Professor). Before he left for Cambridge, Barrow had been giving some of the astronomy lectures in place of Dr Walter Pope, Wren’s successor, who was temporarily away from London. After Barrow left, Hooke took on those temporary duties, and received the appropriate stipend, while Pope was away. Who better to be Barrow’s replacement?
There were two candidates for the post: Hooke, who had strong support from the Royal, and a physician, Arthur Dacres. On 20 May 1664, a committee (‘The Court’) met to decide between them, and duly announced their verdict:
two learned persons viz. Dr Arthur Dacres and Mr Robert Hooke being suited for the same, their petitiones being Read their ample Certificates considered and the matter debated The Court proceeded to election and made thereof the said Dr Dacres to supply the said place of Geometry Reader in the College.
A few days later, perhaps while drowning his sorrows, Hooke bumped into a wealthy merchant, Sir John Cutler, in a public house. He knew Cutler through a mutual friend, and gloomily recounted the tale. Cutler’s response was to tell Hooke to cheer up, because he, Cutler, would provide the financial support Hooke neede
d by creating a post for him to lecture on the History of Trades, at the same remuneration as a Gresham Professor – £50 a year. Before the arrangement could be formalised, however, the Royal Society got wind of some irregularities surrounding the appointment of Dacres. It turned out that the actual committee had voted for Hooke by five to four, but that the Lord Mayor of London, Sir Anthony Bateman, who was present as an observer but not a member of the committee, then voted for Dacres, making a tie, and followed this up by claiming the right to a casting vote in favour of his man. Bateman’s term as Lord Mayor came to an end shortly after this fiasco, and he was succeeded by Sir John Lawrence, a more straightforwardly honest man who knew Hooke’s abilities. Following formal representations by the Royal, a committee of investigation chaired by Sir John met on 20 March 1665 and concluded:
that Robert Hooke was the person legally elected and accordingly ought to enjoy the same with the Lodgings profits and all accommodation to the place of Geometry Reader appertaining.
In the months before the appeal was heard, the Royal acted with underhand cunning to secure the benefits of Cutler’s offer for themselves. On 27 July 1664, the Council of the Royal formally voted to appoint Hooke as Curator of Experiments with a salary of £80 a year, but kept this secret while they negotiated ‘on Hooke’s behalf’ with Cutler. It was agreed that Hooke would give what became known as the Cutlerian Lectures, on practical applications of science ‘to the advancement of art and nature’ but on specific topics chosen by the Royal. And Cutler’s money would be funnelled to Hooke through the Royal. So when Hooke was formally appointed as Curator on 11 January 1665, the Royal only had to add £30 a year for his income to be made up to the promised £80. The situation was compounded when Cutler (possibly piqued by this, or maybe just unreliable) failed to pay his share most of the time, leading to tedious legal hassles only resolved in Hooke’s favour after Cutler’s death, in 1696 (for the first ten years, the Royal also had trouble finding the money to pay their contribution to his salary). But still, as he did get the Gresham chair Hooke was reasonably comfortable from the time he was installed as Gresham Professor in March 1665 (he had actually been lodging in rooms in the College since the previous September). As well as the income, he had a parlour, library and two smaller rooms in a first-floor apartment, a workshop on the ground floor, cellar rooms providing further space for his experimental work, and a garret for a servant. He was able to keep at least one servant, usually a girl, and usually on more than friendly terms, as we discuss later. He was a gregarious and friendly man (at least until old age and infirmity made him more grumpy), who welcomed visitors to his home, as well as mingling with his friends in the coffee houses. At the age of twenty-nine, he was settled for life, with no need of patronage.