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CHAPTER 1

The Man who Walks with Henslow

Charles Robert Darwin was born at The Mount, Shrewsbury, on 12 February 1809, the second son and fifth child of Dr Robert Waring Darwin.

His genetic make-up in the male line was strongly scientific, although his father combined a position as one of the leading physicians in the Midlands not with science, but with acting widely as a private financial adviser to the gentry of the region. Charles would later have high praise for his father’s powers of observation, and for his sympathy with his patients, but considered that his mind was not truly scientific. Robert’s wealth was nevertheless as valuable an inheritance for his son as a gene for science, not only paying for Charles’s board and lodging on the Beagle when he sailed as an unofficial scientist and companion to the Captain, but also enabling him to pursue a scientific career single-mindedly for the rest of his life, without ever having to earn his living.

However, his grandfathers, Dr Erasmus Darwin of Lichfield and Josiah Wedgwood I the potter, who built a model factory at Etruria near Stoke-on-Trent, were two of the leading scientists and technologists of their time. Both Fellows of the Royal Society, they were also founding members of the Lunar Society of Birmingham, which played the principal intellectual part in the establishment of the Industrial Revolution in England. Erasmus Darwin¹⁹ was primarily a practising physician, but his prodigious energies overflowed in many other directions, as a poet, an inventor of mechanical devices of various kinds, a pioneer in meteorology and in the description of photosynthesis, and not least as author of an immense medical treatise entitled Zoonomia,* and of a fine poem, The Temple of Nature, in which as we shall see he made an important contribution to his grandson’s Theory of Evolution. Josiah Wedgwood I made radical improvements in the handling of china clay, founded a famous pottery, and developed a canal system for the transport of his products. The chemists of Europe came to him for their glassware and retorts, and in due course his son Josiah Wedgwood II provided his nephews Erasmus and Charles with fireproof china dishes manufactured at the pottery, and an industrial thermometer for their private laboratory.

Charles recorded that at a very early age he had a passion for collecting ‘all sorts of things, shells, seals, franks, coins, and minerals … which leads a man to be a systematic naturalist, a virtuoso or a miser’. Throughout his life he also exercised a scientifically useful taste for making careful lists, whether of his various collections, of the game that he had killed, of books that he had read or intended to read, of the pros and cons of marriage, or of his household accounts.

During his formal education at Shrewsbury School, where like his elder brother Erasmus he boarded for some years, he was taught mainly classics, ancient geography and history, and a little mathematics, but there was no place for science in the curriculum. However, their grandfathers’ strong interest in chemistry managed to break through in both boys, first in Erasmus and then in Charles, and together they set up in an outhouse at home what they grandly called their ‘Laboratory’. Here they could pursue a hobby fashionable at the time in the upper classes for investigating the composition of various domestic materials, sometimes after purification of their constituents by crystallisation, though they were seldom able to extract sufficient funds from their father to provide any really sophisticated chemical apparatus. For a while the application of elementary crystallography to his collection of rocks and stones was one of Charles’s favourite occupations.

In 1822 Erasmus left school, and was sent to study at Cambridge, where he wrote a helpful series of letters to Charles with detailed instructions for further experiments. This encouraged Charles to examine the effect on different substances of heating them over an open flame, sometimes with a blow-pipe at the gaslight in his bedroom at school, earning him the nickname of ‘Gas’ and the strong disapproval of the headmaster. Over this period, Charles delighted in devising simple instruments for performance of his tests, and under the tuition of Erasmus served a useful initial apprenticeship in the art of scientific experimentation.

Robert Darwin now decided that Erasmus should proceed from Cambridge to Edinburgh University as he had done himself in order to take an M.B. degree, and that Charles should leave school at the age of sixteen and accompany his brother to Edinburgh in October 1825 with the same object. The plan did not quite work out, for although Erasmus did eventually pass the Cambridge M.B. exam in 1828, his poor health led to his retirement to London as a gentleman of leisure, and he never practised. Charles, on the other hand, having signed up for the traditional courses on anatomy, surgery, the practice of physic, and materia medica, the remedial substances used in medicine, which his father and grandfather had taken in their day, soon found that many of the lectures were now sadly out of date, and that conditions in the dissecting room and on two occasions in the operating room were so highly distasteful that he felt unable to continue on the course. It was not until the end of his second year that he was at last able to confess to his father his determination to abandon medicine as a career, but in the meantime Edinburgh provided other avenues to fill his time that assisted materially in his development as a scientist.

