In Shropshire, we have evidence from eleven of the thirteen recognised geological periods here, more than anywhere else in the world, and the county hosted many of the earliest explorations into geology as a science.
Growing up in Shrewsbury, the young Darwin was an avid collector, and fascinated by pebbles – he wanted to know something about every pebble in front of the hall door.
Bellstone, Shrewsbury
As a teenager he was shown the Bellstone, a granite glacial erratic in Shrewsbury town centre and was told there were no rocks of this sort nearer than Cumbria – at that time, a fascinating mystery.
Darwin’s first exposure to the formal study of geology was at Edinburgh University, where he studied medicine. He attended lectures on geology, but says in his Autobiography “The sole effect they produced on me was the determination never as long as I lived to read a book on geology”.
Fortunately, his removal to Cambridge University, where he studied theology, led to a friendship with the mineralogist Reverend Professor John Stevens Henslow who “influenced my career more than any other!” (CD) and encouraged him to study geology when he had to stay up for 2 terms after his final exams to fulfil the University residence requirement. Henslow also introduced him to Professor of Geology Adam Sedgwick.
By now “mad about geology”, Darwin ordered a compass clinometer, made to a modified design by Henslow – an essential tool for geologists. He re-arranged and surveyed his bedroom furniture for practice, then took himself off to explore the geology of Shropshire. (July-August 1831), writing:
I suspect the first expedition I take, clinometer and hammer in hand, will send me back very little wiser and a good deal more puzzled than when I started
First he “coloured a map of parts around Shrewsbury” (CD) with orange shading indicating New Red Sandstone but making no allowance for drift. He then ventured to Llanymynech. He would already have known there was well-bedded and jointed limestone there affording three-dimensional exposures, good for practicing geological mapping. Of course, it was a working quarry then and the exposures he studied are lost.
Darwin’s geological sketch map of Shrewsbury (Cambridge University Library)
His notes of the trip are “immature” and his terminology confusing, for example, he used ‘direction’ and ‘inclination’ rather than the standard geological ‘strike’ and ‘dip’ and was imprecise about naming rocks – it was very much the work of a neophyte struggling on his own, but there is evidence that Sedgwick made use of Darwin’s notes in his seminal research.
Henslow persuaded Sedgwick to allow the young Darwin to accompany him on a fieldtrip to North Wales, which shows Sedgwick as well as Henslow must have had belief in Darwin’s potential. Before they set off, Sedgwick stayed at Mount House (The Darwin's family home in Shrewsbury) and they spent a couple of days geologising around Shrewsbury – possibly even knocking a sample off the Bellstone (now in the Sedgwick Museum, Cambridge).
Darwin’s notes, which can be compared with Sedgwick’s, show a rapid development of geological ideas and skills, and towards the end of the trip, when Darwin was once again geologising on his own, he is described as displaying ‘a considerable geological expertise’ as ‘a highly skilled and rapidly maturing geological observer’.
Sketch of Darwin c.1838
He put all this into practice when he left shortly after on the Beagle voyage, where his own observations of glacial processes in South America brought to mind his earlier reading about the action of icebergs in transporting boulders and his musings on the Bellstone.
Once back in Shropshire he returned to the local geology and interpreted the glacial drift deposits (moraine) in Shropshire and the high-level erratics in Snowdonia as caused by submergence and floating icebergs, followed by an uplift of the land. This uniformitarian theory opposed the catastrophist thinking of William Buckland, who regarded the drift deposits and the glacial features seen in North Wales as relics of the biblical flood.
By concluding that both terrestrial glaciation and submergence with associated icebergs had occurred Darwin ‘set the glaciological agenda on a false trail for several decades’. He was right about the ice though. His “elevation theory”, first developed in Scotland and then applied to the area from Caernarfon to Staffordshire set the scene for two decades of glacial geology, and despite the fact he conducted no further geological fieldwork in the area he continued to pursue his interest in glaciation with various correspondents and inspire them to further research.
Blog written by Dr Cath Price, Engagement Officer, Shropshire Wildlife Trust, as part of the Shrewsbury Darwin Festival 2021. This Annual festival celebrates Charles Darwin's links with Shrewsbury. Find out more here.
