The Trevithick Society quiz night is here again. Come along for a great evening of fun at Liskeard.
Feel free to bring along some nibbles or ‘cakey tea’ and drinks; tea and coffee will be there as always.
Non members welcome (£2 donation). This will also be a chance to meet the new East Cornwall Branch team, and say goodbye to the outgoing team. JM.
Amazon seem to have removed the ability to edit my Amazon store, well they have from this Kinde HD6 App. So has a experiment, and means of occupying time whilst waiting on a cold station for my train here is a test of access to the Amazon authors page…
The Liskeard Mining District in 1863> Victorian geological map of Liskeard versus the modern Map
This blog will follow my digging (excuse the pun) into Brenton Symons Victorian geological map as I prepare for my talk next year to the Caradon Geology group. This post continues with the subject of the granite boundary by comparing Benton Symon’s 1863 map with a modern one published by the British Geological Survey. In comparing the two maps I hope to be able to verify how much use such a Victorian map is to those studying geology today, and maybe gain an insight into the accuracy of Brenton Symon’s work.
This series of posts are slanted towards those interested in the geology of the Liskeard area, but if your interests are cartography or Cornish mining history there may be some information of interest.
The BGS Map
I have chosen to expose to Mr. Symon’s cartography is BGS Sheet 337- Tavistock. A map now available on the excellent BGS website. The two maps are broadly in agreement (dates) on the rough course of the contact, so this post will concentrate on a selection of areas where the two diverge the largest.
The border compared
The first is the intriguing little kink in the Trecombe. Symons shows the Killas here forming a
estheticaly pleasing wave, its crest toppling to the west at the head of the combe. The BGS
version is far less pleasing to the eye, but displays some far more interesting geology. The modern map portrays the wave displaced slightly to the east, but more importantly has a NNW running fault replacing the western curve of the wave; a fault explaining the kink in the contact.
To the east of this point the two maps disagree on where the granite lies on the southern slope of Caradon Hill. The modern survey places it significantly to the norrt, a surprising discrepancy due to the importance of the South Caradon Mine. On the BGS map the contact is shown running through Holman’s shaft ( or as it is known now, the Man in the mine), partly following the Caunter Lode.
Moving on from there the two maps agree as they cross the East Caradon sett, but soon after rapidly part company. As it skirts the eastern slopes of Caradon Hill the granite boundary is shown running close east of the main road on the modern map, whilst Symons shows it further eastwards passing near to the round at Tokenbury, quite a large difference.
Inside the Marke Valley, just east of Minions Village the Geology gets more complex, this is the area of the overlaying killas tongue that influenced the minerals of Phoenix United mine. In 1863 this Killas was shown as having a curved form, but the BGS display it bordered by two faults. This slab of killas extends westwards across the South Phoenix Sett to a point just north of the Hurlers stone circle, much further then indicated by Symons.
Again, like at South Caradon Mine there is a major difference in the maps at the important mine of Phoenix United. Brenton Symons shows the mine being sunk on granite, with the extension of the rock reaching a point just east of Knowles farm. The BGS show a completely different situation. On their map only the western part of the mine, west of the Clananacombe, is in granite. However, what the modern map does show is a small outlier granited, an isolated outcrop close east of Knowles farm.
The northern part Symon’s map shows a simpler course of the boundary at it passes eastwards out of the coverage. The modern map shows the contact distruptted by faults, and its eastern extremity further west than indicated in 1863.
What are the key differences?
This comparison has revealed the main differences in the depiction of the granite/killas contact as:
In many places the granite contact is shown extending further into the surrounding country by Brenton Symons
The 1863 map shows a simpler course for the contact. Its course is formed of curves with no harsh lines caused by faults.
Within the two most important mines within the map’s coverage there are significant differences in the location of the granite.
The last point has certainly sparked my curiosity- which one is correct? My next little project will be start turning the pages of some of the books on my shelves to look for clues on where the granite really is. Unless of course any one reading this post already has information to answer that question.
For a copy of the complete 1863 map, and information about the mines in area see my book “The Liskeard Mining Area in 1863”.
The Liskeard Mining District in 1863> The granite boundary
Lying beneath Cornwall and Devon is a mass of granite that is the original source of their rich mineral wealth. An outcrop of the mass forms the highland of Bodmin Moor, its south eastern extremity marked by Caradon Hill, north of Liskeard.
The granite/killas boundary had a major influence on the pattern of mineralisation in the Liskeard area. Inside the boundary tin dominated, near the junction it was copper and some tin, and remote from the granite lead and silver was mined. Defining the position of the edge of the granite assists in understanding the history of mining in the area.
