ON THE AGE OF STONE CIRCLES. 145 



The deposits of silting must now be described, beginning at the 

 bottom with the pure chalk rubble. The material was found, as in 

 the other cuttings, to cover the whole of the solid faces of the fosse, and 

 its accumulation must have been very rapid when the ditch fell into 

 neglect. Belies found in this deposit would probably all belong to the 

 first decade or so following the disuse of the monument. This silting 

 was no doubt the result of natural causes, i.e., the scaling of the profile 

 of the fosse in frosty and rainy weather, and the falling down of 

 material forming the embankment, which in all probability was not at 

 that time turf-clad. Comparatively small quantities of turf and mould 

 would, in the course of construction, be thrown up with the chalk to 

 form the great vallum, and the occasional fall of the dark mould from 

 the bank would be sufficient to account for the concave streaks, or 

 seams, in the chalk rubble of the fosse, which were even better defined 

 in the 1911 section than in the cuttings previously made. The lowest 

 seam of mould, which extended right across the cutting in one part, 

 reached at the point of greatest concavity to within five feet of the 

 bottom of the fosse. The three seams on the south side of the 

 silting were, for a length of several feet, exceptionally noticeable.'' 

 On the eastern margin the depth of chalk rubble in the middle of 

 the fosse was ten feet. This rubble was very large at about 2'5 feet 

 from the bottom, especially in the middle of the ditch, but it became 

 rather smaller again on the bottom. Pieces of iron pyrites were com- 

 monly found in the rubble, but very little flint was observed, and most 

 of the pieces were very small. Fragments of charcoal were occasionally 

 met with. At the top of this deposit the lumps of chalk were found 

 cemented together, no doubt by means of carbonate of lime contained 

 in water which had percolated through the upper silting, consolidating 

 the chalk and rendering it as durable as the hardest concrete. Its 

 thickness was perhaps hardly as great as in Cuttings I. and II. of 

 former years. 



The upper deposits of silling consisted, from the top downwards, as 

 in the other cuttings, of (1) turf and turf-mould, (2) surface silting, 

 (3) mixed silting, and (4) fine mixed silting, their thickness on the 

 eastern margin being, in the middle of the accumulation, 0'65, 3'35, 

 2'7, and 2 feet respectively. This gives a total depth of silting above 

 the chalk rubble of 8'7 feet. On the western margin, where the fosse 

 was shallower, these deposits were represented by a thickness of 

 7'7 feet. Dividing the surface silting from the mixed silting was a thin 

 seam of small pieces of chalk which was traced nearly, the whole way 

 along the cutting. So much has been said in the former reports on 

 these deposits that it will be unnecessary to make repetition here. 



Above the chalk rubble two distinct patches (not seams extending 

 across the cutting) of dark mould and very fine chalk were traced, the 

 lower one practically throughout the length of the digging. The higher 

 patch was at an average depth of 5 feet, the other about 7'2 feet, below 

 the surface, in what are called the ' mixed silting ' and the ' fine mixed 

 silting ' respectively. Maximum thickness of each, 0'6 foot. Evidence 



4 See similar seams of mould in the fosse of Wor Barrow, Handley, Dorset (Exca- 

 vations in Cranborne Chase, iv., plates 250, 251). 



1911. L 



