Bells and Bardon

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Over the weekend of 20th/21st/22nd October, the OUGS Wessex Branch visited our area to study the rocks of Charnwood Forest. I joined them for their Saturday activities, meeting them at the Great Central Hotel in Loughborough. The morning was spent at John Taylor's Bellfoundry Works and Museum (Photograph 1) where we were given a presentation about bells, and then had a guided tour of the museum and works. The Bellfoundary is the largest in the showing some bell casts and the sand pit.world; one of only two surviving in the British Isles (the other is at Whitechapel in London); has been located in Loughborough since 1838; and has the distinction of casting the largest bell in the country - the 16 tonne Great Paul for St Paul's Cathedral. During the tour we were told about a variety of different kinds of bell including cowbells, handlebells, crotal bells, hemispherical bells, handbells, church bells, tubular bells, and carillons; and also had demonstrated the important differences between bronze and brass bells, tuned and un-tuned bells, cracked and non-cracked bells, and how minor differences in manufacture can affect the sound and resonance of the finished product. The remarkably complex foundry process itself was also described; from how to prepare a core and case, to smelting the bell metal (an alloy of 23 % tin and 77 % copper) at 1 200 °C, to burying the mould in a sand pit so the mixture doesn't cool too quickly, to the inscription process of lettering and imaging and the requirement to be able to spell backwards, to the final tuning and polishing. A fact not realized by most of us in the group was that a bell doesn't have a single note. In fact, on careful listening, most people could differentiate two or three notes depending on where the bell was struck, and the trained bellmaster can identify up to twenty different tones.

The afternoon excursion was to Aggregate Industries Bardon Hill Quarry near Coalville, (Photograph 1) the rocks of which are part of the Charnian Supergroup (Figure 1). Bardon Hill itself is the highest point in both Charnwood Forest and Leicestershire at 279 masl/921 feet asl (to three significant figures!), and the Quarry extracts 3½ million tonnes of stone per year (approximately 12 000 - 14 000 tonnes per week). Much of the stone is taken away from the site by rail in the company's white and silver bogie hopper wagons to terminals at Washwood Heath (Birmingham), Harlow Mill (Essex), Thorney Mill (near Heathrow Airport), Angerstein Wharf (east London), and Brentford (south west London), by Freightliner's Canadian built Class 66 diesel locomotives.

The quarry is connected to the National Rail networks Birton – Coalville - Leicester line by a spur into the private quarry complex, which is worked by the two Bardon owned industrial diesels 59 "Duke of Edinburgh" (Rolls Royce 6wDH 10273 of 1968) and 159 "Bardon Duchess" (Thomas Hill 6wDH 297 of 1981). We watched the “Bardon Duchess” shunting in the yard before it took a rake of loaded hoppers to the exchange sidings. Once kitted up in our high-vis jackets and hard hats we boarded two Landrovers and were driven into the quarry workings. Quarrying further into the hill itself is not allowed as it has been set aside for wildlife and human recreation, so the workings are now heading deeper into the earth, and another six or seven levels are planned, adding to the current eight or nine levels. Trial borings have confirmed the presence of the required rock at deeper levels so the quarry is far from being worked out. First we were taken to Pit 12, (Photograph 3) the current lowest point of operations, and were allowed to rummage in the piles of tuff nearby, and marvel at the views of Permian and Triassic rocks showing bedding and cleavage at opposite angles, and the fifty to sixty meter deep wadis which had to be removed before the rock could be quarried. We had to be aware of the massive Caterpillar 777D tipper trucks which were constantly shuttling backwards and forwards. These giants cost £½ million each, weigh 40 tonnes, and can carry a payload of 100 tonnes. These impressive beasts were handled easily by their drivers. We were then transported to two higher levels where we could view the Precambrian volcanic sediments and lavas of the Bardon Hill Volcanic Complex (Photograph 2) containing extrusive igneous rocks, and Triassic rocks of the Mercia Mudstone Group which overlay the Precambrian, in more detail. In the Triassic, the Charnwood Forest area was a dust desert, containing inselberg hills (including those we now know as Bardon Hill, Mountsorrel, and Breedon Hill), with a very high saline water table.

The Charnian volcanoes produced little flowing lava, being more of the highly explosive pyroclastic variety. Over fifty minerals have been found in the Forest, including traces of gold in the 1880s. The most common examples are quartz and calcite, and various copper minerals such as malachite, azurite, and cuprite have also been found on-site. The 'local' rock, the Bardon breccia, is an igneous volcanic breccia which formed in the volcano conduit when the magma cooled and eventually broke down. This fracturing is likely to have been caused by the injection of hydrothermal gases and fluids. We were shown a sharp unconformity representing a time gap of 400 Ma; a major fault zone which runs through the quarry; rheiodal folding of rocks; and stood in the conduit of the Bardon volcano. (Photograph 4).

Photograph 1: View inside Taylor's Bell Foundry, Loughborough   (Photograph by Paul Atkinson)	Photograph 3: Viewed from Pit 12 of Bardon Hill Quarry, the  current deepest level of excavation: tuff in the foreground, with Permian and Triassic rocks behind with bedding and cleavage at opposite angles, topped by soil overlay. (Photograph by Paul Atkinson)
Photograph 2: A general view down into Bardon Hill Quarry showing the previous levels of excavation   (Photograph by Paul Atkinson)	Photograph 4: A 'V'-shaped fault occurring in the rock near the conduit of the Bardon volcano. (Photograph by Paul Atkinson)

The group collected various samples including quartz, hematite, epidote, schist, quartz intrusions, Bardon breccia, mudstone, and examples of ash fallout layering. The sediments of the Bradgate Formation are turbidite beds resulting from sediment-laden currents, and examples of rippling were in evidence. The lower sections showed coarse-grained breccias, which gave way to finer-grained sandstones, mudstones, and siltstones higher up the sequence. A brief rain shower created the lovely sight of a rainbow which arced in over the top of the hill and disappeared deep into the quarry workings. Unfortunately time and daylight were fast racing away, so it was into the Landrovers once more and back to the cars for the return to Loughborough. It had been a most educational and enjoyable day. With thanks to: Debbie Tabner (OUGS Wessex Event Organiser), Keith Ambrose (BGS and Tour Leader); Robert at the Bellfoundry; and our chauffeurs at Bardon Hill.

Figure 1: A simplified lithostratigraphy of the Charnian Supergroup [Adapted from Anon (2006), p. 9].

References and further reading:  

Allaby, A., & Allaby, M., 2003, Oxford Dictionary of Earth Sciences - Second Edition, Oxford University Press, Oxford, p. various.  

Anon., 1999, Look at Taylor's Bell Foundry and Museum, Bessacar Prints, Doncaster, p. 1 - 6.  

Anon., 2006, Fieldtrip to Charnwood Forest, (Trip notes handed to participants), p. 1 - 4 & 9.  

Hackett, E., Billinghurst, C., et al., 2006, Industrial Locomotives: Handbook 14EL, Industrial Railway Society, Melton Mowbray, p. 124.  

Rawlinson, M., 2006, Freightmaster #43 - Autumn 2006, Freightmaster, Swindon, p. 137.

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