CHAP. IV. OF ANCIENT BUILDINGS. 197 



so about six months before. My son collected 

 all from one of the holes, the area of which 

 was 5-32 square feet, and they weighed 7*97 

 ounces. Assuming that this amount had 

 accumulated in six months, the accumulation 

 during a year on a square yard would be 

 1*68 pounds, which, though a large amount, 

 is very small compared with what, as we 

 have seen, is often ejected on fields and 

 commons. When I visited the abbey on 

 June 22, 1877, the old man said that he had 

 cleared out the holes about a month before, 

 but a good many castings had since been 

 ejected. I suspect that he imagined that he 

 swept the pavements oftener than he really 

 did, for the conditions were in several re- 

 spects very unfavourable for the accumulation 

 of even a moderate amount of castings. The 

 tiles are rather large, viz., about 5i inches 

 square, and the mortar between them was in 

 most places sound, so that the worms were 

 able to bring up earth from below only at 

 certain points. The tiles rested on a bed of 

 concrete, and the castings in consequence con- 

 sisted in large part (viz., in the proportion 

 of 19 to 33) of particles of mortar, grains of 



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