144 REPORTS ON THE STATE OP SCIENCE. 



could not have been less than 55 feet — probably the largest dimension 

 of the sort obtainable in any prehistoric earthwork in Britain. 



Along the line of section on the eastern margin of the cutting a 

 narrow trench (3 feet wide) was dug from the south side of the cut- 

 ting towards the crest of the vallum, to ascertain the position of the 

 hewn chalk. It was found to run at an angle of 28° for a considerable 

 distance, at a depth of from l'l to 1'6 feet below the surface of the 

 turf. This digging was carried far enough to find clear traces of the 

 old turf line under the great vallum, and to reach the solid chalk at 

 a depth of about 2 - 2 feet below its surface. From this trench and the 

 level of the central plateau we were able to obtain a fairly accurate 

 estimate of the original depth of the fosse in this part, that is, its depth 

 below the ground level at the time of the construction of Avebury. This 

 estimate gives the depth of 31'5 feet for the fosse in the midlde, and a 

 height of about 16 feet for the vallum above the old surface line at 

 the present time; but the original height of the embankment, as 

 previously stated, was undoubtedly greater. 



At the close of the excavations we found that on the line of section 

 both the escarp and the counterscarp of the fosse, revealed by the 

 removal of all the silting, had faces inclined at different angles. The 

 following was the inclination of the solid chalk sides: — 



Escarp. — Lower 5 feet, inclination 90°; middle 18 feet, 62°; upper 

 part, 28°. 



Counterscarp. — Lower 8 feet, inclination 74°; middle 12 feet, 50°; 

 upper part, 28°. 



III. The Excavation of Catling VIII., Fosse. 



A length of 30 feet of fosse was excavated, but as a considerable 

 batter to the faces of the silting had to be left to avoid any risk of falls, 

 it was only possible to uncover completely a length of 21'5 feet of 

 the floor. Unlike the floor in the former cuttings, the bottom was 

 found to be very irregular and far from level. The fosse was deepest 

 along the eastern margin, viz., 18'7 feet below the surface of the silting. 

 It gradually rose as we continued the work of re-excavation westward. 

 The depths of the fosse below the surface of the silting along the 

 western margin of the cutting were 3 : Maximum, 1 6'8 feet; minimum 

 (in the south corner), 15'3 feet; in the middle of the fosse, 16'3 feet. 

 The maximum width of the bottom of the fosse was 15 feet at the east 

 end, and the minimum width in the middle about 9'5 feet. 



Two sectional diagrams of the floor were made, showing that the 

 levels taken varied to the extent of 2'95 feet, which was very surprising. 

 This may probably be accounted for by_ the poor quality of the rock, 

 which consisted of a soft, smooth, rotten, pale greenish-grey chalk of 

 the zone of Rhynchonella Cuvieri. (The common fossil, R. Cuvieri, 

 was found close to the floor.) This poor chalk occurred also in the 

 lowest part of the profile of the fosse, with occasional solid blocks of 

 whiter chalk projecting beyond it, as seen in some of the photographs. 



3 The turf level in the middle of the silting was five inches higher on the east margin 

 than on the west margin of the cutting. 



