Over the centuries land-owners and farmers have developed many methods for separating and distinguishing areas of their property. Walls, fences, hedges and ditches are all common. In Yorkshire dry stone walls are the most frequent type of land boundary employed. Dry stone walls, with an estimated length of 5000 miles, are a major landscape feature of the Yorkshire Dales; these can be of considerable archaeological and geological interest. The walls are ‘dry’ in the sense that no mortar or clay was used to bed their constituent pieces of stone. Unmortared walls are not of course restricted to land boundaries. Locally we have examples of dry stone retaining walls, but dwellings could also be of dry stone construction with mud, straw or heather being used to seal the walls to provide draught exclusion.
The precise technique for building a wall varies throughout the country. They may be built directly over solid rock but a common constructional practice was to start by cutting a narrow trench and filling it with small stones. A foundation course of larger stones is laid on top of this. Thereafter the wall is built up in progressive courses of inner and outer stones which are usually given a ‘batter’, that is a progressive narrowing to the top. The centre of the wall is filled with rubble. Approximately half-way up, since the eighteenth century anyway, a layer of ‘through stones’ were laid across the wall to tie it together. Walls are generally topped with copings, a row of slanting or vertical stones. The shape of coping stones is subject to considerable stylistic variation. An example of a completed wall here in Heaton is illustrated.
Naturally these walls would have to allow the movement of stock and so are provided with sqeezes or ‘sheep-creeps’. In some cases the layers of stone above a creep can be removed altogether to create an opening large enough for cattle to pass.
The selection of walling materials naturally depends on local geology. In Yorkshire three types of stone are used: limestone, sandstone, and millstone grit. Underneath some coal seams is found a highly siliceous sandstone called ganister. This was valuable as a material from which refractory bricks could be made. Nonetheless ganister also finds its way into walls in mining areas, as may that synthetic stone – iron smelting slag. In other parts of the country granite and slate are frequently used for construction. The development of gaps in stone walls need not result in their complete re-building for other materials, for example brick, can be employed to conceal small holes. Walls need not be constructed of freshly quarried stone, and in fact recycled material is relatively common in older walls. Such stones may be recognisable by their shape, or be of a geological type unlike the majority. The presence of paint or render traces will of course indicate reuse. Locally roadways were created from sandstone setts bedded in tar; stone cubes with a tarred face are easily recognised even when they find their way into walls. Wall patches of any of these materials may be mortared-in if they are created by unskilled masons. The use of mortar containing sand and modern Portland cement indicates work done within the last 75 years. Before that lime mortar with grey crushed ash in place of sand was utilised. The illustration shows a piece of worked stone fixed into a wall with modern mortar.
Because stone is so regularly recycled it is sensible to examine the constituent stones of walls for tool marks and other signs of working. I have seen many examples of partially dressed masonry which has clearly broken during the working process. Fragments of tombstones or querns also find their way into walling. It is important to distinguish signs of working from fossils. It appears that the old quarrymen believed that the presence of a fossil weakened the stone. Rocks containing fossils were not used for ashlar but tended to end up with the wallstone, as the coping stone below illustrates.
There are few things more difficult to date than a dry stone wall. At least they don’t seem to pre-date the Iron Age. In this period field walls consisted of large stones (orthostats) bedded in the ground; today remaining examples of these walls contain large gaps. Whether these gaps were originally filled with small stones, now removed, or hedges, or fence panels is not known. The orthostats resemble the shape of a dog’s tooth and may also be incorporated in later walls in an astonishing indication of the durability of boundaries. The Romans are thought to have introduced boundary hedges. Other Romano-British field boundaries are more likely to have been ditches. We pick up stone walls again with the ring garths of the Lakeland valleys, which are widely considered to be of Norse origin. Ring garths, or head dykes, were built round each valley to stop animals straying on to areas of cultivation. They formed a dividing line between fertile land on valley bottom and the coarse grazing on the fells. Clearly these walls were built by early settlers, perhaps Norsemen in the tenth or eleventh centuries. No other wall crosses a ring garth and other walls abut onto it. Medieval monasteries used stone walls for sheep granges in the north of England. More modern enclosure walls (and barns) date from the time of various enclosure acts of the late eighteenth and early nineteenth centuries. Enclosures were a massive stimulus to wall building.
Even if the creation of the wall is of unknown date there may be the incorporation of datable stones, for example Roman stones or worked masonry from a dissolved monastery. This gives a terminus post quem for the wall, but not the boundary it now represents. The date of such a boundary is not necessarily the same date as the wall that runs along it. Dry stone walls may be long established but still fall into disrepair if farms amalgamate, or be removed altogether to form larger fields. Walls do deteriorate and collapse over time, particularly on soft ground or steep slopes, and consequently need to have constant maintenance.