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Show 256 DISINTEGRA1'ION CHAP. v. them appeared a little worn, thoug~ not rounded. Notwithstanding the e cases, If we consider the evidence above given, there can be little doubt that the fragment 'which serve as mill tones in the gizzards of worms, suffer, when of a not very hard texture, sorne amount f attrition. and that the smaller particles in 0 ' d . the earth, which is habitually swallowe In such astonishingly large quantities by worms, are ground together and are thus .le~iga;,ed. If this be the case, the "terra tenmssnna, the "pate cxcessivemout fine,"-of which tho castina-s lara-ely consist, is in part due to the mecha5n ical 5 action of the gi~zard; * an d t h' 18 :fine matter, as we shall see in the next chapter, is that which is chiefly washed away from the innumerable castings on every field during each heavy shower of rain. If the softer stones yield _at . all, the harder ones will suffer some slight amount of wear and tear. * 1'his conclusion reminds me of tho vast amount of extremely fine chalky mud which is found within tho lagoo n~ of many atolls where the sea is tranqnil and waves cannot tnturatc tho block~ of coral. This mu l mu t, as 1 believe(' The Stl11ctm.·c and Distribution of Coral-Reefs,' 2nd edit. 1874:, p. 19), b~ attnbutctl to tho innumerable annelills and other anim:tl~ whJCh bun·?w jnto the dend coral, aml lo the fishes, Holothunam;, &c., whwh browse on the living corals. CIIAP. v. AND DENUDATION. 257 The trituration of small particles of stone in the gizzards of worms is of more importance under a geological point of view than may at first appear to be the case; for Mr. Sorby has clearly shown that the ordinary means of disintegration, namely, running· water and the waves of the sea, act with less and less power on fragments of rock the smaller they are. "Hence," as he remarks, "even making no allowance for the extra "buoying up of very minute particles by a "current of water, depending on surface " cohesion, the effects of wearing on the form " of the grains must vary directly as their "diameter or thereabouts. If so, a grain 1 " of an inch in diameter would be worn ten "times as much as one rh of an inch in ''diameter, and at least a hundred times as "much as one T 1 00 of an inch in diameter. "Perhaps, then, we may conclude that a " grain -f~ of an inch in diameter would be "worn as much or more in drifting a mile as "a grain 10\-o- of an inch in being drifted " 100 miles. On the same principle a pebble " one inch in diameter would be worn re- ,, latively more by being drifted only a few s |