Blackheath Cavern - the great column of 1794

Until now the earliest account we had of the Cavern was Helme's 1800 description. But now we can go back even earlier - to 1794 - with John Bew's Ambulator or a pocket companion in a tour round London (plagiarised by Helme). Bew gives us a fascinating new feature to ponder, now lost or inaccessible: a great column 43 yards in circumference. If circular, that would give it a diameter of some 40 feet; columns of this size rarely collapse, so it's probably buried in choked passageway somewhere in the Cavern complex. A cropped copy of the wartime survey is shown below as a reminder that there were certainly no columns/pillars to be seen in 1939.

Blackheath Cavern: missing pieces of the puzzle

Pinnock's 1833 The Guide to Knowledge¹ is a critically important account of the layout of the Cavern. During the first half of the 19th century access to the cavern was by a "flight of steep steps cut in the chalk for about forty feet." The first chamber encountered at the bottom of the steps was "about thirty-five feet in length, varying from fifteen to twenty feet in breadth, and about twelve feet high." What follows next in the account is extremely interesting, because it describes a small person-sized tunnel that is now lost:

"...the guide next took us through a narrow confined passage in the rock, which is about six feet high, from two to three feet wide, and extends in a winding direction for about twenty feet, and gradually declining for about three feet, brought us into the first portion of the large cavern represented as above [a well-known engraving of the main chamber]."

So the original staircase, the first chamber, and the small winding passage are all essentially lost/inaccessible - although in 1939 Legrand, Sutcliff and Gell clipped original parts of Cavern wall twice while sinking their shaft and driving their exploration tunnel from the bottom of the shaft towards the main chamber as we see it today:

"...at a depth of 32 feet, the floor of the excavation [ie the shaft] began to give way, the workmen finding themselves in a small cavity, which appeared from inscriptions found on the chalk to be part of a passage leading to the cavern." (Craske 1946)

"...about 57 feet horizontally from the foot of the shaft, the original tunnel was again encountered, very close to its point of entry to the main chamber." (Craske 1946)

Pinnock's small "winding" tunnel almost certainly still exists, because this type of small passage - with a great thickness of chalk above it - tends to be extremely strong and resistant to collapse. It's probably just choked with sand/chalk debris, and given time could be found. But it seems that the first chamber has collapsed - which may be related to the hole found during foundation works for the northern end of the Undercliff flats. Borehole No.2 drilled by LSG in 1939 may have passed right through the collapsed/choked remains of the first chamber, with the drill dropping through space for 18 inches after passing through a 3-foot thick chalk ceiling. The drill then proceeded through 20 feet of disturbed ground before hitting a firm chalk floor. However, the first chamber was said to be only 12 feet high, which doesn't tally.

There is a remarkable implication here. If the small winding person-sized passage was the only way into the main chamber, then how was mined chalk brought out? It would be like mining through a keyhole. No chalk mine we have ever examined has an arrangement like this, which raises a fundamental question: is the Blackheath Cavern actually a chalk mine?

Pinnock also hints at a lost chamber concealed behind a piece of stone in what we now call the Inner Chamber, next to the "Bar":

"...at the top, in the chalk, there is a large piece of stone which would almost seem to have been placed across the entrance to a fifth cavern; but as we were not prepared to remove the earth, this remains only a conjecture."

Very slowly the evidence seems to be nudging towards the seven "apartments" originally described by Helme in 1800 (even then major falls had already occurred, with two high domes in the Thanet Sand).

Click the images above for slightly larger versions

¹ Pinnock's account was later plagiarised almost verbatim by Dunkin in 1855.

The oldest known photograph of denehole exploration

In this 1866 photo we see the father of denehole exploration, F.C.J. Spurrell, as a young man - indeed this is thought to be the only surviving image of him. The picture was taken at a noteworthy four-pillared denehole at Stankey, Bexley. Also present on this excursion is Sir John Maryon Wilson - underlining Sir John's considerable knowledge about deneholes located on his estate at Charlton and nearby at Hanging Wood.

Left to right: FJS [Spurrell senior], FS [Spurrell junior], AS [Alfred Spurrell], Capt. Popperwell, HS [Herbert Spurrell], and Sir John Maryon Wilson.

