Walking the Old Great North Road, Dharug N.P., Part Two

This sign reads: There's a story that this naturally formed rock shelter was used as a place to hang convicts.  Supposedly, a noose was suspended from a tree growing above the hole in the roof of the shelter.

The story goes that convicts were tried by Percy Simpsom at Courthouse Cave above Wisemans and the condemned men transported across the river to this site.  The convict was then led to the side of the hole, those noose placed around his neck and his feet knocked into the hole-thus hanging him.

It's a good story, but there is no proof that Hangman's Rock was ever used in this way.  It was obviously used for some purpose, as the excavated steps, that floor area and bench seat were carefully constructed.

A more prosaic explanation is that the hole was roofed over the cave used as a storage area for gunpowder.  Peraps it was just a place for the overseers to sit and watch the work on the road.  Its exact purpose will probably never be known.

This signage reads:
In 1858 a 40 metre section of the road's retaining wall collapsed into the gully below the road.

The impressive buttresses-keyed to the wall with L-shaped blocks-were intended both to add strength to the wall and to contain the exits for the culverts which carried storm-water under the road.

The storm-water discharged from these exits flowed down the races built into the face of each buttress to the open spillways below.  These directed the flow into the gully, away from the base of the wall, preventing undermining of the foundations.

Why did the wall collapse?
It is likely that the drainage through this section of the wall became blocked by silt and debris, causing the filling material behind the wall to become waterlogged.  The increased weight and pressure-combined with the builders' mistake of not keying the buttress to the wall below the culvert exit-forced the base of the wall outwards and the section slid downhill.

Studies of the collapsed section tend to support this theory, as the centre part is still intact, but has moved outward and downwards from its original location.

Part of the retaining wall which now supports the narrow section of road above the collapse is convict built, and probably formed part of a work platform area where the blocks for the main wall were manufactured.

The remainder of this wall was built sometime after the collapse from roughly split stone blocks, possibly at the same time as the building of the road to St Albans, as the stonework is the same quality.

In 1998, the NPWS undertook a partial reconstruction of a collapsed culvert, located on this buttress.

amazing how you find, just the one plant, unknown, in flower. 

walking back again now

Unfortunately, the Rockwarblers weren't sighted, but it was still  a very interesting walk