258 DISINTEGBATION CHAP. V. 



overlying the buried tesselated pavement, 

 through which worm-burrows passed ; and 

 these castings contained innumerable particles 

 of tiles and bricks, of concrete and cement, 

 the majority of which had manifestly under- 

 gone some or much attrition. There were 

 also many minute flakes of a micaceous slate, 

 the points of which were rounded. If the above 

 supposition, that in all these cases the same 

 minute fragments have passed several times 

 through the gizzards of worms, be rejected, 

 notwithstanding its inherent probability, we 

 must then assume that in all the above cases 

 the many rounded fragments found in the 

 castings had all accidentally undergone much 

 attrition before they were swallowed ; and 

 this is highly improbable. 



On the other hand it must be stated that 

 fragments of ornamental tiles, somewhat 

 harder than common tiles or bricks, which 

 had been swallowed only once by worms kept 

 in confinement, were with the doubtful ex- 

 ception of one or two of the smallest grains, 

 not at all rounded. Nevertheless some of 

 them appeared a little worn, though not 

 rounded. Notwithstanding these cases, if we 



