CHAP. VI. CASTINGS BLOWN TO LEEWARD. 291 



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- 

 north-west and north-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 measure- 

 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 



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