HE ORIGIN OF DARWIN AS A NATURALIST
Darwin concluded The Origin of Species with this magnificent paragraph;
It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us. These laws, taken in the largest sense, being Growth with Reproduction; inheritance which is almost implied by reproduction; Variability from the indirect and direct action of the external conditions of life, and from use and disuse; a Ratio of Increase so high as to lead to a Struggle for Life, and as a consequence to Natural Selection, entailing Divergence of Character and the Extinction of less-improved forms. Thus, from the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of the higher animals, directly follows. There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.
This makes me think of the narrow country roads in Shropshire, which were sunken by cart traffic over hundreds of years leaving high banks on either side. These banks became entangled with plants (hawthorn, brambles, hazel, campanula, primroses, snowdrops etc.) and colonised by various animals (insects, butterflies, lizards, rabbits, polecats etc) and host to birds.
The entangled bank was an integrated ecological web.
As Darwin rode round these lanes on his horse Dobbin, whether en route to his girlfriend, Fanny, or to shoot, he would have passed many entangled banks and observed the wildlife. From so small a beginning of a teenage horse rider and amateur naturalist came the most profound of scientific theories.
The Skills Darwin learnt before sailing on the Beagle
Outdoor skills from hunting and shooting and exploring.
Navigation, use of maps
Travelling through rough country, which still can be dangerous.
A wide range of naturalists skills, observation of plants and animals, habitats, specimen collection and preservation.
A good basic geology.
This is why when he boarded the Beagle in December 1831 he was one of the most proficient young naturalists of his day.
The influences on Darwin. (1809-1882)
He was born at The Mount on 12 th February 1809
and went to Shrewsbury School under Dr Butlet but was taught little but Greek and Latin and no science
His father was a doctor with a good knowledge of science (and less on dietetics) and his grandfather, Erasmus, even more so. So from home he learnt much.
His older brother, Erasmus, built a very good chemistry lab in a shed
He collected eggs etc from an early age.
He was keen on hunting thus observed the behaviour of foxes and birds.
From his late teens he collected beetles by the thousand!
1825-27. He studied at Edinburgh for medicine and also learnt some geology and also marine invertebrates from Robert Grant
1827-1831. He studied theology and philosophy at Christ’s College, Cambridge and intended to get ordained. There was no official science teaching but John Henslow gave unofficial classes and field trips.
1824-30 He did much naturalising around Shropshire and visited North Wales most years either to Snowdonia itself or to Barmouth. He climbed most of the mountains
He went on great hikes and observed all he saw on the wildlife and a little on the rocks. His favourites were beetles, but also fungi and birds (which he shot to collect specimens)
His favourite mountain was Cadair Idris and he shot birds for specimens at Bird Rock
He explored the rugged Rhinogau with epic hikes and explored the Mawddach estuary
He stayed at Barmouth supposedly being tutored in the binomial theorem but preferred other things!
He left Cambridge in June 1831 and as he was planning an expedition to Tenerife he did geology around Shrewsbury and in July 1831 tried to make a geological map and visited the limestone hill of Llanymynech.
The last of the four photos is from Nesscliff where he studied a Permo-Trias outcrop. The view is of the volcanic Breidden Hills and to the left is Long Mountain which is capped by Old red Sandstone. Darwin and Sedgwick got within a mile of an exposure but turned back, thus making Sedgwick miss a vital exposure.
