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Fussells Trial Balance Lock


Strung out along a secluded valley at the extreme eastern end of the Mendips in Somerset are a number of strange structures which appear to have served no purpose. At Edford there is a canal bridge in a field and in Coleford there is a spectacular aqueduct, high above part of the village, apparently connected to nothing whatsoever. Not far from Frome is the remains of a staircase of what appear to be deep, strangely misshapen, lock chambers excavated into a hillside.

A Lock Chamber at Barrow Hill

These are some of the surviving remains of the Nettlebridge branch of "The Canal the Never Was", the Dorset and Somerset Canal. Started in 1796, it was never completed and many of its engineering features have been shrouded in mystery and were believed lost forever. With the formation of the Dorset and Somerset Canal Study Group in 1995, the scattered pieces of information have been gradually brought together and a clearer picture is emerging of how the canal was intended to have been built. This research was not helped by the fact that the Company Records have disappeared without trace.


Of particular interest was the involvement of James Fussell (1748 - 1832), a shareholder in the canal and an ironmaster who had established an edge-tool works at Mells, near Frome, not far from the line of the canal. He had a number of patents to his name and one, No.2284, was worthy of special attention: it was for a "Balance Lock for Raising and Lowering Boats, &c.; applicable to other purposes". No wonder those lock chambers looked a little strange, they were not intended for ordinary locks but for something quite revolutionary.

Fussell's Balance Lock was a 2-tank boat lift which pre-dated Anderton by a very long way and was the very first of that kind in the world. Fussell was a specialist chain designer and he hit upon the idea of using his newly invented sprocketed chain to synchronise the movement of the two ends of the long tanks of water. Without this invention to hold them level, the tanks would have been unstable and the water would have sloshed to one end and capsised them.

The large masonry structure containing the tanks was divided into two chambers and let into a hillside where the canal changed level. The staircase of lock chambers had evidently fallen victim to the canal's premature demise and was never completed - but there was tantalising evidence that an earlier "trial" balance lock had been built elsewhere on the canal to test out the principle &emdash; and that one had actually worked.


Searching for the Site

After much head-scratching, the search homed-in on a section of canal on a private estate where a change of level seemed to occur inside a densely-wooded valley. With the landowner's permission the area was cleared by work parties from the D&S Group and the Somersetshire Coal Canal Society (who have a particular interest in boat lifts of all types). The only clue that anything might possibly lie beneath the surface was a couple of dressed stones which appeared to have been laid as a course of masonry. Further work with a pickaxe revealed that this indeed had been the site of a structure and, with archæologists on hand, a large excavator was brought in to see what else might be found.


Clearing the Site by Hand in Preparation for Excavation

The result was vastly beyond anyone's expectations - the excavation opened up a masonry chamber 30 ft. long, 8 ft. wide, with other evidence suggesting that the structure had probably been over 30 ft. high. An archway at 'basement' level appeared to lead to a second parallel chamber, now filled with rubble, making the whole thing 24 ft. wide.

At this stage it was decided to analyse the results and sort through the evidence which had been found, before contemplating further excavation. The excavation of the second chamber was undertaken the following year and revealed a similar structure and an even greater quantity of artefacts.

Both Lock Chambers Revealed     
Click here for larger picture

Artefacts Found During the Excavations

A piece of leather
A caulking iron
Some nails
A hook


Although the structure appears quite robust and has shown no signs of serious movement yet, it would be a shame if winter frosts were allowed to wreak havoc with the newly-revealed stonework. In the long term, it seems likely that the only practical way to preserve the structure will be to fill it in and give the archæologists of 100 years hence the same thrill we experienced, when it is their turn to discover it again.


More information about Fussells from: Fussells Iron Industries Society


Contact for further information:

Derrick Hunt,
43, Greenland Mills,

BA15 1BL


Paper on Fussells Balance Lock Excavation


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Fussells Trial Balance Lock