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Show 254 DISINrrEGRATION CIIAP. v. was impossible to look at with the naked eye or throuO'h a stronO' lens, and doubt for a b b moment that they had almost all undergone much attrition. I speak thus after having examined small water-worn pebb1es, formed from Roman bricks, which M. :Henri de Saussure had the kindness to send me, and which he had extracted frmn sand and gravel beds, deposited on the shores of the Lake of Geneva, at a former period when the water stood at about two metres above its pre ent level. The sn1allest of these .water-worn pebbles of brick from Geneva resembled closely many of those extracted from the gizzards of worms, but the larger ones were somewhat smoother. Four castings found on the recently uncovered, tesselated floor of the great room in the Roman villa at Brading, contained many particles of tile or brick, of mortar, and of hard white cement; and the majority of these appeared plainly worn. The particles of mortar, however, seemed to have suffer d more corrosion than attrition, for grains of silex often projected from their surf~tees. Castings from within the nave of Beaulieu CrrAP. V. A;ND DENUDATION. 255 .Abbey, which was destroyed by Henry VIII., were collected from a level expanse of turf, 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 undergone 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 ca es 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 fi·agments 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 exception of one or two of the smallest grains, not at all rounded. Nevertheless some of |