The Sedgwick–Darwin Tour 3 to 20 August 1831
To the West of Shrewsbury 3-4 August
Shrewsbury to Denbigh, 5 to 7 August
Alone to Conwy, 8 to 9 August
Conwy to Bethesda, 10 to 11 August
To Anglesey and Dublin? 12 to 20 August
Separate Ways, 20 August
Caernarvon to Barmouth via Cwm Idwal 20-24th August
This map shows the route
They both had a copy of Greenhough’s map. They new that the Orange rock in the south was Old Red sandstone (later Devonian) and it was younger than the older strata (later Cambrian, Ordovician and Silurian) which he wanted to study. The aim was to find the ORS and then older rocks below it. Murchison who went to South Wales was guided to the contact by Rev Thomas Lewis and sorted it all out. Sedgwick’s aim was to follow the arc of ORS (orange rocks) along the North Wales coast and Llangollen and then find the older rocks below. That determined Sedgwick’s route and his pupil Darwin just tagged along. as it turned out Sedgwick just missed ORS at Long mountain while at Shrewsbury and then discovered there was no ORS in North Wales so he lost his stratigraphic marker! So when he started on 21st August 1831 on his own, he bagan in Llanberis which was not the best place to start, but that is another story.
They travelled by gig with a driver. this picture is of one of Dr Robert Darwin’s patients -Mad Jack Mytton who though affluent died in a debtors jail.
In August 1831 Adam Sedgwick (geology professor at Cambridge) came to Shrewsbury after looking at strata in Dudley
and after a few days of geologising near the town they travelled to North Wales by gig (2 –wheeled carriage pulled by a horse) trying to work out what strata there were below the Devonian.Their first stop was up Castell Dinas Bran (silurian) and then to the Carboniferous Limestone of the Eglwsyeg cliffs. There is a fault between the two hills and no Devonian.
Next day they drove to Ruthin and looked first at Silurian strata by Vallee Crucis abbey, which shows the difference between bedding and cleavage.
On to the top of the Horseshoe pass (my first big hill on a cycle) looking over to the grey limestone cliffs. The road was built in the 1810s to service the slate quarry
Glancing over to Snowdonia behind the sheep they descended to Dafarn Dowarch, then made out of turf. Sedgwick stayed here in the 1840s.
Past some limestone then descended to the complex Clywd basin of the Vale of Clwyd going past more Transition/silurian slate. This windy road is Nant y Garth, which I once cycled up in a thunderstorm doing field work for this. That was memorable.
Darwin walked the last 6 miles to Ruthin where they stayed at the Castle Hotel.
At Lanfwrog to the west Darwin found some red sandstone lying topographically below Carboniferous Limestone 50 yards away. In fact, it was New Red Sandstone, not Old Red/Devonian which had been downthrown to the east. Alas there was no basin analysis to help them!!
And then down some lovely lanes which would have been muddy! they visited the Ogof caves and found some rhino fossils – teeth.
They took the road west of St Asaph and near Glascoed Darwin was dropped off to do a 20 mile traverse and Sedgwick carried straight on to Conwy.
Darwin’s brief was to find ORS below the Carboniferous and above the Silurian/Transition. The second photo is taken a few miles west looking north towards Abergele. The hills are Carb limestone and and the foreground is Silurian. Darwin must have been miffed not to find any ORS.
He stayed at Abergelle and the next day walked to the Ormes and Llandudno chasing the non-existent ORS
He left the Great Orme behind and crossed the brand-new bridge to Conwy and met Sedgwick near the castle.
The next day, after Darwinstopped Sedgwick arguing with a waiter, they went up the Conwy valley to Cannovium and over the 2100ft Tal y Fan and dropped down to Aber for the night. They visited Aber Falls the next day and then went to the Bethesda Slate Quarries
Here is the major problem I encountered in this study. Darwin’s notes on Cwm Idwal – 5 miles from the quarries – follw straight on from his notes on Bethesda. further in his Autobiography Darwn states he went round Cwm Idwal with Sedgwick. HE DID NOT. This is countered by the letters between D and S in September 1831 when Darwin told Sedgwick what he saw on his own and then Sedgwick corrected him after visiting Cwm Idwal a fortnight later.
Instead the went across Anglesey, as Sedgwick had Henslow’s wonderful 1822 geological map to guide him, but the ORS was still elusive and this supposed outcrop of ORS later turned out to be Ordovician. Later at Cape Verde Darwin described some recent conglomerates by the shore as hard as this. I can assure that the rock is very painful to hit with a hammer.