During his first year at Edinburgh, Charles took regular walks with Erasmus on the shores of the Firth of Forth, where he made his first acquaintance with some of the marine animals that later occupied him so intensively on the Beagle. At the same time he maintained his interest in ornithology, and arranged to have lessons on stuffing birds from a ‘blackamoor’ who had been taught taxidermy by the naturalist Charles Waterton. He and Erasmus also revived their knowledge of chemistry and related areas of geology by attending the stimulating lectures and demonstrations given by Thomas Charles Hope, Professor of Chemistry in the university from 1799 to 1843.

In 1826, Erasmus had remained at home, and Charles was left to fend for himself. He attended Robert Jameson’s popular series of extracurricular lectures covering meteorology, hydrography, mineralogy, geology, botany and zoology, but said many years later that ‘they were incredibly dull. The sole effect they produced on me was the determination never as long as I lived to read a book on Geology or in any way to study the science.’ Although it was true that Jameson’s style of lecturing did not inspire his audience, Charles’s copy of Jameson’s Manual of Mineralogy is heavily annotated, and provided him with a valuable source of practical information for his subsequent geological studies. He also benefited from exposure to the critical clash between Hope’s Huttonian views and Jameson’s preference for the Wernerian doctrine,^* soon coming down firmly on Hope’s side. In any case, any temporary prejudice that Charles may have had against geology did not last long, and in due course was banished by Professors Henslow and Sedgwick after his arrival at Cambridge.

In November, Charles became a member of the Plinian Society, named after Pliny the Elder, author of a famous account of the natural history of ancient Rome, at which a small group of undergraduates would meet informally for discussions of natural history or sometimes to go on collecting expeditions, but from participation in which the university professors were traditionally banned. He was also taken as a guest from time to time to the august Wernerian Society, whose membership was restricted to graduates, and whose proceedings were published in a series of learned memoirs. At a meeting of the Wernerian Society on 16 December 1826, he listened attentively to a paper on the buzzard in which the great American ornithologist and artist John James Audubon, who had recently arrived in Edinburgh to find an engraver for the first ten plates of his Birds of America, exploded the currently fashionable view of the extraordinary power of smelling possessed by vultures. When nine years later Charles was making observations in Chile on the behaviour of condors, he was happy to find himself in agreement with Audubon’s conclusions.

The senior member of the Plinian Society was at that time Robert Grant, then aged thirty-three and a mere lecturer on invertebrate animals at an extramural anatomy school, who had graduated as a doctor in 1814, travelled extensively on the Continent, and studied in Paris with the zoologist and anatomist Georges Cuvier (1769–1832). Soon Charles was taken by Grant to collect a variety of animals along the shores in the neighbourhood of Leith, and to go out with fishermen on the waters of the Firth of Forth. On these trips he was sometimes accompanied by another medical student, John Coldstream, who later advised him helpfully about fishing nets. Grant also taught Charles how to dissect specimens under sea water with the aid of a crude single-lens microscope, and gave him a valuable training in marine biology, with an emphasis on the importance of developmental studies on invertebrates, which was taken up with enthusiasm by a pupil who all too quickly outshone his master.

Among Grant’s favourite subjects for research were the not very glamorous ‘moss animals’ of genus Flustra that encrusted the tidal rocks in bunches like a miniature seaweed, and which consisted of large numbers of microscopic polyps whose precise relationship with one another was unclear. There had long been controversy as to whether they should be classified as animals or plants, and the Swedish botanist and founder of the system of binomial nomenclature of species Carl Linnaeus (1707–78) had christened them Zoophyta, an intermediate form. By the beginning of the nineteenth century it had been widely but not yet universally accepted that these organisms were indeed sedentary aquatic animals, which formed colonies often containing millions of individual polyps or zooids with specialised functions. In 1830 the phylum^* to which they belonged was termed Polyzoa by J. Vaughan Thompson, and nowadays the animals are classified as Bryozoa.

