Out of the Shadow of a Giant

by John Gribbin

  It is probable that Hooke’s regimen was ultimately fatal, and that even before it killed him the side-effects of his medicines (clouded vision, giddiness, lassitude, melancholy) proved damaging and disabling.fn5

  Less dramatically, others have argued that the symptoms described by Waller suggest a congestive heart failure, with the circulation of the blood becoming so weak that the extremity of the body, in particular the legs, ‘swells with retention of fluid, constricting circulation even further.’fn6 In any case, in his final year Hooke was all but bedridden, attended by a maidservant, and suffering breathing difficulties as well as the swelling of his legs. The end came in March 1703, in his sixty-ninth year, as reported by Knox:fn7

  The 2th March 1702/3 This night about 11 or 12 of the Clock my Esteemed Friend Dr Robert Hooke Professor of Geometry & Naturall Philosophy in Gresham College Died there, onely present a Girle that wayted one him who by his order (just before he died) came to my Lodging & called me. I went with her to the Colledge where, with Mr Hunt the Repository Keeper, we layed out his body in his Cloaths, Goune & Shooes as he Died, & sealed up all the Doores of his apartment with my Seale & so left them.

  Hooke was buried with due ceremony at St Helens (near Tom Giles and Grace Hooke); as Waller put it, ‘decently and handsomely interr’d in the Church of St. Hellen in London, all the members of the Royal Society then in Town attending his Body to the Grave, paying the Respect due to his extraordinary Merit’. But the location of his remains and those of his kin were lost during rebuilding work in the nineteenth century. There is, however, a stylised representation of him (far from true to life!) in the stained-glass window at the west end of the church. Hooke left no will, in spite of having talked of making a bequest to the Royal, and his material inheritance became the subject of an unseemly quarrel among his distant relatives, which need not concern us here. But there was plenty to quarrel about – more than £8,000 in cash, plus some gold, jewellery, and valuable books, as well as the usual personal effects.

  Hooke’s real legacy, of course, was his contribution to science. So rather than concluding the story of his life with its rather depressing end, we will summarise one of his lifelong scientific themes, which also happened to be the last topic of major scientific significance with which he addressed the Royal Society: the nature of fossils, the age of the Earth, and the evolution of life.

  The definitive study of Hooke as a geologist has been carried out by Ellen Tan Drake, of Oregon State University, and published, along with Hooke’s lectures on ‘earthquakes’ (a term he used to embrace all changes in the surface of the Earth including volcanic eruptions) in her authoritative book Restless Genius. We follow her presentation here, and the quotes from Hooke are taken from the transcriptions included in her book, which provides the most easily accessible and complete compilation of what Drake refers to as Hooke’s ‘earthly thoughts’.

  Hooke gave several series of lectures on ‘earthquakes’ over an interval of more than twenty years. There is a considerable amount of repetition and overlap in the lectures, and some digressions where Hooke cannot resist wandering off the subject to discuss some other phenomenon. So we have selected quotes from different lectures, not always following the chronological sequence in which the talks were given, in order to make Hooke’s thinking clear. But his main themes are indeed clear, and astonishingly modern.fn8 It is also clear, as Drake has spelled out, that Hooke’s thoughts on geophysics, as it is now called, were a direct influence on later Earth scientists, including James Hutton, who is widely regarded as the father of geology.

  As we have mentioned, Hooke’s boyhood on the Isle of Wight was of fundamental importance to his interest in geology, and he often used examples from the island to illustrate his ideas, at least as early as in Micrographia. In that book, he provided the first drawing of a foraminifer, and described how he had found it among grains of sand, as ‘an exceedingly small white spot, no bigger than the point of a Pin’, which resembled ‘the shell of a Water-Snail, with a flat spiral Shell.’ Nobody had previously noticed the existence of such microorganisms. In one of his lectures, he refers to a stone which he ‘broke with a smart stroke of a Hammer’ with the result that he ‘discover’d two small Snake-stones within it, which probably had been tumbled into the Mouth of it before it was concreted; for they were of the very same Substance, but of a differing Figure from any I have yet describ’d’.

