It's probably true to say that we have come almost 'full-circle- in our deliberations about the caissons' locations, and that the work of the two academic heavyweights (Clew and Torrens) are again, believed to be correct
(From GoogleMaps). The three proposed sites are the small reddish rectangles with orangy losenges atop them. Sites 1,2 & 3 read from left to right. The 'Bull'sNose" shape of the trees is easy to distinguish to the north of Sites 1 & 2.
The latest version of these proposals is sometimes in direct conflict with the original theories as to their locations!. I have thus included these 'old' pages for not only are they interesting in their own right, but they include details as to WHY we think these caisoons are llocated as pictured above. It's instructive to compare the above map with this 1804 drawing:
Adrian's original map shown to the right...
The pinkish line signifies the proposed site of the tunnel between Caisson 1 & 2
Site 1 This is the 'traditional' site. Torrens obviously believes, as with Clew, that the caisson is here, as he points to 4 different pieces of evidence, all pointing to the same spot:
1. The 1796 Map & notes Smith-Cary map shows the the course of the caisson to the SW of the late inclined plane. (Hard to see!)
2. The Geological Evidence. The caisson was cut in the (approx.) 45 feet of Fullers Earth (with its characteristic small oyster fossil of Praexogyra acuminata) in this area. From a comparison with the Geological Map ("Frome") one can see that this starts at approx. the summit of the canal here, that is the 240ft contour.(The top wall must have been a few feet above this of course ..."so much higher than the upper canal as to contain a height of water just sufficient to cover the Caisson when opposite the upper level" (Farey 1806))
3. "Evidence from the 1810 map .. is crucial." (Torrens).(Shown above). The canal basin that probably served the top caisson can clearly be seen to the SW of Caisson House (CH on the map).
4. James Tunstall's "Rambles about Bath and its neighbourhood" (1876) mentions Combe Hay ("A lovely spot though art, Combehay" (sic)) and that the site of the caisson was near to Caisson House and marked with a chestnut tree. "The drop was 60feet and the walls are believed to be still perfect as when filled up".This tree sits atop a massive artifical mound which clearly is hiding something. Mitchell (1874) stated that " The flag-pole (see map 1 and 3) opposite Caisson House marks the site of the ill-fated Caisson"- "This cannot be as the effective depth of the caisson and its distance from the entry point (approx. on the 240ft contour line (250ft is marked on the map) do not match. However the most likely explanation is that the flag-pole marked the entrance to the second caisson!" (e-mail from Adrian) Clew originally thought that the site must be somewhere between the present remains of locks 5 and 6 in front of Caisson House. However he apparently now concedes that the chestnut tree marks the spot. (See map 1) Writing in the November 1999 'Weigh House", Clew obviously still believes that the caisson is here. The nearby hillock which was once partly excavated by Mr R Bilby and his son (for a school project). ..."They ... found many rusty nails and numerous stone chippings which seemingly came from 'dressing' stone blocks for further use. We wondered why this was done, not realising that Ray Bilby had discovered part of the caisson site." (p10).
Not unreasonably, Clew states that probably much of the stone work was taken away and used in the construction of the locks, rather than in the construction of Caisson House. Another piece of evidence is that the field by site 2 was later named "Caisson Field" and was purchased by the SCC on 24/02/1797. Why would they have needed to have purchased this land if not for the caisson(s)? The land around site 4 was not purchased until 27/05/1812, well after the demise of the caisson. In answer to this Adrian points out that it was the practice to lease the land before buying it. Good though all this evidence is (1) Why haven't we found anything during excavations, and (2) the Railway (see map) was built very close to site 2, and yet there is no mention of such a caisson in any such depositions!
Nov 2003. Excavations took place in the region of the fore-bay of lock 5 using a mechanical excavator ; nothing certain was found although it's possible that the filled-in tunnel and old tunnel floor was uncovered.
Possible locations of the Caissons