by John Gribbin
Another commission did not come from the City, but could not be ignored, given Hooke’s status as a Gresham Professor. The Gresham Trustees asked for advice on the cost and design for a rebuilt Royal Exchange. In November 1666 Hooke came up with a detailed proposal for a beautiful building, with an estimated cost of under £5,000, saving money by re-using some of the old materials. The Trustees rejected the proposal and opted for a lavish new building, designed by Jermyn, which cost so much (roughly £60,000) that servicing the debt caused a decline in the once-great Mercers’ Company. The new Exchange was, however, fully open by 1672, allowing Gresham College to get back to normal. But from our point of view, what is interesting is that the skill displayed by Hooke in carrying out this commission shows that he already had a thorough grasp of architecture, the practical aspects of building, and the strength of materials.
The first practical steps towards the rebuilding of London started on 27 March 1667, financed by a tax on coal. As well as the practical need to wait for spring, nothing could be done on the ground before the appropriate legislation had been issued by Parliament; the relevant Act had received the Royal Assent on 8 February. Then, before anything could be built, the survey had to be carried out. This was a major undertaking. The surveyors – Hooke and Mills – started work with Fleet Street, which was the main route from the City to Westminster, and would be widened to about fifty feet. The surveying involved seven labourers to clear the rubble before the surveying work could take place, and six carpenters to cut the wooden stakes used to mark the boundaries. After the initial work on Fleet Street, the surveyors worked independently of one another, with Mills, as we have mentioned, soon being replaced by Oliver. Most of the work was completed by the end of 1671, and the largest individual portion was carried out by Hooke. In all, 8,394 foundations were surveyed and staked out for rebuilding; of these, 1,582 are recorded as being Hooke’s responsibility, and just over 2,800 are credited to one or other of Mills and Oliver. That leaves about 4,000 unattributed surveys. One reason that many of those are unattributed is that Hooke, unlike the other surveyors, did not hand in his surveying notebooks to the authorities, and they have disappeared; he probably retained them because he used them for making scientific notes, which he wanted to keep, as well as recording his surveys. But from other evidence (including Hooke’s diary, more of which shortly) it has been estimated that at least 1,400 of these ‘belong’ to Hooke, giving him a total of some 3,000 surveys. Cooper has estimated that for rather more than five years this work occupied Hooke for three hours a day, six days a week.
But that was not the full extent of his labours on the ground. When disputes arose during the course of building, at least one of the surveyors had to make a site visit to view the situation and resolve the difficulty, writing a report and issuing a certificate to the successful party in the dispute. The householder (or tenant) had to pay a fee for these views and certificates, part of which went to the surveyor. This kind of work did not always involve disputes between neighbours: Hooke also received fees from individuals for staking out and certifying the foundations of properties prior to building. Hooke always wrote the reports if he was involved in the views, even if another surveyor also took part, and it seems that he also collected the fees on behalf of the City, and passed the appropriate share on to the other surveyor if they had been involved (among the characteristics that made Hooke so valuable to the City were his scrupulous honesty and accurate record-keeping). This work continued intermittently long after the fire. In a diary entry dated 6 May 1693, Hooke refers to a meeting with Oliver at Jonathan’s coffee house:
I paid J. Oliv. for yesterdays View 10 [shillings]. Viewed it again with J.O. I drew Report at Jonathan’s, we both signed it.
So Hooke, more than anyone, was responsible for ensuring that building regulations were obeyed and that the new city took on the appearance that it did. Hooke made at lest 500 views of new buildings himself, mostly between 1668 and 1674, earning at least £1,600 in fees for the reports and payments for certificates issued to property owners and tenants allowing them to begin work, or to claim compensation for land lost to improvements such as road widening. By the end of 1671, more than 7,000 houses had been built, and the city was getting back to normal, but now with brick buildings, wider roads, new marketplaces, and the gradients of the steeper hills eased. If Hooke had made no other contribution to the rebuilding, his major contribution to this would be a staggering achievement worthy of far more recognition than it has generally received. But he did do more, in a collaboration with Wren, who has sometimes overshadowed his contribution to city planning almost as effectively as Isaac Newton overshadowed his contribution to science, but without Newton’s malicious intent.
