After leaving Cambridge in early 1831 Charles Darwin returned to his home – The Mount – in Shrewsbury
and decided to learn some geology in preparation for a trip to Tenerife, which never came off. At that time geology was not well-developed and all the strata belowed the Carboniferous (U.S.A Mississippian) was unknown. Sedgwick and Muchison began to unravel later that year, with Darwin in tow with Sedgwick.
a superb presentation of the Geological Column by Ray Troll, accurate and witty.
By early July Darwin had obtained his geological equipment and was especially proud of his compass-cum-clinometer. Here is his actual field bag and actual equipment, which is stuill the basis for field work today.
He also needed maps and he used Robert Baugh’s topographic map of Shropshire (wait for my next blog) and Greenough’s geological map of England and Wales. This is a photo of Darwin’s actual copy in Cambridge Univ Library.
After leanig how to use his clinometer on furniture he went into the filed to try his hand at field work. His destination was Llanymynech Hill some 15 miles west of Shrewsbury. I presume he travelled on one of the horses. His notes, transcribed below say NE, but that is typical of Darwin’s compass inversion, which he did both at Llanymynech and Cwm Idwal. If you don’t visit the sites and sit in stuffy libraries just reading his notes you’d never see this. You cannot do the history of geology without fieldwork, getting soaked, chased by irate cows and twisting ankles.
TRANSCRIPTION OF THE LLANYMYNECH NOTES,g
Llanymynech 16 miles NE [sic] of Shrewsbury; to the north of the village about ] of mile in an extensive quarry of Limestone. On the road to it, passed over a hillock of a soft slaty rock. some of the Strata were crumblingaway by exposure to the air. Strata very distinctly defined inclined at 78″. Direction ESE 6a 1i7N!7. The quarry is worked in the escarpment of a range of Carboniferous Limestone facing S by ]if. On the Eastern side & high in the hill where the stratification is better marked the rock more compact & of a redder colour. the seneral D is NE b N 14′. To the Westward & lower down D of st.ata is more NW 6< the angle lessl In centre there of quarry are several great cracks passing strait thrugh the rock now filled with clay. To this line the strata on each side are inclined on each side from [E crossed out] tOf 10″ & from [W crossed out] E 15o. It gives to the strata the appearance ofcurves. The stratification of the whole Western side appears to be less regular than that of the East. At one place I observed a series of strata having D ENE 10″ – The lowest Strata of Limestone that are worked consist of rocks of a softer texture, marked in patches by a brightish red, called by the’Workmen’bloody veined’Beneath there is the Delve consisting of avery argillaceous Limestone, soft & wastingaway on exposure to the air. it is not worth being burnt for Lime – The Workmen have never gone beneath this.
This has recently been put on the extensive website Darwin on line
Llanymynech Hill bounds the west of the Shropshire plain and his an extensively quarried limestone hill of 226 metres. The carboniferous limes lies on top of silurian slate (hill of slaty rock) There is a golf course on top for those who like to spoil a good walk and ther is a heitage trail. It is a hill I know very well as I have walked all over it and also done several of the rock climbs. On the visit I made all my measuresments i’d cycled the 11 miles from Chirk.
View looking ovber Breiden Hills
viewpoint with details for trail and on Darwin
Information board gleaned from my work
From Darwin’s notes it seems he came up from Llanymynech village and truned off on a lane at the bend GR266212.
The exposures are at the bend just up the hill. Continuing up you see the quarry cliffs and then need to find the paths onto them.
As you go up the lane you find the “slaty rock” with some obvious bedding. That was infuriating to measure as I found they dipped to the NW. It seems he was dyslexic – like the best of us. The strata were later seen to be Silurian.
Following up from those slaty rocks a path leads you into a quarry. This not as Darwin saw it as further quarrying took place for about a century. It is now abandoned and a haven for wild flowers and rock climbing. Some of the hardest routes are here, which I had to second rather than lead.
The limestne is well-stratified, with some interspersed muddy beds. Worsely is valuable on this. (The mud made for hairy rock-climbing in the rain.)
To read more, open up for my paper in the Brit Jour of the History of Science
Darwin at Llanymynech
Peter Worsley has corrected some of my conclusions on the mudcracks!
Darwin was baffled by the Bellstone in Shrewsbury, but in 1831 nop one knew that it had trundled down from Scotland on an ice sheet
After his next work on maps (my next blog) Adam Sedgwick arrived on the scene at the Mount. Big sis Susan took a shine to the reverend geological bachelor and his sister Caroline wrote to Darwin on the Beagle to say they expected Susan to become Mrs Sedgwick!! That would have been fun for historians.
So in August Sedgwick arrived and took Charles around North Wales in a gig and taught him a litte geology