  Hooke explained the existence of fossils in terms of eleven ‘Propositions’, starting with the assertion that such objects were indeed the petrified remains of living things, with ‘their Pores fill’d up with some petrifying liquid Substance, whereby their Parts are, as it were, lock’d up and cemented together in their Natural Position and contexture’, and ending with the statement that ‘there have been many other Species of Creatures in former Ages’ (more of this shortly). In support of the first proposition, Hooke describes the way stalactites and stalagmites form in caves solely by the action of dripping water, ‘by which we are assured that Nature really does change Water into Stone’.

  And he gives short shrift to those who subscribe to the then popular notion, described by Hooke as ‘Astrological and Magical Fancy’, that fossils are just stones that resemble living things, people who think that:

  They were produced from some extraordinary Celestial Influence, and that the Aspects avid Positions of the fix’d Stars and Planets conduc’d to their Generation, so that they also have in them a secret Vertue whereby they do at a distance work Miracles on things of the like Shape.

  Such ideas, he says, are ‘fantastical and groundless’. He was certainly no alchemist.

  Hooke was able to make the intellectual leap from the study of such remains to genuinely scientific generalisations about the long history of the Earth. And he realised that the story of Creation told in the Bible should not be seen as literally true – unlike Newton, for example, who in a desperate attempt to reconcile observations with the story of Genesis suggested that the Earth might have rotated more slowly in the past, so that the six ‘days’ of Creation occupied a long span of time. In December 1680, he wrote to Bishop Thomas Burnet, author of The Sacred Theory of the Earth,

  … all this might ye rather bee, because at first we may suppose ye diurnal revolutions of ye Earth to have been very slow, soe yt ye first 6 revolutions or days might containe time enough for ye whole Creation …

  It doesn’t seem to have occurred to Newton to wonder what the effect of the long nights would have been on the life that existed before the job of Creation was completed with Adam and Eve. Hooke (who, by the way, realised that the rotation of the Earth was slowing down, and must have been faster in the past) had a simpler explanation. He noted that the story in the Bible was written down long after the events it purported to describe, and had previously been passed down over many generations by word of mouth, providing ample opportunity for the story to get distorted. As he put it, before the invention of writing the stories must have been ‘dark and confused’, and ‘cannot be much relied on or heeded’. Hooke was a religious man, in that he believed in God, but he was quite prepared to adjust religious ideas to fit the facts, rather than the other way around.

  One of the facts that had to be explained was the presence of shellfish fossils far from the sea – indeed, far above sea level. ‘Who can imagine that Oysters, Muscles, and Periwinkles, and the like Shell-fish, should ever have had their Habitation on the tops of the Mountain?’ And not just on mountains. Fossils are found, Hooke points out:

  At the tops of some of the highest Hills, and in the bottom of some of the deepest Mines, in the midst of Mountains and Quarries of Stone, &c.

  The reason for their presence there must be ‘the prodigious Effects that have been produced by Earthquakes on the superficial Parts of the Earth’. But he does not suggest that these were violent events that raised mountain ranges up in a single catastrophe. Rather, he refers to changes in the surface of the Earth happening bit by bit (‘by degrees’), gra
dually over, by implication, a long (very long) interval of time. ‘Those prodigious Piles of Mountains are nothing but the effects of some great Earthquakes.’ As an example, he reports descriptions of the eruption of the volcanic island of Santorini in 1650, and comments:

  Though our Natural Historians have been very scarce in the World, and consequently such Histories are very few; yet there has been no Age wherein such historians have liv’d, but has afforded them an Example of such effects of Earthquakes.fn9 And I doubt not, but had the World been always furnisht with such Historians as had been inquisitive and knowing, we should have found not only Thera or Santerinum, and Volcano and Delos, and that in the Azores, and one lately in the Canaries, but a very great part of the Islands of the whole World to have been rais’d out of the sea.

  And he says:

  Nor do I conceive they were all thus formed at once, but rather successively, some in one, some in other Ages of the World, which may probably be in some measure collected from the quantity or thickness of the Soil or Mould upon them fit for Vegetation.

  This ties in with a broader conclusion he reached:

  that a great Part of the Surface of the Earth has been since the Creation transform’d, and made of another Nature: that is, many Parts which have been Sea are now Land, and others that have been Land are now Sea; many of the Mountains have been Vales, and the Vales Mountains.