And so the crossed the Menai Straits and shot down the newish London-Holyhead road, which had just been replaced by a dual carriageway when I visited there.
From Holyhead they took a steam-packet to Dublin for the weekend as Sedgwick wished to meet some geologists. On their return they went to look at the precambrian rocks at north Stack and then went across Anglesey with Henslow to guide them.
They found what Henslow’s incredibly hard ORS on which I nearly broke my arm. And so to the old Copper Mine at Parys Mountain. It dates back to the Bronze Age and I think it is still being mined
And so they arrived at Caernarfon, when Darwin wanted to go home for the start of the shooting season. Sedgwick went to Llanberis and started in ernest and found it hard.
On his own from Caernarfon to Barmouth 20th to 24th August
Darwin left Sedgwick at Caernarfon and then visited Cwm Idwal on his own. He reckoned that the Devil’s Kitchen was a volcanic plug, but Sedgwick put him right a little later, explaining it was a syncline.
A sketch to show what Darwin thought about Cwm Idwal and how Sedgwick corrected him.
He found the geology difficult as I did when I tried to do my undergraduate mapping there. (I gave up and mapped a layered intrusion in Northern Canada instead!!). He was oblivious of any glacial features. He must have found some predators – sundew.
Two views of Cwm Idwal
From Cwm Idwal it was 6 miles to Plas y Brenin, the coach inn at Capel Curig, where he spent two nights. The next day he climbed Moel Siabod and made more notes . After that he walked to Dolwyddelan and over the moors to Ffestiniog for the night. The next day he cross the Rhinogau by the the Bwlch Drws Ardudwy
An early morning view from Plas Y Brenin
In his autobiography Darwin claimed to follow a compass bearing to Barmouth. I do not believe him! First, the route would be an utter killerwading through boulders and 3 foot heather. Secondly his geological notes describe the localities visited and I mark these on the sketchmap.
Moel Siabod and the moorland south of Dolwyddelan
My key outcrop to determine his route was Carreg y Fran, which I located. Darwin said the rocks at the base of the cliff were conglomerate. They were in fact agglomerate.
From there he cross the remote and rugged Rhinogau and made his way to Barmouth.
After a few days at Barmouth Darwin returned home for the shooting season. Instead he accepted an invitation to travel on the Beagle
Here is Topper (1992-1994) my faithful field assistant, navigator and mountain climber.
He took a stagecoach back to Shrewsbury and found a letter inviting him to join the Beagle!
In the summers of 1837 and 1838 he spent a few weeks while staying with his father in Shrewsbury looking at glacial deposits (c18000 years old around the town and by the field centre)
At this time he was very ill and only walked short distances.
In June 1842 he felt better and wrote the first half of a draft on evolution and went to Snowdonia and went home to finish it. It as not published.
Darwin spent two weeks in Snowdonia, staying at Plas y Brennin and other inns.
He looked for evidence of glaciation especially in Cwm Idwal and was convinced that Snowdonia used to have glaciers. He could only walk five kilometres.
But this will be my next installment
CHARLES DARWIN AND THE HISTORY OF GEOLOGY, 1831 AND 1842
Along with many earlier visits to Snowdonia, the mountainous region of North Wales, in the 1820s to study natural history and to “climb every mountain”,
Darwin made two important visits to study the geology. In 1831 he spent nearly four weeks studying the geology of Shropshire and North Wales, mostly under the tutelage of Adam Sedgwick of Cambridge and then in 1842 to see whether there had been “former glaciations2 in Snowdonia. In 1831 he was a “learner” and made no contribution to geology, but his work on glaciations was highly significant.
My purpose here is to put Darwin’s two visits into the whole context of geology as a developing science. I give it in note form as a developing historical theme.