Brenton Symons’ map clearly shows this granite killas/ contact, and in far more detail than the current British Geological Society maps. Its soft shaded line waves its way around the north west part of the map, passing through many of the most successful mines of the the district.
Where is the boundary according to Brenton Symons?
Plotting the course of the boundary shown by Symons has some limitations due to the lack of on accurate datum of his map. Using field boundaries common to the modern Ordnance Survey maps it is possible, however, to obtain a good indication of its position.
The contact starts at King Doenierts Stone, goes to Tremacombe Head, passes up to Darite village , across the southern slopes of Caradon Hill to Caradon Farm, northwards pass Rondabury, into the Moor at Mutton Corner, does a loop back out to Phoenix House, another loop through Knowle Farm before leaving the map at Stanbury. A more detailed list of its waypoints is given later in this post.
The southern boundary of the contact has a relative smooth course in a WNW to ESE direction, with the only significant interruption an interesting sharp kink in Tremacombe. The south eastern corner is with the East Caradon Sett. The eastern boundary is far less regular with two distinctive waves. The peaks are shown within the Yolland Mine and Phoenix United, the troughs extending into South Phoenix and West Sharp Tor.
The Granite/Killas boundary waypoints.
For those wishing to plot the granite/killas boundary according the Brenton Symons’ here is some waypoints, along with indications of the status of public access to those position. In the next post I will be looking at the differences between this boundary and the one shown on the modern BGS maps. The waypoints are grouped by the mine sett in which they occur.
Wheal St Cleer
king Doniets Stone SX 23543 68819 Public access
Loop into fields to north SX 2360568947 No access
Wheal St Cleer Crossroads SW of Common Moor Village 23961 69000 public access
Caradon Vale(Hill)
North side of Penhale farm buildings
SX 24780 68839 foot path access
St. Cleer Consols
There is a sharp kick in its course at this point.
SX 25357 69129,
Tremarcoombe wall corner, at the edge of the open access ground
SX 25395 69280
Crosses the railway tracked, between the stream and wall. Open access ground.
SX 25297 69333
Lane meets field boundary at edge of open access ground at Treamar. The contact follows the wall NWly.
Caradon Consols
Apex of knick
SX 25324 69556
Crosses a lane close south of West Hendra farm, here the boundary runs E-W
SX 69484, 25526
Southern edge of Hendra farm buildings
Wheal Agar
SX 25883 69395
Darite school
SX 26223 69361
Crosses footpath
South Caradon Mine
SX 26680 69433
Road corner at Stanton Farm
SX 26800 69433
Road Corner
SX 26988 69492
South west corner of open access ground.
Caradon Wheal Hooper
SX 27196 69614
Higher Tretharrup Farm. Open access ground boundary wall.
SX 27341 69765
Crosses the farm boundary wall onto the open moorland, then passes close east of Kitto’s shaft of South Caradon Mine.
East Caradon Mine
SX 27805 70115
William’s Shaft, open access ground.
Glasgow Caradon
SX 28352 70208
Wall junction east of Caradon Farm
SX 28467 70419 Crosses the footpath to Tokenbury Farm
SX 28533 70550, Passes west of Roundabury, no public access.
SX 28601 70856, Crosses the stream at field corner, no public access.
Yolland Mine
The easterly apex
SX 28726 71106
No public access.
Marke Valley
SX 28141 71337
The junction of the lane to Ley Farm with the B road.
West Rosedown
SX 26749 71485
Crosses the stream at Mutton Corner, open access ground.
South Phoenix
SX 26340 71556
Railway track junction, open access ground
Phoenix
SX 26269 71840
Crosses upper cheesewring railway, open access
SX 26681 72107,
Junction of tracks outside of Phoenix house.
East Phoenix
SX 27235 72522,
Eastern apex, corner of footpath south east of Knowle Farm
Phoenix
SX 27110 72643
Knowle Farm, public footpath
SX 26832 72765
Crosses stream at northeast corner of open access ground.
West Sharp Tor
SX 26438 72870
Crosses the Henwood road at Stanbear
SX 26149 73167
Sharp Tor cottage, lane access, edge of open access ground
SX 26064 73277,
Apex, no public access
North Phoenix
SX 26646 73461
The road/track junction in Henwood Village
SX 26994 73465, footpath bend at edge of open access ground
SX 27258 73425, shaft, no public access
SX 27988 73883, Trevois Cross
A complete copy of Brenton Symons’s map is available in ‘The Liskeard Mining Area in 1863
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