The Hardy Monument is a monument on the summit of Black Down in Dorset, erected in 1844 by public subscription in memory of Vice Admiral Sir Thomas Hardy, a commander at the Battle of Trafalgar. Admiral Hardy lived in Portesham and his family owned the Portesham estate which stretched from the middle of Portesham to Black Down. The site for the monument was chosen because the Hardy family wanted a monument which could be used as a landmark for shipping. The monument has been shown on navigational charts since 1846 and is visible from a distance of. The monument is situated on Black Down, a hill overlooking the English Channel near Portesham in Dorset, England, on the road between Abbotsbury and Martinstown. It was restored in 1900 by his descendants and bought in 1938 by the National Trust for the sum of £15. The monument was designed to look like a spyglass, as Admiral Hardy would have used on board ship. Its eight corners are aligned with the compass points. Viewed from the ground the corner to the right of the lightning conductor points due south. The bench mark on the northwest face denotes the altitude of Black Down at. From the top of the monument at a height of above sea level it is possible on a clear day to see the coast from Start Point, Devon to St. Catherine's Point on the Isle of Wight, both of which are distant. To the north can be seen Pen Hill in the Mendip Hills which is away. The monument was closed to the public in 2009 when major renovation work was required. This work was completed in January 2012. To date, the monument is regularly opened during the peak season, where visitors can climb the 120 steps to the viewpoint at the top. The heathland area around the monument was in 1984 designated a Site of Special Scientific Interest, when the Nature Conservancy Council decided that the geology of the area was very rare. Adjacent to the monument is a stone seat erected in memory of Lt Col William Digby Oswald who was killed on the Somme in 1916.
Geology
Geologically, Black Down is the western tip of the Bagshot gravel beds. The gravel beds extend to the east as far as London. The ground around the monument is pitted with various holes and craters. Many of these are dolines or swallow holes. These are formed when rain falls on the highly acidic topsoil. The water increases in acidity as it percolates through the topsoil then dissolves the underlying chalk. Eventually there is nothing but topsoil above the caverns so formed and the familiar shape of a doline is created when the topsoil collapses into the cavern beneath. Dolines are usually shaped like a teardrop cut in half vertically and laid down horizontally. Within of the monument there are three dolines which were formed by the chalk being dissolved in a vertical fissure in its structure. These dolines are vertically sided and are shaped like wells. The two which opened up in 1956 are some deep. The one which opened in 2006 is not quite vertical and its depth is unknown.
Geodesy
The Hardy Monument was the origin of the 6 inch and 1:2500 Ordnance Survey maps for Somerset and Dorset.