Click image for a slightly larger version (781 x 544)

Mr Brand's Cavern

Chalk mining and sand extraction to the north side of the Blackheath Hill roadway was disrupted (although not stopped) in 1751 when "the Crown proceeded against Morden College, to restrain the trustees from granting leases to dig for sand and chalk under Maidenstone Hill". Leases previously granted (illegally as it turns out) to three enthusiastic excavators (Messrs Harding, Steers, and Hatch and Nightingale) had expired in 1734. Whether sand and chalk extraction continued after 1751 is unknown - it would have depended on how brazen and unscrupulous the diggers were, as well as exactly when the original leases granted by Sir William Boreman were shown in court to have been illegal. Ultimately it wasn't until 1771 that concrete legislation was enacted that explicitly stated "no sand or chalk [to be] carried off the waste".

Click for larger version (303k 856 x 1154)

The name of Steers always seems to be tied to the Blackheath Cavern, even though there is no documentary evidence whatsoever that the Steers family ever set foot in it. In any event the characteristics of the Blackheath Cavern galleries are those of two or three centuries earlier; it was already long disused in Steers' era . All that is certain is that Steers was fined for undermining the King's highway - no inference should be drawn from that regarding how prolific a tunneller he was. Harding or Hatch and Nightingale are just as likely to have been carving out galleries in the chalk without keeping any plans of their activities - the root of the problem we face today, exemplified by Winn's Chalk Mine, which is almost certainly the work of one of the three above-mentioned operators.

Galleries in the chalk were open in the vicinity of Maidenstone Hill before the rediscovery of the Blackheath Cavern; we know this because of the 1751 court case in which the Crown took action against Morden College; Mr Brand, for Morden College, suggested that the excavations under Maidenstone Hill "might puzzle future antiquaries". There is no evidence that he was referring specifically to the Blackheath Cavern, although if he was, that means that the Cavern was already open in 1751, thirty years before its official "rediscovery". Just how many times can the Cavern be rediscovered? It's just as likely that Brand was talking about other accessible chalk galleries nearby. Incidentally, there is a small chance that Brand's comment is from the 1771 Exchequer Court case, which nevertheless would still prove the existence of open chalk mine galleries nine years before the Cavern "rediscovery"; Hasted is frustatingly vague in the chronology.

Previous commentators have misread this page of Hasted, failing to notice that Brand's suggestion that the chalk excavations would puzzle future antiquaries was made at least nine years before the Cavern's 1780 "rediscovery" and probably thirty years before it. This is a critically important detail. Further research may be able to tighten up the exact date of Brand's statement.

The page above from Hasted mentions in passing the Commissioners of Greenwich Hospital asking the Crown Officers for help to prevent damage to the conduits on Primrose Hill (now Vanbrugh Hill) and Conduit Vale (now Hyde Vale) - both caused by ballast digging.

Well in the secret garden, Park Vista

A well was recently found in the Dwarf Orchard (the walled garden adjacent to Park Vista). The photo below (photographer's name witheld, although the person was clearly of unusually tall stature - the wall just here is some 10 feet high) shows the general situation:

Graham Keevill of Keevill Heritage Consultancy has come to the rescue with some very clear photos of the well, both before opening and then looking down the shaft:

© Keevill Heritage Consultancy

© Keevill Heritage Consultancy

The well is 9-10m deep, with an internal diameter of 1.2m approx; the capping stone is 0.75m diameter with a bevelled edge plus two iron lifting rings¹.

¹ The Orchard, Greenwich Park: archaeological evaluation report. Keevill Heritage Consultancy, final issue 30 March 2010. Graham Keevill and Catherine Underwood.

The price of conduits

A fascinating note of how much was being spent on the Greenwich Hospital conduits has come to light. Dated 1727, it concerns "Conduits and Aquaducts" (sic), giving a figure of just over £2,257 - a very substantial sum of money at the time. It's not known over what time period this expenditure occurred. Click image for a slightly larger version.

Stunning new conduit portal image discovered

An incredible new image of a grand conduit portal has turned up. This is the first time either Per or I have ever seen this image, and we've been looking hard for 25 years. It's a major discovery, although we're not sure which conduit it is; much discussion will now take place. It might be the original entrance into the Hyde Vale Conduit, set into the pit alongside the Standard Reservoir Building. But right now we simply don't know. It's quite a grand portal - befitting a major conduit. I must admit I almost fell off my chair when I first saw this. It's an incredibly rare find. Click image for a slightly larger version.