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Summary

3.2 kilometre long canal tunnel through Morwell Down constructed between 1803-1817. The tunnel varied in width and height and the barges passed though it slowly; it took three hours to travel against the current to Tavistock, and two hours to make the return journey. Attempts to improve the situation in the mid-19th century, as the threat of competition from the railways intensified, were ultimately unsuccessful.

Location

Protected Status

• Listed Building (II) 1105707: SOUTH PORTAL TO THE TAVISTOCK CANAL TUNNEL AT NGR 448 702
• Scheduled Monument 1021461: Morwellham Quay: transport infrastructure, part of the water control system and a manganese mill
• SHINE: Structures, earthworks and below-ground mining features associated with Wheal Crebor Mine including a former canal and railway, east of Buctor Farm

Other References/Statuses

• Old DCC SMR Ref: SX47SE/29
• SHINE Candidate (Yes)

Monument Type(s) and Dates

• CANAL TUNNEL (XIX - 1803 AD to 1817 AD (Between))

Full description

Minchinton, W. E., 1973, Industrial Archaeology in Devon, 30 (Monograph). SDV7016.

Hedges, C., 1975, The Tavistock Canal. A Short History, 9-10, 18-19 (Monograph). SDV361772.

The course of the tunnel was surveyed and pegged out on the hillside and work began from each end in 1803. This involved boring through hard rock for a distance of nearly 1.75 miles and at a depth of 160 yards (146 metres) from the top of the hill. All the blasting was done with powder and the job took 14 years to complete. The method involved driving a small tunnel and then enlarge it by subsequent insertion of vertical as opposed to horizontal charges. There were shafts sunk all along the length of the tunnel to increase the number of faces that could be worked on simultaneously. For drainage, pumps were devised that were driven by a 40 feet (12 metre) water wheel driven by canal water. A further system ensured the tunnel remained ventilated.
Upstream movement through the tunnel presented difficulties, due to the flow of the canal and the constricting effects of the tunnel's width. Laden boats often took as long as 3 hours to negotiate the tunnel towards Tavistock, meaning only two boats could get through in a day. Legend suggest the boatmen propelled the boats through by lying on their backs and pushing with their hands and feet against the tunnel roof. Other sources suggest they used a stout pole with a v-shaped metal prong to pole against the tunnel roof.
In the 1850s a solution was suggested involving using a pressure engine to draw a tug (presumably towing a train of barges) through the tunnel on a rope. An alternative scheme was put in place in 1860 which consisted of two water wheels, one at each end of the tunnel, that pulled the boats through with a wire rope. However, the experiment did not continue as the rope damaged the stonework of the tunnel and involved frequent breakdowns.

Greeves, T. A. P., 1991, An Assessment of Copper Mining in Devon (Copper, Brass, Tin), 16 + 2 (Report - Assessment). SDV60709.

The tunnel is 3.2 kilometres long.

Greeves, T., 2003, The Tavistock Canal: A Review, 14 (Report - non-specific). SDV356552.

Greeves, T., 2003, The Tavistock Canal: A Review, 3-4 (Report - non-specific). SDV356552.

Ordnance Survey, 2011, MasterMap (Cartographic). SDV346129.

Morwelldown Tunnel marked on modern Ordnance Survey map.

Waterhouse, R., 2012, Tavistock Canal: Surveying a Forgotten Marvel of the Industrial Age, 37-38 (Article in Serial). SDV351508.

The canal tunnel was investigated in 2006. Although variations in height and width produced some very odd profiles, only in two places did the tunnel alignment significantly waver away from a straight line. Driving the canal through the living rock took 13 years of hard manual labour – powered rock drills were not developed until the 1870s. Environmentally stable conditions inside the tunnel preserved many artefacts, including spilled cargoes of limestone, coal and coke. Evidence for the workers is present in the form of abandoned tools, a tobacco pipe and even crude lighting consisting of long-since guttered candles fixed to the walls by dabs of clay. The prize finds, however, are pieces of early wrought iron barges. See article for full details.

Waterhouse, R., 2017, The Tavistock Canal. Its History and Archaeology, 38-73, 83-95, 361-380, Figs 3.26, 4.10-4.19, 5.1, 5.8, 10.72-10.104 (Monograph). SDV361789.

Construction of the Morwelldown Tunnel was a protracted and challenging process, started in 1803 but not completed until 1817. Ventilation issues and the hardness of the rock caused delays and a number of shafts were driven in order to increase the number of the ends that could be worked simultaneously. Waterhouse provides a very detailed breakdown of the construction process of the canal in his publication, covering the tunnel as a key component (see report for full detail).
The Tunnel Haulage Scheme, 1853-1861
During the mid-19th century (1853-1861), in the light of the potential competition from the new railway branch from Plymouth to Tavistock (opened 1859) providing cheaper rates of transport, faster dispatch and connection to the national rail network, the Canal Company attempted to update the infrastructure to increase speed and efficiency.
The main issue was the speed of boats traversing the tunnel, especially against the flow of the canal. Documents suggest the speed of boats through the tunnel was particularly slow, even by British canal standards, taking around 3 hours to travel upstream and 2 hours downstream. Aside from the fact that boats had to travel against the flow of the canal, the major difficulty was caused by the uneven width of and height of the tunnel, caused by the variety of rock types and the intermittent presence of the former pilot bore which caused the tunnel’s internal height to vary from about 9 feet to upwards of 18 feet in places. Some authors have speculated that ‘footing’ was used in the tunnel, commonly used elsewhere on the British canal network, although without any evidence. The boatmen are thought to have poled the barges through the tunnel, and the tunnel’s sides and in some cases the roof, are peppered with tapered indents, caused by the continued use of iron-shod poles to propel the barges along.
Waterhouse goes into detail regarding the potential solutions considered in the mid-19th century (see Hedges for summary). The initial solution came in the form of Mr A. Rowse’s idea of having a chain or wire rope passed down the length of the tunnel and wrapped around a water-powered winding drum at the north end. Boats could be attached to the chain/rope and hauled through by the wheel. The other option was to have boats pulled through by a steam-powered tug boat, although it appears that the estimated costs (between £300-£450) for this option was prohibitive. They fell back on Rowse’s rope/chain hauling idea and Thomas Knight, a self-styled ‘engineer’ from Gunnislake was appointed. As noted by Hedges (1975), this ‘solution’ was short lived, and by 1861 the apparatus was being offered for sale by auction, having been described as being used for a ‘very short time’ in the tunnel. This was the last attempt by the Canal Company to improve its prospects. It was to survive as a waterway for another 12 years, in a steadily declining state.
Waterhouse includes references and images of the damage caused to the walls of the tunnel by the wrought iron boats.
In the Archaeology chapter, Waterhouse includes detail from the two surveys carried out (c.2005); one of the tunnel's internal features, the other of the surface features. This comprehensive investigation includes detailed measured survey of underground features, while the surface features were annotated onto maps and paced surveys of earthworks. See report for full detail.

Sources / Further Reading

Associated Monuments

Associated Finds: none recorded

Associated Events

• EDV8013 - Survey of the Tavistock Canal Tunnel on Morwelldown

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