by John Wright
In recent weeks I have been engaged in assessing the medieval and 17th Century water supply systems at Edinburgh Castle. It proved interesting in a number of ways. Initially I dowsed three deep wells, and by deep I mean a little in excess of 300 ft. Casting back through time to the 14th-15th Centuries, a further three wells were indicated. Much shallower, the second set came in at about 100 ft deep. Standard dowsing, when the question is clearly stated, is straight-forward. However, anomalies require working on. Why six wells, all six of which are now dry, in a comparatively small area? At this point some further knowledge is required.
Castle Hill, Edinburgh, is a basalt, volcanic from the dawn of time. Basalt is short on permeability and porosity. A below-ground (remote) dowsing sweep failed to throw up the presence of volcanic pipes where significant amounts of drainage or seepage might have collected. At this point I had doubts as to the validity of what my dowsing rod/rods were telling me.
A brief history of the castle emphasised the part played by water shortages in the castle’s early existence. I felt that I could safely assume that there had been an adequate supply at some time and so I started to extend my search for water round all the points of the compass. Because of the height of Castle Hill, the early wells could be disregarded. Water was dowsed a short distance to the north-west, at a depth below ground of just 26 ft.
From there on, details began to fall into place. A tunnel had been driven from the area presently located between the western end of Princes Street and the church or chapel located in the gardens. The tunnel was driven south-east and provided a conduited water supply to each of the three deep wells. The tunnel dimensions were/are 4 ft 4 ins x 4 ft 4 ins (the vast majority of medieval conduits are 3 ft 3 ins x 3ft 3 ins). The wells and the heading were dowsed as built in the 1620’s and provided a flow rate of 17 gallons per minute. Unfortunately, the aquifer from which the supply was taken lasted for less than one hundred years. I can pick up the self same, but much reduced aquifer at Moray Place, some 450 metres to the North.
One aspect of the above I haven’t followed up to its conclusion is where the tunnel ends. My initial dowsing survey failed to indicate the presence of water beneath the area extending from the Castle, east toward Hollyrood Palace. There is more information to be found. A challenge?
© 2001 John Wright & BSD EEG