There are four aspects of Hooke’s work with Wren that are particularly impressive, ranging from the practical to the sublime.fn10 The practical project involved restoring the Fleet Stream from its state as a refuse-filled ditch to a navigable river or canal; the fact that for reasons beyond the control of the architects it later fell back into decay does not detract from their achievement.
By 1666 the Fleet was accurately described by the common name of the Fleet Ditch, although it had once been a channel that could be navigated at high tide from the Thames to Holborn Bridge. If the city was being rebuilt anyway, surely here was an opportunity to restore the river to its former glory, canalising it and providing broad quays for unloading goods. The project, which on the City side was largely promoted by Sir John Lawrence, was assigned to Hooke and Wren, who made detailed proposals, which were approved by the City in March 1671. The project was beset by many problems, not least the fact that although it was easy to clear rubbish from the ditch and start digging, it soon filled up again with detritus carried by runoff from rainfall down the steep sides of the little valley in which the stream lay. In addition, since the remit of the City only extended as far as Holborn Bridge, there was nothing to stop people further upstream continuing to dump their household refuse, industrial waste, slaughterhouse offal and other unsavoury items into the water to be carried downstream, and although gratings were built to hold back this flow, they often broke under the pressure.
In spite of all the difficulties, the project was completed by the autumn of 1674, at a cost of £51,307 6s 2d. It was intended to recoup the cost of maintaining the canal by charging tolls for the use of the quays by barges, but it turned out to be quicker (and cheaper!) for barges to be unloaded at the river and goods to be transported inland by carts. Indeed, the broad quays lining the Fleet Canal (as it now was) became used as highways for wheeled traffic heading north and south. The canal fell into disrepair and once again the Fleet became filled with silt and rubbish; it was eventually (in 1769) covered by a road, but the Fleet still flows underground beneath Farringdon Street and New Bridge Street.
Hooke was also involved in other civic works, not least laying pipes to bring fresh water to the population, and sewers to remove waste. But the second achievement of the Wren–Hooke partnership that we want to mention is a well-known one, but in which Hooke’s role is usually greatly underestimated. We refer, of course, to the rebuilding of London’s churches.
The authorities responsible for the rebuilding of parish churches, appointed by Parliament, were the Archbishop of Canterbury, the Bishop of London and the Lord Mayor; they became known as the Commissioners for Churches, although this was not an official title. In their turn, in 1670 they put Wren in charge of the design and construction of the churches, with Hooke and Edward Woodroofe named as his assistants. Woodroofe was already working with Wren as his assistant on the St Paul’s project, and did little work on the churches; he died in 1675 and was replaced by John Oliver, who was the kind of assistant that the term usually implies. The working relationship between Wren and Hooke was, however, much closer and more equal than the term ‘assistant’ usually implies. The notion that Hooke was not involved in the design of the buildings, but merely supervised the construction following Wren’s or
ders, stems from a book, Paternalia, written by Wren’s son and published in 1750, which plays Wren’s role up and Hooke’s role down. But modern (unbiased) authorities have a quite different view: in modern terms, it would be better to regard Hooke as a junior partner in Wren’s architectural firm, although not much the junior.
