Tide-mills: the locational factors
The location of any water-powered mill is dictated by the landscape and the hydrological factors. The particular factors that facilitate or prevent the creation of a tide-mill can be postulated by a study of the locations of known tide-mills. (Minchinton 1971.) These appear to be the relevant features.
- The tidal range in the British Isles is in theory sufficient to provide good water-power for a tide-mill anywhere on the coast line although the tidal range is particularly large in the West Country and therefore particularly suited to tide-mills.
- It was not then possible to establish a tide-mill in a situation that is open to the sea. It is usually not economically or practically feasible to enclose a millpond in such circumstances. Even if it were possible the building and its dams would be susceptible to damage by the full force of the sea and would be rapidly destroyed. There are therefore long parts of the coastline that are not suitable for the construction of tide-mills whatever the tidal range, and where no tide-mills are known.
- Almost all tide-mills are in sheltered water in estuaries, usually on creeks or inlets of small river valleys flowing into a larger estuary. The concentration of tide-mills around estuaries is clearly shown on the maps prepared by Minchinton. In Devon and Cornwall they are strongly clustered around the estuaries in the vicinities of Falmouth and Plymouth.
- A common location for tide-mills is in a partly naturally enclosed body of usually shallow water that can be formed into a millpond by the construction of a dam as short as possible.
- The soil under the mill pond, and surrounding land enclosing it, must be impervious, or nearly so, and covered by water for the great majority of the tidal range.
- The mill pond must be of a certain size to be economically viable. Mill ponds were sometimes as small as one acre (about 4,000m2). Some were as large as 30 acres (about 12ha). The gross usable power is however directly proportional to the size of the mill pond (if the tidal range is the same) and it is theoretically possible to relate the surface area of the mill ponds to the number of mill wheels and pairs of stones that can be operated from it. Such calculations are not shown here. Using very sparse anecdotal evidence it seems that it requires one or two acres of mill pond to provide enough power for each pair of stones.
Perhaps the above factors are incomplete or need refinement. But nevertheless we can safely conclude that there were only a limited number of locations suitable for tide-mills around the English coast, and that parts of Devon and Cornwall were particularly well supplied with such sites.
(For the purpose of this paper, tide-mills are those where almost all the power comes from the impounding of the tide although most tide-mill ponds will have some fresh water flowing into them.)
Matching Later tide-mills in Cornwall and Devon with Domesday listings
There were 19 tide-mills dated from the 17th century onwards in Cornwall identified by Professor Minchinton which were listed by him in 1971 as in Table 2 below.
This list may be compared with only six Cornish mills listed in Domesday as Table 3 below.
There are two points to note. Firstly none of the names of the five Domesday vills with mills listed therein apparently matches any of the locations of the later tide-mills in Table 2 above. Secondly the Domesday vills with listed mills do not appear to be in locations in which tide-mills could have been constructed (being nowhere near the sea) but they would have been suitable for fresh-water mills. This is certainly so for four of the locations, which are all inland. But for one of them the case is less clear. Connerton is not so far from the sea, although the nearest coastline does not appear particularly suitable for the construction of tide-mills. Nevertheless Hayle Mill is not far away and the possibility cannot be ruled out that Connerton in Gwithian held a mill or rights in a mill outside its boundaries at Hayle.
But generally at face value these facts are consistent with the theory that tide-mills were not listed in the Cornwall Domesday survey.
The pattern is repeated in Devon although interpretation is more complex because more Domesday mills are listed in the County. There are entries in 78 locations and 96 mills. Therefore the analysis for this County starts with the 12 known tide-mills and attempts to match those locations with the Domesday entries, and then looks to see if mills are listed in them. Minchinton’s list is used as in Table 4 below.
Six of those ten locations can be readily matched with Domesday vills of the same name: Topsham, Totnes (with three Domesday entries), Blaxton, Bideford, and Instow. None of them have a Domesday mill listed. The Plymouth parishes were previously, Devonport, East Stonehouse, Plympton and Plymstock, including the ancient parishes of Plymouth Saint Andrew, Stoke Damerel, East Stonehouse, Saint Budeaux, Eggbuckland, Tamerton Foliot, Plympton Saint Maurice, Plympton Saint Mary and Plymstock. None of these or the surrounding parishes have Domesday mills recorded in them. None of the Domesday locations around Dartmouth list any Domesday mills. During this search it has not so far been possible to find any tide-mill locations in Devon that definitely correspond with a Domesday listing.
The pattern might be repeated elsewhere. In Dorset Professor Minchinton lists two tide-mills, Melcombe and Weymouth. Neither Domesday vill has a Domesday Mill recorded.
At first sight these facts might support the thesis that the Domesday Survey does not list tide-mills, at least in these Western Counties.
The above evidence needs to be interpreted with caution. There are good grounds to suppose that some assets, such as mills and saltpans and even woodland in a few cases, were not always physically located in the Domesday vill in which they are recorded. However this point would not seem to invalidate the general contention.
Why did the Domesday survey not record tide-mills?
If the thesis is correct it may be that we will never know the exact reasons why Domesday does not record tide-mills. It is possible to make a conjecture. For salt water mills the dams enclosing the water, and therefore the source of the power for the tide-mill, was by its nature below the high water mark. It might have been that neither the King, nor his tenants in chief, considered that they owned the sea or the seabed. Perhaps they did not lay claim to the area between the high water mark and low water. If that was the case it might have been thought that it was not then possible to draw rent from it or tax the power of the sea. (It should be noted in passing that there are many other valuable real estate assets that existed in 1086 which were not listed in the Domesday survey.)
There are immediately strong grounds for questioning this conjecture. There are many coastal salt works recorded in Domesday. In the Devon and Cornwall vills they are listed, for instance, in Blaxton and Ashprington. These coastal salt-pans must have been below the high water mark using the tidal sea bed in much the same way as a mill pond for a tide-mill. Why then should saltpans and salt water mills be treated differently in Domesday?
(The law of the seabed developed differently in later ages. By the 18th century the Crown, in the guise of the Crown Estate, owned the seabed below the high water mark. This is still the case today. It is now administered and managed under the Crown Estate Act 1962 through the Crown Estate Commissioners.)