  Hooke also notes that ‘Convulsions’, as he calls them, are most common in mountainous regions, and cites Pliny, who ‘says, that the Alps, and Appennine Mountains have very often been troubled with Earthquakes’.

  All of this ties in with another key feature of Hooke’s thinking about the Earth. Although Copernicus had removed the Earth from its status as the centre of the Universe, it still seemed, especially in the light of the biblical stories, to be a place of special significance in the Universe. Hooke was the first scientist to treat the Earth simply as a planet, one member of the Sun’s family of planets, distinguished only by our presence on its surface, but subject to exactly the same laws (such as gravity) as the other planets. Newton, influenced by Hooke, only slowly came to this realisation.

  This image of the Earth in space contributed to Hooke’s ideas about polar wandering, which involves a shift in the position of the poles as seen from the surface of the Earth, or, if you prefer, a shift in the crust of the Earth relative to the poles. This is not continental drift – the continents do not move relative to one another – but involves the solid crust of the Earth moving over a more fluid interior. But it is a real effect, which is an integral part of the modern theory of plate tectonics, and has actually been measured using geological data – it occurs at a rate of about 5–10 cm per year, and at present the North Pole is moving (from our perspective) towards London. Hooke’s version invoked changes in the position of the centre of mass of the Earth, linked to geological processes. The motivation for this idea was the evidence Hooke saw from his fossil studies, including remains of tropical species found at Portland, that England had once been in what he called the ‘Torrid Zone’ and must have moved to its present position. ‘Consider, whether it may not have been possible, that this very Land of England and Portland, did, at a certain time for some Ages past, lie within the Torrid Zone.’ The package of ideas included in this concept included the Earth being more dense in the centre than at the surface (explaining why heavy metals such as gold are rare at the surface), an equatorial bulge produced by the rotation of the Earth, and the suggestion that ‘whenever an Earthquake raises up a great part of the Earth in one place it suffers another to sink in another place’. Mineral ores, he suggested, were generated deep within the Earth and had been uplifted ‘by some former Subterraneous Eruption (by which those Hills and Mountains have been made)’. While others – even the famous Steno, of whom more shortly – thought that fossil remains found on mountain tops were a result of Noah’s flood, Hooke was unique among his contemporaries in suggesting that they had been lifted up by geological activity, so that:

  the superficial Parts of the Earth have been very much changed since the beginning, that the tops of mountains have been under the Water, and consequently also, that divers parts of the bottom of the Sea have been heretofore Mountains.

  As for Noah’s flood, it might have happened, but it did not last long enough (a mere 200 days) to explain how the remains found in, for example, the Alps, had got there. Once again, biblical stories give way to scientific facts.

  It’s worth elaborating on Hooke’s ideas concerning the shape of the Earth, since Isaac Newton is still often credited with the ‘discovery’ of its oblate shape. Hooke lectured on the subject in the mid-1670s, some twelve years before Newton published his version in the Principia. Newton’s correspondence with Burnet shows that at least as late as 1681 he thought the Earth was perfectly spherical. Hooke returned to the theme in the lectures he gave late in 1686 and early in 1687, to answer criticisms he had received. He demonstrated the processes taking place in two experiments. One involved simply blowing a bubble of glass using a glass-blower’s pipe. When the pipe was held still while the molten glass set, the bubble formed a hollow sphere. But when the pipe was twirled around while the glass was setting, the resulting bubble bulged out at its ‘equator’. The second demonstration involved a bowl of water on a turntable. When the turntable was spun, the water sank in the middle and rose up the sides of the bowl. Note that this happens when the bowl and water are both rotating, so the water is not moving relative to the bowl, unlike the case of tea stirred in a cup, which also forms a concave surface. Like all good scientific ideas, this one made predictions that were confirmed by other experiments. If the Earth bulged at the equator as Hooke suggested, gravity would feel weaker there, so a pendulum clock would run slower at (or near) the equator than at European latitudes, unless the pendulum was shortened. Edmond Halley, as we have seen, observed exactly this phenomenon on his visit to St Helena. It had previously been noted by the Frenchman Jean Richer, but his results were not published until 1679, which may explain Hooke giving priority to Halley when he said in one of those lectures ‘that Phaenomena do answer to this Theory, has been verfify’d, first by Mr. Hally at St. Helena, and since by the French in Cayen …’twas necessary to shorten the Pendulum to make it keep its due Time’. Newton, however, emphasised Richer’s observations of 1672 in Book Three of the Principia, without mentioning that they were not widely known until 1679. Drake suggests that he did this to give the impression that his own views on the shape of the Earth were formed by learning of Richer’s results around that time, while the correspondence shows that he did no such thing. ‘Here,’ she writes, ‘is another example of history allowing Newton to usurp the credit that rightfully belongs to Hooke.’