- 1660-1700. Earliest geology beginning with Nils Steno in Italy. Little grasp of an ancient earth
- 1690s E Lhwyd (born near Oswestry – 20 miles from Shrewsbury) and John Ray (the English Linnaeus) noted the boulders in Nant Peris a valley below Snowdon. As there were lots of boulders and only one or two fell down in a lifetime, they suggested that the earth must be much older that the biblical 6000 years. These were in fact glacial erratic transported there by glaciers.
- 1700- 1800 more evidence for an ancient earth and beginnings of working out the order of strata
- 1788 Rev John Michell, prof of geology at Cambridge worked out an order of strata;
Chalk Upper Cretaceous 120ft
Golt (Gault Lower Cretaceous 50ft
Sand of Bedford Lower Greensand – lwr Cret 10-20ft
Northamptan andPortland lime (Jurassic) 100ft
Lyas strata (Lias –Lower Jurassic) 100ft
Sand of Newark (Triassic) 30ft
Sherwood Forest pebbles and gravel Permo-triassic sandstones 50ft
Very fine white sand uncertain
Roche Abbey and Brotherton Lime (Permian Magnesium lst) 100ft
Coal Strata of Yorkshire Upper Carboniferous
This gives a good summary of strata from Upper Carboniferous to Upper Cretaceous
- Smith developed this with use of fossils and then Geology map of England and Wales 1815.
6 Cuvier worked on Cretaceous strata around Paris
- By 1820s strata reasonably well-known down to Old Red Sandstone/ Devonian. What lay below was totally unknown and refered to Killas. This was classically put in The Outline of the Geology of England and Wales by Conybeare and Phillips (1822)
Below are a series of geological columns and the final development for today is the right hand column. What is crystal clear is that the order has not changed since Michell made his preliminary one in 1788. After the publication in 1822 there was an immense amount of geological fieldwork all over Europe but only the British work concern us.
SELECTED CLASSIFICATIONS OF ROCK STRATA
1799, 1812, 1815
|CONYBEARE and PHILLIPS
|DE LA BECHE
Red and Dunstone
Killas and Slate
|SUPERIOR ORDER or TERTIARY
Upper Marine(Freshwater: London Clay, Plastic Clay)SUPERMEDIAL ORDER
Coral Rag, Oxford
New Red SandstoneMagnesian Limestone
Old Red SandstoneSUBMEDIAL ORDERTransition LimestoneSerpentine
Clay SlateINFERIOR ORDER
Erratic Block Gr.
Red Sandst. Gr.
Old Red Sandst
CretaceousWealdonOolite or JuraLias
Trias or New Red
Mountain LsOld Red Standst.
1830s. After the publication in 1822 there was an immense amount of geological fieldwork all over Europe but only the British work concern us. By 1830 British geologists had felt clear on the geology from the Old Red Sandstone to the top of the Cretaceous, but what lay above and below was still to be discovered. Lyell was instrumental in bringing order to the Tertiary, but in 1830 Sedgwick and Murchison decided to tackle what lay below the ORS in Wales, in preparation for a second volume continuing Coneybeare and Phillip’s work. They had described what lay below the ORS as SUBMEDIAL ORDER; Transition Limestone, Serpentine, Sienite, Greywacke and Clay Slate, indicating that it was scarcely elucidated. All this later came to be termed Cambrian, Ordovician and Silurian, but in 1830 it was simply unknown strata.
