‘The last time I was ever strong enough to climb mountains’

1836-1842: Shrewsbury, Cambridge, London Back from the Beagle and Darwin began writing up his notes and publishing papers and in July 1937, ‘I opened my first note-book for facts in relation to the Origin of Species, about which I had long reflected, and never ceased working for the next twenty years.’ He wasn’t always desk bound, making excursions to Glen Roy in the Highlands and back to Cwm Idwal.

Both trips show the excitement of discovery – we’re so familiar with the idea of glaciation that we can’t imagine looking at Cwm Idwal and not knowing how it was formed. It wasn’t until this second visit in 1842 that Darwin worked it out, reminiscing about his first outing: ‘ We spent many hours in Cwm Idwal, examining all the rocks with extreme care, as Sedgwick was anxious to find fossils in them; but neither of us saw a trace of the wonderful glacial phenomena all around us; we did not notice the plainly scored rocks, the perched boulders, the lateral and terminal moraines. Yet these phenomena are so conspicuous that, as I declared in a paper published many years afterwards ...a house burnt down by fire did not tell its story more plainly than did this valley.’

And Glen Roy proves the path to scientific truth is littered with dead ends. Darwin published a paper about its parallel roads (terraces along the hillside) claiming they were formed by sea action. The idea was refuted by geologist Louis Agassiz who said they’d been made by glacial lakes, and Darwin eventually came to think of the theory as ‘one long gigantic blunder’.

His close observation of the world extended to romance too, as he debated the pros of marrying (‘Constant companion & friend in old age who will feel interested in one – object to be beloved & played with – better than a dog anyhow’) and not marrying (‘Freedom to go where one liked... Conversation of clever men at clubs– Not forced to visit relatives & to bend in every trifle’) before wedding his cousin Emma Wedgwood in January 1839.

Darwin was soon beset by ill-health and later remembered the 1842 excursion to Snowdonia and his work at Cwm Dwythwch on Moel Eilio, at Llyn Idwal and the ‘vomitory’ of the rushing

Ogwen Falls, as ‘the last time I was ever strong enough to climb mountains or to take long walks’. WALK HERE: Find routes at Cwm Idwal and Moel Eilio at www.lfto.com/bonusroutes and for Glen Roy at www. walkhighlands.co.uk/fortwilliam/ parallel-roads.shtml.