Charles set to work on the reproductive particles of Flustra and other marine animals, and to his great excitement confirmed Grant’s observation that the eggs of Flustra were coated with fine cilia, hairlike vibrating organs whose coordinated movements endowed the ova with some degree of motility. He also noted that the ‘sea peppercorns’ often found attached to old shells were not as previously assumed buttons of seaweed, but were the eggs of the marine leech Pontobdella muricata. This he duly reported in his first scientific paper, presented in a talk to the Plinian Society on 27 March 1827; but he had been seriously put out when three days earlier Grant read a long memoir to the Wernerian Society that included his pupil’s findings without any proper acknowledgement of their source. What had happened was later described by Charles’s daughter Henrietta:

When he was at Edinburgh he found out that the spermatozoa [ova] of things that grow on seaweed move. He rushed instantly to Prof. Grant who was working on the same subject to tell him, thinking, he wd be delighted with so curious a fact. But was confounded on being told that it was very unfair of him to work at Prof. G’s subject and in fact that he shd take it ill if my Father published it. This made a deep impression on my father and he has always expressed the strongest contempt for all such little feelings – unworthy of searchers after truth.²⁰

At around the same time, as Charles recalled long afterwards, he had a significant conversation with Grant:

He one day, when we were walking together, burst forth in high admiration of Lamarck and his views on evolution. I listened in silent astonishment, and as far as I can judge, without any effect on my mind. I had previously read the Zoonomia of my grandfather, in which similar views are maintained, but without producing any effect on me. Nevertheless it is probable that the hearing rather early in life such views maintained and praised may have favoured my upholding them under a different form in my Origin of Species. At this time I admired greatly the Zoonomia; but on reading it a second time after an interval of ten or fifteen years, I was much disappointed, the proportion of speculation being so large to the facts given.²¹

When in 1793 Jean Baptiste Pierre Antoine de Monet de Lamarck was appointed as Professor of the ‘inferior animals’ in Paris, he earned good marks for renaming them in a less uncomplimentary fashion as ‘invertebrates’, i.e. animals without backbones. He also came up with new and valid reasons for believing in the evolution of new species. But he then spoiled his case by endowing all animals with a special power to interact directly with their environment and acquire ever greater complexity or perfection, supposing for example that the length of a giraffe’s neck was the result of the animal constantly reaching up for food, or that the length of an anteater’s nose and loss of its teeth resulted from perpetual sniffing into anthills, and was inherited over many generations. In the absence of any good evidence for such an inheritance of acquired characteristics, the term ‘Lamarckian’ soon had pejorative connotations. The occasion to which Charles referred was possibly the first when Grant revealed his extreme views on transmutation in invertebrates, and metamorphoses in extinct fossils. At the end of 1827 Grant became the first Professor of Zoology and Comparative Anatomy at University College London,^* and his strongly Lamarckian approach was more widely disseminated. He held this post until his retirement in 1874, and though he was reported by Charles’s friend Frederick William Hope in 1834 to be ‘working away at the Mollusca & Infusoria publishing at a great rate’, in 1867 he was still teaching a defunct 1830s zoology in a frayed swallow-tail coat. Charles later noted that ‘he did nothing more in science – a fact which has always been inexplicable to me’. Grant’s excessively radical attitude, coupled with the disillusionment stemming from their falling out that March, may help to explain why their subsequent relations were never close, and there is no suggestion that Charles was ever subjected to the intimate approaches from Grant that may eventually have led to the nervous breakdown suffered by another of his students, John Coldstream.