Although most of the parish churches were built of stone, many suffered severely in the fire, with burnt-out interiors, collapsed roofs, damaged steeples and unstable walls. Out of 110 churches, twenty survived the fire, thirty-five were demolished and not rebuilt, and fifty-five were pulled down and rebuilt. But this programme of rebuilding did not begin immediately after the fire, partly because of the cost and partly because of the pressing need to rehouse the people of the City (in the interim, they worshipped in temporary wooden chapels). The money was raised following an Act of Parliament in 1670, imposing a further tax on coal for this specific project. The work continued until 1695, alongside Wren’s work on other projects, including St Paul’s, and it is impossible that he could have been responsible for all of the design work. A handful of churches, notably St Benet Paul’s Wharf (probably the best surviving example in London if you want to see what a Hooke church looks like), St Edmund the King, St Martin within Ludgate and St Michael’s Crooked Lane, are now confidently identified as largely or solely Hooke’s work, and many others were likely to have been chiefly his or a result of a collaboration with Wren. On the other hand, the documentary evidence cannot unambiguously identify Wren as the sole or chief ‘author’ of more than half a dozen of the churches. Most of the churches have little or no documentation and there is no way to tell for certain from other evidence who worked on them, but Hooke seems to have been influenced by Dutch design, which has helped in the attribution of some of the rest. Partly on this basis, in his book The City Churches of Sir Christopher Wren Paul Jeffery argues that Hooke and Wren divided the City up between them, roughly fifty–fifty, with Hooke attending to churches in the north and east (near to his base at Gresham College) and Wren concentrating on the south and west. This seemingly plausible division of labour into rough, if not exact, equality has been questioned, but, coming as it does from an author writing in praise of Wren rather than Hooke, it has to be taken seriously. It also matches the equal division of responsibility between Hooke and Wren in their collaborations on astronomy and other scientific work.
The most compelling evidence, though, is financial. Between 1671 and 1693 Hooke was paid a total of £2,820 from the fund for ‘Officers and Servants Emploid in Building Parochiall Churches’. This is more than the combined income he received as Gresham Professor and as City Surveyor, and far more than he would have earned merely by supervising the work on the ground. As Stephen Inwood has pointed out, we can only conclude ‘that his career as a City church builder was as important as his career as a scientist, a lecturer, or a City Surveyor.’
Hooke certainly had a high and justified contemporary reputation as an architect, and received several significant private commissions. Among the most important of these were: the Bethlehem Royal Hospital (known as ‘Bedlam’) for the mentally ill, in Moorfields; Aske’s Hospital, in Hoxton; Merchant Taylor’s School, in Suffolk Lane; the College (later Royal College) of Physicians, in Warwick Lane; Bridewell Hospital; and (by no means least) Montagu House, in Bloomsbury. None of these survives. Outside London, some of Hooke’s buildings do still stand: the almshouses commissioned by Seth Ward in Huntingdon; Ragley Hall, in Warwickshire; Ramsbury Manor, in Wiltshire; Sheffield Place, in Essex; and our favourite, the little church he built for Richard Busby at Willen, in Buckinghamshire. Even this is not an exhaustive list, and Cooper has estimated that in addition to the salary he received for his work on the city churches Hooke received about £2,000 for his private architectural and building commissions, giving a total income from all this kind of work of nearly £5,000, equivalent in purchasing power to several million pounds today. But science was still Hooke’s enduring interest, as is shown by the design of one building in London that is undoubtedly his own work, even though the plaque that is on it wrongly attributes it to Wren – the Monument.
The third of Hooke’s great achievements resulting from the Fire, the Monument is a hollow memorial pillar near the site of the outbreak of the Fire, 15 feet in diameter and 120 feet high, standing on a square plinth and surmounted by a representation of a flaming urn, giving a total height of 202 feet. This makes it 33 feet taller than Nelson’s Column in Trafalgar Square. Made of Portland stone, the Monument was built to commemorate the recovery of the city from the Fire, rather than as a memorial to the Fire itself, so the project only got under way once that recovery was assured. The paperwork for Hooke’s design, approved and signed by Wren on behalf of the King, survives, so its authorship is undisputed, although Wren worked with Hooke on practical aspects of the construction, ensuring that it could be used as an astronomical telescope and as a vertical laboratory for carrying out experiments involving gravity. This represented a brilliant application of what ended up as a cost of £13,450 11s 9d from the coal fund – a sum that would never have been devoted to pure scientific research. Lisa Jardinefn11 has said that the Monument ‘stands out for the fully realised nature of its double function as both architectural monument and oversized scientific instrument.’
