Where a mountain ridge stood in the path of a ley, the surveyor, instead of building a tump on the ridge as a sighting point, often cut a trench at the right angle and in the path of the ley. This shows as a notch against the sky and makes a most efficient sighting point from below. I have counted eight such artificial notches in the mountain ridge when on the road from Llanvihangel Crucorney to Longtown. Each notch can only be seen on the line of sight, and disappears when a quarter of a mile right or left. They are sometimes emphasised (as at Trewyn Camp) by an earth work thrown up on one side. The Wych on the Malvern ridge is an instance.
The two fine gaps near Flansford (Goodrich) and Marstow (Plate V.), both with bridges over them, are also ancient sighting cuttings.
The sighting cuttings were also used in passing over banks in lower ground. Cullis is one of the names for such an earth cutting, as Portcullis between Withington and Preston Wynne, and High Cullis above Gatley Park, recently visited by the Club.
There is a very neat example of such a cutting at Hungerstone, near Allensmore, where the cutting in the bank allows the ley to be sighted on to a pond on its way to the next tump, the one close to the church at Thruxton.
The word hunger (a common place-name element) indicates, I think, a cutting through a bank, not the bank itself, as now surmised. There are cuttings at most fords, which permit the water to be seen from above and serve as sighting points. The cutting near Charing Cross, which gives the name to the present Hungerford foot-bridge, probably came down through Inigo Jones' beautiful Water Gate.
Mr. Codrington in his book on Roman Roads describes the method used by Roman engineers "well known to surveyors for laying out a straight line between extreme points not visible from each other, from two or more intermediate points from which the extreme points are visible. By shifting the intermediate points alternately all are brought to lie in a straight line." This method was evidently used for all the leys.