Robert Darwin was far from pleased with Charles for giving up medicine, and told him angrily, and as Charles thought somewhat unjustly, ‘You care for nothing but shooting, dogs and rat-catching and you will be a disgrace to yourself and all your family.’²² After careful consideration, Robert decided that the only alternative for which there were several precedents in the Darwin and Wedgwood families would be for Charles to go up to Cambridge to take an ordinary Arts degree as the first step towards becoming an Anglican clergyman. In order to fulfil in due course the requirements for entry into the university, he had to brush up the Latin and Greek that he was supposed to have learnt at school, and a private tutor was therefore engaged for the last eight months of 1827. The period was not a very happy one for Charles, though he managed to escape to Uncle Josiah Wedgwood’s house at Maer Hall in Staffordshire, seven miles from Stoke-on-Trent, for at least the start of the shooting season, and made his first and only visit to France to collect his youngest Wedgwood cousins from Paris. But he did not record whether he also fitted in a visit to Cuvier’s famous Musée d’Histoire Naturelle.

Charles duly matriculated at Christ’s College, Cambridge, in January 1828. Here he quickly fell in with a new circle of young men from his own background and sharing his own tastes, one of whom described him at the time as ‘rather thick set in physical frame & of the most placid, unpretending & amiable nature’. Some years later, Charles advised his eldest son William at school:

You will surely find that the greatest pleasure in life is in being beloved; & this depends almost more on pleasant manners, than on being kind with grave & gruff manners. You are almost always kind & only want the more easily acquired external appearance. Depend upon it, that the only way to acquire pleasant manners is to try to please everybody you come near, your school-fellows, servants & everyone. Do, my own dear Boy, sometimes think over this, for you have plenty of sense & observation.²³

Charles’s own amiability and good relations with the rest of the world at every level were always among his most outstanding characteristics, and he had a true genius for friendship.

His new acquaintances included a number of schoolmates from Shrewsbury, and his cousin Hensleigh Wedgwood from Staffordshire, who had earlier seen a lot of Charles’s brother Erasmus in Cambridge. By far his closest friend to begin with was a cousin from the other side of the family, William Darwin Fox, the only son of Robert Darwin’s cousin Samuel Fox, who was then in his third year at Christ’s and due to become a parson in Cheshire. William Darwin Fox’s abiding passion, just as Charles’s had been in his childhood, was for the collection of exotic natural history specimens that filled every cubic inch of his rooms. He took great pleasure in shooting and riding, and kept two dogs named Fan and Sappho at Christ’s, about whose exploits, matching that of Charles’s Mr Dash at Shrewsbury, they had a regular correspondence. Fox encouraged Charles to take an interest in both art and music, and together they visited print shops and the Fitzwilliam Museum, and attended concerts of choral works in college chapels. Charles later joined a musical set headed by another good friend, John Maurice Herbert.²⁴ They went regularly to King’s College chapel to hear the anthem sung, and occasionally Charles hired the choristers to perform in his rooms. But as Herbert soon discovered, and as he himself freely admitted, Charles’s pleasure in listening was not in fact accompanied by a good musical ear. The interests of the group were wide-ranging, and extended at one time to the formation of the ‘Glutton’ or ‘Gourmet’ Club at which they dined when not eating in hall, and consumed a range of animals that did not usually appear on the menu. The club was finally brought to an end by an attempt to eat an old brown owl whose flavour was considered by all to have been ‘indescribable’. One wonders what the club would have made of some of the weird dishes later consumed in an experimental spirit by Charles on the Beagle.

The principal and most time-consuming occupation to which Charles was introduced by Fox was collecting and learning to identify beetles. Charles recalled later:

No pursuit at Cambridge was followed with nearly so much eagerness or gave me so much pleasure as collecting beetles. It was the mere passion for collecting, for I did not dissect them and rarely compared their characters with published descriptions, but got them named anyhow. I will give a proof of my zeal: one day, on tearing off some old bark, I saw two rare beetles and seized one in each hand; then I saw a third and new kind, which I could not bear to lose, so that I popped the one which I held in my right hand into my mouth. Alas it ejected some intensely acrid fluid, which burnt my tongue so that I was forced to spit the beetle out, which was lost, as well as the third one. I was very successful in collecting and invented two new methods; I employed a labourer to scrape during the winter, moss off old trees and place [it] in a large bag, and likewise to collect the rubbish at the bottom of the barges in which reeds are brought from the fens, and thus I got some very rare species. No poet ever felt more delight at seeing his first poem published than I did at seeing in Stephen’s Illustrations of British Insects the magic words, “captured by Charles Darwin, Esq.”²⁵

Public interest in natural history was at that time about to expand hugely, but few people pursued the new hobby with the passion, practical competence and competitiveness displayed by Fox and Charles. After breakfasting together daily, they scoured the fields and ditches closest to them at the ‘backs’ of the colleges, and the countryside further to the south of Cambridge, often accompanied by a bagman to carry their heavier equipment and their captures. When this man had learnt just what they were after, he would also collect for them when they were otherwise occupied. Returning to Charles’s rooms they would go through his reference books, from Lamarck to Stephens, to identify any rarities they had secured, and pin them out on a board for all to admire. On one such occasion after Charles had, after a ‘famous chace’ in the Fens, caught an especially rare beetle, he was pleased when Leonard Jenyns, vicar of Swaffham Bulbeck, and one of his principal collecting rivals in Cambridge, quickly came round to inspect it. Some years later, it was Jenyns who identified the fishes brought back by Charles in the Beagle.

When in June 1828 Fox went down from Cambridge, Charles felt himself ‘dying by inches, from not having any body to talk to about insects’. During the next three years, before the departure of the Beagle, he and Fox exchanged frequent letters, mainly concerned with entomology. They corresponded regularly during the voyage, and continued to keep closely in touch on family matters until Fox’s death in 1880. On sending Fox a copy of The Descent of Man in 1870, in which he had finally faced up to bringing Man into the picture, Charles added: ‘It is very delightful to me to hear that you, my very old friend, like my other books.’

In the summer of 1828 Charles and a number of friends went to Barmouth on the coast of Wales as a reading party that was intended to brush up their mathematics, but in the event became more concerned with entomology. Even the unfortunate Herbert, who was severely lame thanks to a deformed foot, was dragged to the tops of the hills in search of beetles, though Charles made up for it by helping to carry him down. The enthusiasm and thoroughness with which Charles pursued his beetles had already become a legend among his contemporaries.

At the beginning of the Michaelmas term, Charles moved into the rooms at Christ’s in which he lived for the next three years. A former occupant of the set had been the eighteenth-century theologian William Paley (1743–1805). Perhaps his influence still lingered there, for although Charles devoted very little of his time to theology, he said afterwards that he had greatly appreciated the clarity of Paley’s language and the strength of his logic, and regarded his books on Evidences of Christianity and Moral Philosophy as the only part of the academic course which had helped to educate his mind. However, he now had plenty else to do, for he kept a horse in Cambridge for riding, and having persuaded his father and sisters to provide the funds for a powerful double-barrelled gun with percussion caps, could practise aiming it at a lighted candle in his rooms. His beetles were never neglected, and towards the end of his period in Cambridge he took up once more the study of the inner workings of living cells by microscopy that he had begun in Edinburgh with Robert Grant. This was made possible by a gift from a generous and initially anonymous donor, who later turned out to be Herbert, of the latest compound microscope designed by Henry Coddington, a mathematics tutor at Trinity.

Unquestionably the most important event in Charles’s life while he was at Cambridge was his friendship with the Revd Professor John Stevens Henslow, of whom he had been told by his brother Erasmus, and to one of whose Friday evening soirées for scientifically inclined undergraduates and dons he was taken by Fox in 1828. Henslow had first been Professor of Mineralogy in Cambridge for five years, and then became Professor of Botany from 1827 to 1861. He and Adam Sedgwick, the Revd Professor of Geology and Senior Proctor in the University, had founded the Cambridge Philosophical Society in 1819. Together with William Whewell, polymath and later Master of Trinity, Charles Babbage, the designer of calculating engines, and George Peacock, mathematician and Professor of Astronomy, Sedgwick and Henslow were the leading figures in the development of scientific research and teaching in the university during the first half of the nineteenth century. Henslow’s wide-ranging lectures on botany, covering every aspect of the chemistry and biology of plants as well as the essential minimum of their taxonomic classification by Linnaeus, were attended annually by sixty or seventy undergraduates and several professors. The courses included field excursions, sometimes on foot or else in stagecoaches or on a barge drifting down the river to Ely, punctuated by talks on the variety of plants, insects, shells and fossils that had been collected. In the late spring there was always a trip to Gamlingay heath, twenty miles to the west of Cambridge, where rare plants and animals were to be found, and which ended with a convivial social gathering at a country inn. Charles signed up for these activities in 1829, 1830 and 1831. With at least some of Sedgwick’s lectures that he also attended in 1831, they constituted the only formal instruction in science that he received at Cambridge.

Speaking of the last two terms at the university after he had passed his Bachelor of Arts examination in January 1831, tenth in the list of candidates who did not seek honours, Charles wrote of Henslow in his Autobiography:

I took long walks with him on most days, so that I was called by some of the dons ‘the man who walks with Henslow’; and in the evening I was very often asked to join his family dinner. His knowledge was great in botany, entomology, chemistry, mineralogy, and geology. His strongest taste was to draw conclusions from long-continued minute observations. His judgement was excellent, and his whole mind well-balanced; but I do not suppose that anyone would say that he possessed much original genius.

It is true that by modern standards Charles would not be regarded as having had an orthodox or adequate scientific training. But by the standards of 1831, and remembering the contacts with Grant and the lectures that he had attended in Edinburgh, he was by then as well educated in natural history as any student in the country. And although he had not passed any exams in the subject, he had greatly impressed some of the most eminent scientists in Cambridge with his practical ability as a collector, and with the high quality and purposefulness of his enquiring mind. ‘What a fellow that Darwin is for asking questions,’ said Henslow.

At around the same time Charles read two books that ‘stirred up in me a burning zeal to add even the most humble contribution to the noble structure of Natural Science’. One was the classical account by the German naturalist, geophysicist, meteorologist and geographer Alexander von Humboldt (1769–1859) about his travels through the Brazilian rain forest to the Andes and beyond with the botanist Aimé Bonpland (1773–1858).²⁶ The second was the recent book by the astronomer and physicist John Herschel (1792–1871) on the study of natural science.²⁷ Charles insisted on inflicting long readings from Humboldt on his friends, and worked out plans for an expedition to the Canary Islands in July to inspect the volcanic cone of the Pico de Teide on Tenerife, whose summit had been closely inspected by Humboldt in 1799 on his way out to South America. Some of the requirements of his plan were tiresome to meet, such as taking ‘intensely stupid’ lessons in Spanish, though he was not to know how useful they would prove to have been when later on he was riding with gauchos across the pampas in Patagonia. A number of prospective participants were enlisted, but on enquiring about the sailing of passenger vessels to the Canaries, Charles found that his planning was already too late, for the boats were scheduled for departures only in June. The trip would therefore have to be postponed to 1832.

It was pointed out by Henslow that such an enterprise would require a basic knowledge of geology. He therefore advised Charles on the purchase in London of the instrument for the measurement of the inclination of rock beds known as a clinometer, and showed him how to use it. Soon Charles could boast from Shrewsbury that ‘I put all the tables in my bedroom at every conceivable angle & direction. I will venture to say I have measured them as accurately as any Geologist going could do.’²⁸

Most significantly of all for Charles’s training as a geologist, Henslow prevailed on Adam Sedgwick to take Charles with him for part of his usual field excursion during the summer vacation. Sedgwick was renowned as a field geologist, skilled at the recognition of regional patterns of strata from details that were strictly local, and in August he was planning to visit North Wales in continuation of a project to describe all the rocks in Great Britain below the Old Red Sandstone.^* The first nights of the trip were spent by Sedgwick with the Darwins at Shrewsbury, where he made a great impression, especially on Charles’s sister Susan, often teased by the accusation that ‘anything in coat and trousers from eight years to eighty was fair game to Susan’. Charles had been practising his geology in the neighbourhood, and later related the story of the important scientific lesson that he learnt on that occasion:

Whilst examining an old gravel-pit near Shrewsbury a labourer told me that he had found in it a large worn tropical Volute shell, such as may be seen on the chimney-pieces of cottages; and as he would not sell the shell I was convinced that he had really found it in the pit. I told Sedgwick of the fact, and he at once said (no doubt truly) that it must have been thrown away by someone into the pit; but then added, if really embedded there it would be the greatest misfortune to geology, as it would overthrow all that we know about the superficial deposits of the midland counties. These gravel-beds belonged in fact to the glacial period, and in after years I found in them broken arctic shells. But I was then utterly astonished at Sedgwick not being delighted at so wonderful a fact as a tropical shell being found near the surface in the middle of England. Nothing before had ever made me thoroughly realise, though I had read various scientific books, that science consists in grouping facts so that general laws or conclusions may be drawn from them.²⁹

Sedgwick had of course appreciated that the shell could not possibly be a genuine find in such a place. His scepticism taught Charles a valuable lesson, and brought home to him the importance of assembling plenty of mutually compatible observations to support any new scientific theory. Thereafter he would keep his mouth tightly shut until sufficient evidence had been accumulated.

Sedgwick’s aim was to follow the line of contact along the Vale of Clwyd between the Carboniferous Limestone cliffs and the Old Red Sandstone, shown in the geological map with ribbons crossing the Vale at several points, starting at Llangollen and finishing at Great Ormes Head on the coast.³⁰ At a quarry near Ruthin they found a possible outcrop of the Old Red, and north of Henllan there was red sand and earth, but Sedgwick was not sure that this established with certainty the nature of the underlying strata. Charles was therefore dispatched on a traverse of his own from St Asaph to Abergele via Betwys-yn-Rhos, crossing a substantial band of Old Red shown on the map. Finding in some places a few loose stones and some reddish soil, he noted: ‘It was in such points as these where the strata have been much disturbed, that I observed the greatest number of bits of Sandstone, but in no place could I find it in situ.’³¹ Near Abergele the soil was indeed ‘very red’, but this he attributed ‘entirely to the very ferruginous [rich in iron] seams in the rock itself, & not to the supposed sandstone beneath it’. That evening he told Sedgwick that there was no true Old Red to be seen, and to the end of his life could remember how pleased his teacher had been with this new evidence that the Vale of Clwyd did not have a complex structure as had been supposed, but was a simple trough-like syncline^* resulting from a stretching of the strata. Although his experience of geology in the field was thus limited to just one week, Charles had sat at the feet of a master, and had solved his first problem with conspicuous success.

Geological map of part of North Wales, redrawn by Secord¹⁵ after Greenough,³⁰ with Charles’s route from Llangollen to Penmaenmawr as a dotted line. In the second edition of Greenough’s map, published in 1839, the Old Red Sandstone had disappeared.

Among other sites of geological interest in the Vale were the famous caves in the limestone cliffs at Plas-yn-Cefn, above the River Elwy. Here the owner had excavated vertebrate fossils in the largest cave that included the tooth of a rhinoceros, and there were other bones in the mud. Charles’s imagination was fired by the prospect of making similar discoveries from past worlds in his projected trip to the Canaries, though his hopes were not in fact realised until his arrival in 1832 at the cliffs of Punta Alta in Patagonia. After a week, Charles and Sedgwick separated at Capel Curig in the neighbourhood of Bethesda, and Charles strode on across the central mountains of Wales, steering by map and compass, to join some Cambridge friends at Barmouth.

Reaching home at Shrewsbury on 29 August 1831 after two weeks of shooting with his Uncle Jos at Maer, ‘for at that time I should have thought myself mad to give up the first days of partridge shooting for geology or any other science’, Charles found the fateful letter from Henslow proposing that he should sail on the Beagle. The clock must next be turned back to explain its origin.