(Shrewsbury is just north of the Long Mynd on the map, and Cwm Idwal is slighty above the letter “N” of Snowdonia)
The map above is a sketch map fo the geology of North Wales marking all strata older than the Devonian, i.e. all the shaded area on the map. In 1830 the weather was so bad that neither geologist went to Wales, but both went in the Summer of 1831. Murchison went to Southern Wales about 25 miles southwest of the Longmynd and was guided to an excellent downward succession from ORS to what was to be called Silurian by the Rev Thomas Lewis. Sedgwick went to Northern Wales and his aim was to find the ORS (marked on geological maps as lying below Carboniferous Limestone from Llangollen to Conway. When he found the ORS he hoped to find it going down conformably into Killas/grauwacke (now Silurian). This did not happen and he and Darwin concluded that there was no ORS from Llangollen to Conway, thus frustrating his intentions. Ironically at over 300 metres on top of the Long Mountain between Welshpool and Shrewsbury , there is a capping of ORS/Devonian strata but Sedgwick and Darwin did not go up the steep hill in their gig, thus missing the solution to the puzzle by two miles!
In early August Sedgwick and Darwin left Shrewsbury for North Wales to look at the base of the Carboniferous Limestone hoping to find first ORS and then “Silurian” below it. They failed as there was no ORS. After that they went round Anglesea and found that no more helpful, though they found some ORS identified by Henslow in 1822, though some of that was mis-identified and turned out to be far older. On 20th August Darwin left Sedgwick to go home via Cwm Idwal and Barmouth. Sedgwick started working on strata by Llanberis, but had no stratigraphic markers or fossils to guide him. After a few years he managed to make sense of the geology. Sedgwick called all these Cambrian and Murchison called southern Wales strata Silurian. It took another 50 years to sort them out properly into Cambrian Ordovician and Silurian.
After leaving Sedgwick at Caernarfon, he took a coach to Cwm Idwal, not knowing anything about the geology, except that it was older than the ORS. He had no geological guides to help him, so simply made notes. Cwm Idwal is a glacial cirque carved out of Ordovician Volcanics. Darwin gave brief descriptions regarding most as “altered slate” with some resembling basalt.
He also note volcanic rocks at Devil’s Kitchen which he considered the Volcanic rocks at Devils Kitchen to be “Basalt protruded out of the slate” as an “inverted cone”. In fact, they were laid flat and then gently folded into a syncline, as Sedgwick pointed out to Darwin in a later letter after .
1842 Glacier visit
In 1842 Darwin returned to Snowdonia, having travelled round the world in the Beagle. His purpose was to see whether the Glacial Theories of Agassiz and Buckland were correct. In 1838 he had been to Glen Roy and in 1838 and 1839 had looked at the gravels around Shrewsbury and concluded that “glaciers” has some influence. Initially he was wary of Agassiz’s ideas of a continental ice age and after Buckland visited Snowdonia in October 1842, when he demonstrated glaciations, Darwin went to Snowdonia for 10days in June 1842. (In fact he had half written his first manuscript on Natural Selection before he went and finished it on return.)
He confirmed the terrestrial glaciations in Snowdonia and confirmed Buckland’s identification of glacial troughs. The highlight was his visit to Cwm Idwal where he identified the remains of an icefall by Ogwen cottage, ice-scoured rocks and moraines. Most interesting are two boulders he described, now known as Darwin’s boulders. After visiting Moel Tryfan, which he realised was sea-ice he returned to Nant Peris near Llanberis and made more observations.
Darwin had confirmed that these deep valleys were not formed by rivers………
Darwin at Llanymynech; British Journal for the History of Science, 1996, Vol 29, pp469-78
Darwin’s Dog-leg ; Archives of the History of Natural History, 1998, Vol 25, p59-73
I coloured a map ; Archives of the History of Natural History, 2000, Vol 27,p69-79
Charles Darwin’s 1831 notes of Shropshire,Archives of the History of Natural History 2002,Vol 29 , p 27-9; co-authored with Prof.S.Herbert (University of Maryland)
Darwin’s Welsh Geology, 1831, Endeavour Spring 2001, 25, p33-37
Darwin, Buckland and the Welsh Ice Age, 1837 – 1842, accepted for publication in Proceedings of the Geological Association 2012
Sandra Herbert; Charles Darwin;geologist 2005
A stormy sunset from Plas y Brenin looking to Snowdon – Crib goch peeping through the clouds