Joseph Hooker was one of the great botanists of the nineteenth century, long-time director of Kew Gardens, and close friend of Charles Darwin. Hooker was briefly employed by the BGS from February 1846 to October 1847; he was still in his late twenties and just at the very start of his illustrious career.
Some of Hooker's 'unregistered' slides were re-discovered in 2011. The slide labels had been directly inscribed onto the glass using a diamond tool, and a few were signed, 'J.D.H. 1846'. These initials stand for Joseph Dalton Hooker (1817–1911).
Hooker had made his name as an intrepid botanical explorer in the course of a circum-Antarctic voyage on HMS Erebus from 1839–1843.
At the Survey, his work dealt with the fossil plants of the Carboniferous Coal Measures, a task that he later confided to Darwin that he both loved and hated.
In those days, the Geological Survey of Great Britain was a young, vibrant organisation. Its roots had been established in 1835 under the directorship of Henry de la Beche (1796–1855), but the organisation only really took off in 1845, when a parliamentary act was passed to produce a comprehensive geological map of Great Britain.
That led to a spate of new hirings, and soon a small team of geologists, palaeontologists, and surveyors — mostly in their 20s and 30s — were out in the field, scrambling over Britain’s diverse rock formations.
One of these new employees was Hooker, who spent the summer of 1846 investigating the Bristol, Somerset and South Wales coalfields.
However, in the autumn of 1846, he informed Darwin that he was back at the Survey’s Museum of Economic Geology in Charing Cross, London. Here he was hard at work cataloguing specimens, almost certainly including those found in the ’unregistered’ fossil plant collection today.
The largest proportion of Hooker’s ‘unregistered’ collection comprises sections of Coal Measure plants from the Wolverhampton district and in the vicinity of Merthyr, South Wales.
These had been prepared from material that Hooker and his Geological Survey colleagues had obtained earlier that year.
The slides include beautiful examples of roots, trunks, branches, and ‘cones’ of the giant clubmoss tree, Lepidodendron — the iconic plant that dominated the Carboniferous coal swamps.
The names of donors inscribed on the slides show that Hooker’s work at the Survey relied heavily on the generosity of a huge number of amateur collectors — not unlike today.
Hooker published his findings in a three-part series that appeared as the first Memoir of the Geological Survey in 1848.
However, by the time that this weighty tome had come to press, he had already relinquished his employment, having embarked on his next botanical voyage of discovery, this time to India and the Himalayas.
Amongst the remaining slides that Hooker assembled in 1846 are specimens of fossil wood that he had collected in the course of his circum-Antarctic explorations onboard HMS Erebus.
Some of these are from the Kerguelen Islands, desolate volcanic rocks positioned at 49ºS in the wild southern extremities of the Indian Ocean, where Hooker spent three months in the spring of 1840.
The geology of the Kerguelan Islands is dominated by thick successions of Tertiary basalt flows, and Hooker wrote that, ‘throughout many of the lava-streams are found prostrate trunks of fossil trees of no mean growth’.
James Clark Ross (1800–1862), who famously led the expedition, added that one of these trees ‘exceeding seven feet in circumference was dug out and sent to England’. Perhaps this is one of the fossils now in the Survey’s collection?
Hooker informed Darwin that he had this specimen sectioned in December 1844. In the early twentieth century, Cambridge palaeobotanists, A C Seward and E A N Arber sectioned more of Hooker’s fossil wood specimens from the Kerguelen Islands, and identified them as conifers related to the modern-day monkey puzzle and cypress.
Many geologists now regard the Kerguelan Plateau as a kind of ‘Atlantis’, which was covered by subtropical vegetation throughout much of the Tertiary, before largely sinking below the waves.
From the desolation of the Kerguelan Islands, Hooker sailed onto Tasmania in south-east Australia, arriving in August 1840. There, local people took him to see ‘vast quantities of silicified wood’ scattered over the Macquarie Plains.
Amongst these was a massive fossil tree buried upright in basalt lava flows of Tertiary age, measuring some three feet in diameter and nine feet high. With some difficulty, this specimen of ‘most beautiful agate’ was shipped back to England, where it was showcased at the Great Exhibition of 1851, before going to its permanent home at the British Museum (Natural History) in London — now simply the Natural History Museum.
Fifty years later, Arber named the specimen, Cupressinoxylon hookeri in honour of its discoverer.
In Hooker’s ‘unregistered’ collection at the Geological Survey, there are fifteen sections of Tasmanian fossil wood, mostly labeled Van Diemen’s Land (the official name of the island until 1856). Exactly how they relate to the giant tree, if at all, is unknown.
Fossils from a slightly earlier round-the-world voyage are also stored with Hooker’s specimens at the Geological Survey. These include at least two sections of fossil wood obtained by Charles Darwin in the course of his famous voyage of the HMS Beagle, from 1831–1836.
In December 1834, Darwin explored the northern part of Chiloe Island, Chile, under conditions of persistent rain. Far from enamored by the place, he had written that, ‘Chiloe, from its climate is a miserable hole’.
However, in the course of his visit, Darwin encountered ‘many fragments of black lignite and silicified and pyritous wood, often embedded close together’, probably from Tertiary deposits along the coast.
He shipped these specimens back to Robert Brown (1773–1858), Keeper of the Botany Department at the British Museum (Natural History), who had them cut and ground into thin sections in 1837.
Darwin’s correspondence shows that he and Hooker exchanged fossil wood slides in 1844, and in this way, some of Darwin’s sections seem to have found their way into the Geological Survey’s collection. One is labelled ‘Chiloe, C. Darwin Esq’.
