288 DENUDATION OF THE LAND. Chap. VL 



six observations made at a distance of 10 yards 

 outside the embankment. The thickness of 

 the mould within two of the circular trenches 

 was measured every 5 yards all round, on the 

 inner sides near the bottom. My son Horace 

 protracted these measurements on paper ; and 

 though the curved line representing the thick- 

 ness of the mould was extremely irregular, yet 

 in both diagrams it could be seen to be thicker 

 on the north-eastern side than elsewhere. 

 When a mean of all the measurements in both 

 the trenches was laid down and the line 

 smoothed, it was obvious that the mould was 

 thickest in the quarter of the circle between 

 nortli-west and nortli-east ; and thinnest in 

 the quarter between south-east and south- 

 west, especially at this latter point. Besides 

 the foregoing measurements, six others were 

 taken near together in one of the circular 

 trenches, on the north-east side ; and the 

 mould here had a mean thickness of 2*29 

 inches ; while the mean of six other ijaeasure- 

 ments on the south-west side was only 1*46 

 inches. These observations indicate that the 

 castings had been blown by the south-west 

 winds from the circular enclosed space into 



