Newhailes, Shell Grotto

NT 32543 72705 In September 2011 a further investigation was carried out on the masonry remains exposed in 2001 and 2002 just below and to the W of the Shell House. The S half of the feature previously excavated was uncovered, revealing the water cascade flowing down to the edge of a large, shaped pool (now infilled). This trench was then extended to reveal a further level of the cascade and the relationship between the cascade, the pool and the underlying culvert. The project was attended by school classes, volunteers and drop-in groups as part of the launch of Archaeology Scotland’s Archaeology Month.

Water emerged from a brick-vaulted culvert and fell down three semi-circular stone cascades (now largely robbed) before falling into the pool itself. Each tier was lead-lined and bounded by ashlar flanking walls that stepped out at each level. The latter were capped with ‘rockwork’, consisting of fragments of industrial (possibly smelting) waste to match the facade of the Shell House behind. Several fragments of sponge, an artificial coral-form rockwork, were found loose within the feature, apparently part of its decoration.

Excavation to the E revealed the continuation of the brick culvert vault to the E of its mouth, and a layer of white quartz pebbles that covered the ground above. The culverted river was secondary to the partial infilling of the pool and suggests that the original clay lined pool was river fed in addition to the cascade water. The entire pool was then infilled and trees planted. A small trench excavated further to the W across the pool edge exposed an orange blaize path leading to the nearby stone bench.

It seems likely that a structure stood in the location of the current Shell House (1770s), which may have related to the laying out of the water gardens in the 1740s. The current structure is slightly off-centre to the cascade, with the rockwork as a secondary intervention to parallel the Shell House decoration.

The feature had been fully infilled by the early 1790s, but evidence (plaster, mortar and stonework) seems to point to initial dumping of debris into the pool. This activity may relate to the 1770s phase of the Shell House construction. The cascade is similar to many water garden features found in association with grotto structures around the country.

Archive: Connolly Heritage Consultancy and the National Trust for Scotland

Funder: The National Trust for Scotland, Archaeology Scotland and BBC

Connolly Heritage Consultancy 2011

Now roofless, the grotto is rectangular in plan measuring 6.4m by 5.4m and is 4.9m in height. The grotto had a single pitch, slated roof until the 1960s.

Built in the mid-18th century, and modified in 1781 the grotto originally looked over a large artificial pond that formed part of the Newhailes water garden. The pond, now filled in, is still visible as a long rectangular depression aligned N/S. On the far side of the pond was a stone bench, surviving as a pair of upright stones, positioned to provide a place to look back on the Grotto.

The principal (west) elevation is constructed of random rubble punctuated with projecting water-washed boulders and decorated with furnace slag (possibly waste from copper smelting) and sponge-stone (commonly termed ‘tufa’), both of which are bedded in mortar and held fast by iron angles (which are particularly in evidence at the top left-hand corner of the facade). The elevation is centred by a wide, segmental-arched opening formed by substantial, deeply-vermiculated voussoirs and rybats. Documentary records and archaeological work in 2001 & 2002 have demonstrated that the Grotto was decorated, both internally and externally, with shells (local and exotic), glass and minerals (including quartz).

The south, east and north elevations are of random rubble. There is some evidence of harl to each wall suggesting that they were either rendered or, more probably, harl-pointed. Near the base of the south face at its eastern end is a single rectangular opening. There are two further openings (one above the other) at the northern end of the east face. Each opening leads into the wall, forming a system of interconnecting flues. A fallen chimney, along with a stoke-hole/’oven’ at the base of the east wall in was revealed during excavations in 2001 & 2002. The presence of soot within the flues suggests that they were used to exhaust smoke and steam, rather than to heat the grotto, adding to the atmosphere around the building.

The interior consists of plain harl-pointed rubble walls with dressed and coursed-stone pillars at the angles all set upon a continuous dressed-stone plinth. Those walls to the north, west and south each possess two rows of dook-holes, some of which still contain the timber dooks. These were used to support the timber lining of the grotto, uncovered during excavation in 2001, and consisting of mortar covered boards set with shells and stones. The angle pillars appear to have been decorated on the hard, with that to the south-east corner still bearing some clinker, quartz and pebbles all held with straps. A newspaper clipping of 1919 illustrates part of the decorative scheme. It depicts either the south-east or the north-east corner of the grotto, showing that the decoration comprised entirely of stones, slag and shells arranged in various patterns: simple inter-lacing to the east wall and ‘gothick’ arcading to the north set beneath shell-work, spandrels and cornicing. The floor is a diamond pattern and is made up of polished sandstone flags with black marble square inlays set diagonally across the building.

In 2002 the masonry feature partly revealed to the W of the Shell House in evaluation Trench 49 was fully excavated. The feature had been set into the sloping bank running between the Shell House and the former pond. The original trench had revealed a low brick vault spanning an opening of about l.0m in width. The walls of this feature were ashlar-lined and were found to angle back from the sides of the opening, to the N and S respectively, before returning to extend westwards once more. The upper surface of these westwards-running walls sloped down to the W, following the profile of the pond-side banking.

The excavation showed that the feature had once formed a small water cascade, on three levels, each wider than the last. The upper level consisted of a fall (ca. 0.5m) at the tunnel entrance (actually a low ceilinged water conduit); a second level occupied the upper step-back of the flanking walls and consisted of a shallow pool with projecting edge defining a second fall (0.65m) to the W; and a third lowermost level where a further step-back of the flanking walls defined a second shallow pool whose W side also extended out to the W where it was defined by a stone lip over which water finally flowed into the shaped pond below (ca. 0.6m fall).

Excavations in 2011 further revealed the cascade walls, confirming the symmetry as well as suggesting that each level of the cascade may originally have been lead lined. A trench on the western edge of the pond found that the pool had a soft edge, rather than the formal ashlar blocks on the eastern side. Remains of the 18th century path leading to the stone bench were also uncovered.

(Information from the National Trust for Scotland, January 2013)

Information from NTS