ARBOR LOW EXCAVATIONS IN I9OT AND 1902. 45 



delineated to follow the general slope of the ground, and not 

 to mark, in this part, every little depression or slight elevation 

 as it occurred. The contours of 6 inches vertical height 

 show the shape of the monument and its immediate surround- 

 ings within the " square."* The highest contour comes on the 

 top of the tumulus on the south-east rampart; the lowest, at 

 the north corner of the survey, a fall of 24A feet (7-47 m.) in 

 the ground from top to lowest part. 



The periphery of the crest of the rampart constitutes almost 

 a true circle, with a diameter of exactly 250 feet (76-2 m.), as 

 shown by the outer circle described on the plan. The centre 

 of the circle comes near the middle of the south-west side of 

 stone No. III. of the central group. (See black spot on 

 stone III., plan.) The crest of the vallum deviates very slightly 

 in any part from the true circle, excepting on the north-west, 

 where it bulges out. The bottom of the fosse, as seen on the 

 surface of the silting, declines from the line of the true circle 

 far more than the rampart, as shown by the inner circle described 

 on the plan, with a diameter of 190 feet (58 m.). The 

 only segment of this circle that can be said to be true is on 

 the south, south-west, and west. The ditch is thrown out far 

 more than the rampart to the north and north-west, but it would 

 not be expected to find that the fosse had silted up regularly 

 and symmetrically all round ; whereas the crest of the rampart, 

 of course, is much about in the same position as it was at the 

 age of construction. 



The ditch is marked by a depression from the original surface 

 all round averaging 5$ feet (i-68 m.), and it is surprising that 

 in the course of all these ages it should not have silted up 

 to a greater extent. 



The average height of the vallum above the general sur- 

 rounding turf-level, as shown by the contours, is, on the outside, 

 7 feet (2-13 m.); its height above the central plateau, about 

 6 feet (1-83 m.). The average vertical height from the crest 

 of the vallum to the surface of the silting of the fosse is 



* To ensure absolute precision, eighteen hundred levels were taken. 