The site for the Monument was available because it was decided not to rebuild St Margaret’s Church in Fish Street, but to merge the parish with the adjacent St Magnus the Martyr. Permission was formally given to demolish the remains of the old church on 3 August 1670, and on 26 January 1671 the Court of Aldermen approved Hooke’s design:
Upon view of the draught now produced by Mr Hooke one of the Surveyors of new buildings of the Pillar to be erected in memory of the Late dismall Fire the same was well Liked and approved. And it is referred to the said Surveyors to estimate and certify unto thus Court the charge of the said Pillar.
Detailed design work and the legal acquisition of the land by the City took many months, so it was not until October 1672 that orders were issued to enclose the land required for the building site and work could begin. Hooke kept a careful eye on progress, in between his many other commitments, but the main structure was not completed until October 1676, with a modest official opening ceremony on 17 November that year. Sorting out the accounts and settling all the payments to contractors took more months, with Hooke closely involved, but what we are interested in here is how the Monument was intended (and used) for scientific work. To this end, Hooke took meticulous care to ensure that the Monument was built on solid foundations, dug into a bed of gravel six feet thick; that the height of each of the 311 steps leading to a viewing platform at the top, like the staircase of a lighthouse, was accurately monitored at exactly six inches;fn12 and that the pillar was truly vertical with an even interior diameter. No wonder it took so long to build and cost so much. And no wonder it still stands!
Hooke’s chief hope was that he would be able to use the vertical tube of the pillar as a telescope to observe stars directly overhead (at the zenith), and measure the apparent shift in the positions of these stars as the Earth moved around the Sun. This parallax effect is exactly the same as the way in which if you hold a finger out at arm’s length and shut each of your eyes in turn the finger seems to move against the background. Hooke had previously tried to measure this by observing from his rooms in Gresham College, using a tubeless ‘telescope’ made by putting one lens in a circular hole in the roof, with another lens supported directly below it, but the difficulty of lining the lenses up and the vibrations that shook the building made this a hopeless task. The Monument was much better suited to the job, with an objective lens mounted under a hinged lid incorporated into the flaming urn at the top, and a second lens, the eyepiece, in an underground chamber (a large laboratory) below the pillar, where Hooke (or some other observer) could lie on his back to observe. The technique was sound, and astronomical parallax can indeed be measured, but the differences are so small that with the t
echnology available to him even the ingenious Hooke could not detect them – the first measurements of stellar parallax were not in fact made until the 1830s.
Hooke also carried out experiments to measure the air pressure at different heights up the pillar, but these only confirmed what was already known from taking barometers up and down hills, or inside tall buildings such as the old St Paul’s Cathedral. Gravity experiments involved dropping objects from different heights inside the pillar and timing their fall, weighing things at different heights, and work with pendulums. No dramatic discoveries were made, but these are all examples of the busy Hooke taking every opportunity, and making new opportunities, to test hypotheses directly by experiment – nullius in verba.
Although long misattributed to Wren, in recent times the Monument has often been described as the most visible and appropriate monument to Hooke the architect – at least, the most prominent such memorial in London. But there is something even more impressive, the fourth of his great architectural achievements to which we want to draw attention.
In the course of his work as a surveyor, architect, and supervisor of building work after the Fire, Hooke was responsible for ensuring that the new buildings were structurally sound and capable of bearing the loads put upon them. He became intrigued by the puzzle of finding the best possible shape for an arch, requiring the least amount of building materials for the most strength of the structure. Hooke was the first person to realise that this optimum shape is just the inversion of the curve formed by a chain hanging between two points. Gravity pulling down on the chain produces a tension that shapes the chain into what is called a catenary curve. If you imagine the chain being set rigid and then turned upside down to make an arch, the forces are reversed to become compression forces, the mirror image of the original forces, and this shape, it turns out, provides the greatest strength for an arch – an inverted catenary. With his architectural work now contributing to his scientific work, Hooke described the discovery to a meeting of the Royal in December 1670, although clearly he had been aware of it for some time, and had discussed it with his colleague Christopher Wren. Exactly a year later, on 7 December 1671, he presented a more detailed description, recorded in the Royal Society’s archive: