Fossils, Finches and Fuegians: Charles Darwin’s Adventures and Discoveries on the Beagle. Richard Keynes
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