While rediscovering ‘lost’ fossils from Darwin’s voyage on HMS Beagle is hugely exciting, there are other specimens in Hooker’s ‘unregistered’ collection that are arguably of greater scientific significance.
These are associated with William Nicol (1771–1851), the pioneer of petrography, who invented the polarizing microscope and produced the first-ever thin sections — some of which are in the Geological Survey’s collection.
The impetus for Nicol’s twin breakthrough was the discovery, in 1826, of a gigantic Carboniferous fossil tree in Craigleith Quarry on the outskirts of Edinburgh where he lived. Over the next three years, Nicol experimented with samples of this fossil, in collaboration with lapidary, George Sanderson.
Eventually, they created the first translucent sections by attaching ground slices of fossil wood to glass plates using Canada balsam — laying the foundations of petrography.
However, the numerous thin sections from this era preserved in the ‘unregistered’ collection of the Geological Survey, do not all appear to have originated directly with Nicol, but instead shed light on a rather murky episode in the history of science.
One of Nicol’s closest friends and supporters was Henry Witham (1779–1844), a wealthy naturalist from County Durham. Recognising the potential of the thin section technique to revolutionise palaeobotany, Witham encouraged Nicol to produce many more sections and used his contacts to source fossil wood samples from across northern Britain.
However, the collaborative relationship seems to have turned sour when, in 1831, Witham published a groundbreaking book based on Nicol’s sections, entitled Fossil Vegetables.
Although Witham fully acknowledged his debt to Nicol, the latter had evidently expected co-authorship. Worse was to come, however, because with Nicol now unwilling to collaborate further, Witham continued to work directly with Sanderson to study further fossils, resulting in a second expanded edition of his book in 1833.
As an indication of the degree of bad feeling that had developed between the two men, this edition made no reference to Nicol at all.
At least thirty thin sections from Witham’s former museum at Lartington Hall, County Durham are preserved in Geological Survey’s ‘unregistered’ collection. How they found their way from County Durham to London is unclear, but as Witham died in 1844, the likelihood is that the geological contents of his museum were donated to the Survey about the time of Hooker’s arrival as botanist in 1846.
Reflecting the split between Nicol and Witham, the sections made for the first edition of Fossil Vegetables are labelled in Nicol’s handwriting while those prepared for the second edition are engraved by Witham.
The specimens are mostly of lower Carboniferous trees from several sites across Scotland and its borders, but also include Jurassic specimens from the Yorkshire coast, and Tertiary angiosperm trunks from as far afield as the East China Sea.
Witham’s book, Fossil Vegetables, described his thin section technique in sufficient detail that anyone with basic know-how could replicate the process; Nicol was especially annoyed by this. Read more about this in Double-crossed Nicol.
As a result, by the mid-1830s, a small handful of professional slide-makers, mostly based in London, had set up business to supply the growing demand from gentleman collectors for geological thin sections.
Slides prepared by three of the best known of these early professionals are represented in Hooker’s ‘unregistered’ collection, and combine science with some extraordinary artistry.
One of these slide-makers was William Hill Darker (1811–1863), who worked out of Lambeth, London, in the late 1830s. Many of his sections were evidently made for coal geologist, Edward Binney (1812–1882), and the localities of the fossils, in and around Manchester, suggest that they date from the early 1840s.
The other slide-makers were Charles M Topping and Cornelius Poulton, and date from a similar period.
The truly remarkable thing about all these slides is the way they illustrate the ‘global reach’ of British science in the early nineteenth century; fossil woods were sourced from Antigua, Australia, Egypt, India, Jamaica and the Far East, as well as many classic English localities including the Isle of Portland, Dorset.
Intriguingly, many of these slides give the name of the donor as ‘Miss Henslow’. That suggests some sort of connection with the Rev. John Stevens Henslow (1796–1861), Darwin’s mentor at Cambridge and a keen collector of fossil woods.
In 1847, Hooker became engaged to Henslow’s oldest daughter, just a few months after he assembled the Geological Survey’s slide collection. It seems likely therefore that many of the specimens found in the ‘unregistered’ collection today originated from the Rev. Henslow’s personal cabinet.
Others seem to have been donated by a motley crew of explorers, missionaries and administrators from across the British Empire.
Despite the passing of 165 years, the origin of Hooker’s ‘unregistered’ collection is slowly becoming apparent. However, far less clear is how it came to be ‘lost’.
The answer to that question may simply be a case of bad timing. As already noted, the Geological Survey’s formal register of acquisitions only commenced in 1848, two years after Hooker had assembled his collection; however, by that time, he was off exploring the wilds of the Himalayas, and unavailable to assist with cataloguing his thin section collection.
When he returned in 1851, the collection was in the process of being moved to a new home at the Museum of Practical Geology in Jermyn Street, Piccadilly, London; from there it travelled to the Geological Museum in South Kensington in 1935, and 50 years later, to its current home in Keyworth.
With each move, the origin and significance of the collection became ever more obscure. However, that trend may now be set to reverse because the entire collection has been accessioned, photographed, and will shortly be made available online.
It is hoped that this, in turn, will stimulate more research, shedding light on the early history of palaeobotany, and affording these beautiful slides, the attention that they have been denied for so long.
This is part of an edited transcript of the following article:
FALCON-LANG, H J. 2012. Fossil 'treasure trove' found in British Geological Survey vaults. Geology Today 28 (1), 32–36. Reprinted by permission of Wiley-Blackwell