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Show 304 DENUDATION OF THE LAND. CHAP. VI. worm-castinO's, is washed down, and accumulates in the lower parts, notwithstanding the percolation of an unknown quantity into the underlying chalk; a supply of ~resh ~arthy matter being afforded by the d1ssolutwn of the chalk through atmospheric and other agencies. 305 ) CHAPTER VII. CONCLUSION. Summary of tho part which worms have pln.yccl in the hi~Lory of tho world-Their aid in tho disintegration of rocks-! n tho denudation of the Iand-In tho pre ·ervation of ancient remains -In the preparation of tbc soil lor the growth of plantsMental power~:; of worms- Concln~ion. WoRMS have played a more important part in the history of the world than most persons would at first suppose. In almost all humid countries they are extraordinarily numerous, and for their size possess great muscular power. In many parts of England a weight of more than ten tons ( 10,51 () kilogrammes) of dry earth annually passes through their bodies and is brought to the surface on each acre of land; so that the whole superficial bed of vegetable mould passes through their bodies in the course of every few year~. From the collapsing of the old burrows the mould is in constant though slow movement, X |
