The rippled stalks are tied in small bundles and packed, roots downwards, in the dams till they are quite full; over the top of the upper layer is placed a stratum of rushes and straw, or sods with the grassy side downwards, and above all stones of sufficient weight to keep the flax submerged.
The heathlands when sufficiently drained are prepared for cultivation by being cut into sods and burnt.
Thirdly, nowhere very clear on the surface and as yet detected only at a few points, there are the remains of the " turf wall," constructed of sods laid in regular courses, with a ditch in front.
An ancient writer states that the rampart was built of regularly laid sods (the same method which had probably been employed by Hadrian), and excavations in 1891-1893 have verified the statement.
Just sufficient to effectually damage the roots of the plants forming the sward and then, after drying the sods and burning them, spreading the charred material and ashes over the land.