A Brief History of the Somersetshire Coal Canal
The Somersetshire Coal Canal (SCC) was authorised by an Act of Parliament in April 1794.
The canal was promoted by the mine owners of the North Somerset coalfields as a cheaper means of transporting their coal to the markets in Bath and the surrounding area. (At that time the only transport was by pack-horse or horse and cart, over rough terrain. These animals could only cope with limited quantities, which resulted in high prices ).
The mine owners were also worried over the possible effect the flood of good Welsh coal might have on their market for there had been plans to import such coal into Bristol
Surveyed by John Rennie (of Kennet & Avon Canal fame), with help from William Smith (1769-1839) - (the "Father of English Geology", whose writings influenced Charles Darwin); the canal was to have two arms, with connecting tramroads, to the many coal pits in the Radstock and Timsbury areas.
(June 2001) A new and very-well reviewed book has just been published on William Smith.
(The book is:"The Map that Changed the World" by S Winchester. Penguin Books)
William Smith also built a tramway at Tuckingmill . I have marked the route on my Googlemaps feature
The original plan was for there to be a 3/4 mile tunnel at Combe Hay but this was later rejected becasue of cost and thus the canal became a "summit"canal. One problem with both of these arms was the climb/fall of 135feet.
Starting at Dundas Aqueduct, on the Kennet & Avon at Limpley Stoke, the main arm would pass to the west through Monkton Combe, Midford, Combe Hay, Dunkerton and Camerton to the basins at Paulton and Timsbury. At Midford the other arm would head towards Radstock via Wellow and Writhlington. The Paulton arm (or sometimes called the Dunkerton line) was constructed at two levels, the upper level from Paulton to Combe Hay, and the lower level from Combe Hay to Limpley Stoke. In later years, at the top of the Combe Hay part was a steam pumping engine (see later). However, at first, to "bridge" the daunting difference in altitude between these two parts, there were to be the three Caisson Locks (pic) at Combe Hay.
(Picture from The Daily Telegraph... "How the lock worked 362 kb file"; permission appied for).
These were experimental locks consisting of a large masonry chamber or 'cistern' in which a watertight box - the Caisson - was suspended. This box was large enough to take a full length boat, which was floated into it and then, with the doors closed, was raised or lowered to the desired level.
Adrian of the SCC has now completed an excellent series of diagrams to show how it works.
See Adrian's Caisson "how it works"
Although the maker - one R. Weldon was able to demonstrate the whole mechanism in working order, it was not a success. It is thought that this was because of the Fullers' earth rock stratum in this area. It, (like Cat Litter) swells when in contact with water; the masonary walls must have buckled and trapped the caisson. History & further details. It was replaced by an inclined plane (Nov.1801).
This appears to have been the normal double acting type where coal was craned from the barges in wooden containers capable of transporting about 1 ton of coal each. Three of these were placed in each wagon. This wagon descended by gravity, the 300 yards in 5 mins, pulling up empty waggons from below by means of a continuous pulley system with the heavy chains passing around two equal sized wheels at the top and bottom.
Excvation of a possible site for the caisson is now taking place. This lock was one of the "wonders of the waterway world"; its exact construction and mechanism is unknown. No matter how excited you may feel over its potential discovery please note that the site is on private land!
The inclined plane at Combe Hay was also unsuccessful, mainly due to the time consuming and inefficient trans-shipment of goods, and was eventually replaced, in April 1805, by a flight of twenty two locks, ( 3 had already been built near the bottom of the inclined plain).
One part of this new and costly venture was shaped like a bull's nose - still to be seen today. (See map). The large loss of water necessitated the building of a Boulton & Watt Steam Pumping Station capable of lifting 5 000 tons of water in 12 hours. It needed a water supply -probably from lock 19. From here it is proposed that an underground adit (with a fall of 1:40) took the water up the 'middle' of the bullnose to the engine.
This pump was later dismantled and moved to Dunnkerton to join a near-identical partner. If you click on Dunkerton pump you will see it (to the left). (Len Bampfylde collection)
Nearby was Dunkerton Wharf c1900. The cut from the coal filed to here was the first part to be opened and within 6 months 2 wagons per day were hauling coal from the wharf inro Bath at a cost of 2 shillings per ton, much less than previously.
We believe we have found the route of the adit! See:Adit map
"You will now find it is drawn straight and with two intermediate shafts - This is because Richard Hignett came up just before Christmas and found the spoil heaps from what appear to be the intermediate shafts. It all adds up to a straight adit. A very exciting find because it was made from a prediction based on engineering calculations, we didn't just blunder about and trip over the shafts. Richard actually reasoned where they should be and went straight to them. We are kicking ourselves for not spotting them before, one of them was only yards from where we were moving wood; but, of course, we didn't have his knowledge".
As you can see, this area at Combe Hay, is a very interesting one to say the least.
Click here for a detailed look at the history of Rowley Bottom and how the Caisson worked.
For some time we thought there was (good) evidence that the engine was built on the site of the old caisson,
(You may wish to compare this with a B&W blow-up of part of a redrawn 1810 map. If so, press this link:redrawn 1810 map around Caisson House
If only the SCC had waited until late 1800 they might have been very impressed by a "balance lock" invented by James Fussell IV (of Fussell's Ironworks fame) and built at Barrow Hill near to Mells on the Dorset & Somerset Canal . This was similar to the il l-fated Weldon design but had two caissons, in counterbalance, separated by a masonry wall.The inclined plane and extra locks might never have been! One site at BarrowHill has been excavated (July 2004)
(Caissons were also built on the not-too-distant Great Western Canal)
However, another, untapped (?) source has been found. This suggests that the first caisson was soon modified and that it and the "second lock" were much more like the design of Rowland and Pickering! Hard to believe I know! For more detail see: History & further details.
Why are there no pictures from this era? Because the world's first photograph by the Frenchman Niepce was not taken until 1827. Even then long-term fixing of the image was impossible. This had to wait until Daguerre's work in Paris 1839. Sorry!
The Society has actively conserved most of these locks. Although all wooden structures have long since gone, all the walls etc are intact. Regular working parties are held at the site. See later for details.
As to the other "arm", there are conflicting records as to its (economic) success. Engineering features include the tunnel near to St Julian's Church, recently excavated, and the sharp turn near to St Julian's Well. During this time (1805), the length of canal from Radstock to Twinhoe was built and to avoid the expense of further locks to take the canal downhill to Midford, a tramway was built.
Again, because of the trans-shipment of goods at Twinhoe and the low level of traffic on this branch, it was eventually decided to extend the tramway all the way into Radstock, using the towpath as the bed of the track.
Pics of Twinhoe basin ...now (&then?)This was 7 1/4 miles long, single track, with passing loops every 600yards. Teams of 3 horses would haul 8 or 9 wagons of about 11cwt each.
This would leave the only trans-shipment point at Midford Basin where this Radstock tramway and the Paulton canal arm met, converging over an aqueduct. (See the following pair of pictures)...and how it looks now after restoration!