  Hooke’s vision of geological processes is, as he puts it, ‘almost’ circular. Uplift is followed by erosion, with sediments being laid down to form new rock, followed by more cycles of uplift and erosion. He was what would later be called a gradualist, or uniformitarian – someone who recognises that the features of the Earth around us, especially great mountain ranges, are produced by gradual processes, the same processes we see at work today, but operating over very long intervals of time. When Charles Darwin realised, as a result of an earthquake and uplift he experienced and observed in South America during his voyage on the Beagle, that this is the way mountains are made, it was the same realisation Hooke had come to more than 150 years before. But the ‘almost’ in Hooke’s discussion of cyclic geological processes is crucially important. Hooke also realised that eventually everything wears out: the law of nature later enshrined as the second law of thermodynamics, described by the twentieth-century physicist Arthur Eddington as holding ‘the supreme position among the laws of Nature’.fn10

  ‘Cities, Countries, Shores, nay the Sea itself are the Slaves of Fate,’ says Hooke. ‘The very ground we stand on is it self unfixt . . each part changes and sinks into Ruine and Alteration’.

  Late in his life, in a lecture delive
red in July 1699, Hooke referred to the ‘Subterraneous Flame or Fire, or Expression, call it by any name you please’ that drove the geological cycles, and expressly said that in time the fuel for this flame would be ‘consumed and converted to another Substance, not fit to produce any more the same Effect.’ He foresaw what nineteenth-century thermodynamicists would call ‘the heat death of the Universe’.

  Hooke’s ideas concerning the origin of the Earth and its early history evoked ‘sliding, subsiding, sinking and changing of the Internal Parts of the Earth’ as a result of which ‘many submarine Regions must become dry Land, and many other Lands will be overflown by the Sea’. This offered an explanation not just of the location of marine fossils today, but possibly also of Noah’s flood. This ‘terraqueous globe’ idea did not catch on when Hooke presented it in front of the Royal Society in the early 1660s, but surfaced in a curious way nearly thirty years later.

  John Aubrey, who was a good friend of Hooke, was so taken with the idea that when he wrote his Memoires of Natural Remarques in the County of Wilts in the 1680s he included a chapter on ‘An Hypothesis of the Terraqueous Globe’, subtitled ‘A Digression’. He identified Hooke as the originator of the idea, but noted that it had been ‘by many perhaps forgotten’, so that ‘I doe here hand [it] downe to Posterity (if this Essay of mine lives) with a due acknowledgement of his great Discovery’. In 1691, Aubrey sent a copy of the manuscript to the naturalist John Ray, the person who established the concept of species, for his advice about publishing it. Ray replied that he liked what Aubrey had written, but thought that the ‘Digression’ was ‘aliene from your subject, & so may very well be left out’. Aubrey clearly disagreed. He wrote on the letter ‘This Hypothesis is Mr. Hooks. I say so, and it is the best thing in the Book’.fn11 Aubrey’s book did not appear in his lifetime – it was eventually published as Natural History of Wiltshire in 1874, without the chapter on the Terraqueous Globe, a decision made by the posthumous editor, not by Aubrey. But in 1692, less than a year after he had read Aubrey’s manuscript, Ray rushed into print his own Miscellaneous Discourses Concerning the Dissolution and Changes of the World, which was with the printer in January 1692. It contained the text of a sermon he had preached thirty years earlier, an ‘explanation’ of fossils as stones formed by the Deluge, not the remains of living things, and a Digression (his term) on the development of the early Earth which followed the same lines as Hooke’s Terraqueous Globe idea, and cited the same references. But it did not cite Hooke. Aubrey was incensed, and wrote to a friend, Anthony Wood: