Chap. V. AND DENUDATION. 255 



were innumerable castings. Some of them 

 were coloured of a uniform red owing to 

 the presence of much brick-dust, and they 

 contained many particles of brick and of 

 hard mortar from 1 to 3 mm. in diameter, 

 most of which were plainly rounded; but 

 all these particles may have been rounded 

 before they were protected by the turf and 

 were swallowed, like those on the bare parts 

 of the road which were much worn. A hole 

 in a pasture-field had been filled up with 

 brick-rubbish at the same time, viz., seven 

 years ago, and was now covered with turf; 

 and here the castings contained very many 

 particles of brick, all more or less rounded ; 

 and this brick-rubbish, after being shot into 

 the hole, could not have undergone any 

 attrition. Again, old bricks very little 

 broken, together with fragments of mortar, 

 were laid down to form walks, and were 

 then covered with from 4 to 6 inches of 

 gravel; six little fragments of brick were 

 extracted from castings collected on these 

 walks, three of which were plainly worn. 

 There were also very many particles of hard 

 mortar, about half of which were well 



