In June 1842 Charles Darwin undertook his last geological field trip. He was at his father’s house, The Mount in Shrewsbury, that month and after a winter of sickness, he felt somewhat better. Thus, he went in his gig to Snowdonia to assess whether Buckland was correct in identifying proof of a former Ice Age. In October 1841 William Buckland travelled to Wales with Thomas Sopwith (his grandson designed the Sopwith Camel, a WW1 fighter plane) to see whether Agassiz could be right about a former Ice Age. In a few days of horrendous Welsh weather Buckland identified all the main glacial troughs
Buckland dressed for Welsh Glaciers by Thomas Sopwith
View from top of Y Garn 3104ft showing the Llugwy trough leading to Capel Curig, Llyn Idwal, a morainic lake.
To the left is Nant Francon, viewed below – with embellishments.
In 1831 de la Beche painted this watercolour to show that little rivers could not produce big valleys. He was right, but ideas of glaciation were a few years ahead.
This map shows the routes of both Buckland and Darwin in 1841-2 with some further details
This map shows the locality of Cwm Idwal with the lake/llyn in the centre.
Darwin spent a few days in Capel Curig and then several around Cwm Idwal before moving on to Moel Tryfan and then Llanberis and Snowdon.
Most iconic are the boulders he found in Cwm Idwal dubbed the Darwin Boulders. Here is the partial transcription of his 1842 notes, which are often scarcely legible
60- 80 yards west of exit of river – a gigantic boulder
broken into 4 tabular surfaces thus rest on their narrow edges
upright. the two lower ones have fallen over + rest on
neighbouring grt boulder _ the two upright plates stand
transversely on gentle slope in which they rest _ the fragment and
so far a part this xxxxx xxxx must have been
thrown with force where it now stands, but not rolled
from neighbouring precipice otherwise plates have been thrown
over . _ action of ice. fallen though . _ example xxxx
stronger . =
First, the boulders lie to the EAST of the “exit of river” and not the WEST, which confuses all. It is alway great to confuse students!!
He sees the 4 (angular ) bits as the original boulder which fell through the glacier and landed on another which shows a few marks of being water-worn.
At that time Buckland and Darwin only noted AN Ice Age and not a succession of them as became apparent later. This in itself was a great breakthrough
The boulders with Twll Du/ Devils Kitchen behind which he described in 1831
Boulders with Pne yr Oleu Wen behind
Same, but closer too
Boulders from across Llyn Idwal with Pen yr Hegli Du behind
Boulders just visible to the left of the llyn. View of Idwal slabs and Cwm Cneifion above – an ancient hanging valley.
My dog and field assistant Topper in 1999 after he had waited for me to negotiate a cornice on the headwall of Cwm Cneifion.
Boulders with Carnedd Llewellyn behind
Boulders from the moraines of Cwm Cneifion
Most of these photos were taken in August 2017 while leading a field trip for Harvard Summer School
For further reading
Darwin, Buckland and the Welsh Ice Age, 1837 – 1842, Proceedings of the Geologists’ Association 123 (2012) 649–662
And on his visit of 1831
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
Available here just-before-the-beagle