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Show 144 AMOUNT OF EARTII CHAP. III. these O'radually increased in numbers as the pastur: improved. In the year 1871 a trench was dug on the above slope, and the blades of grass were cut off close to the roots, so that the thickness of the turf and of the vegetable mould could be measured accurately. The turf was rather less than half ~n inch, and the mould, which did not contaul any st ones, 2"12" inches in thickness. •B enea• th this lay coarse clayey earth full .of :fhnts, bke that in any of the neighbounng ploughed fields. This coarse earth easily fell apart from the overlying mould when a spit ~as lifted up. The average rate of acc~mulatwn of the mould during the whole thuty years was only ·083 inch per year (i.e., nearly one inch in twelve years); but the rate must have been much slower at first, and afterwards considerably quicker. The transformation in the appearance of this field, which had been effected beneath my eyes, was afterwards rendered the more striking, when I examined in Knole Park a dense forest of lofty beech-trees, beneath which nothing grew. Here the ground was thickly strewed with large naked stones, and CrrAP. III. BROUGHT UP BY WORMS. 145 worm-castings were almost wholly absent. Obscure lines and irregularities on the surface indicated that the land had been cultivated some centuries ago. It is probable that a thick wood of young beech-trees sprung up so quickly, that tirno enough was not allowed for worms to cover up the stones with their castings, before the site became unfitted for their existence. .Anyhow the contrast between the state of the now miscalled "stony field," well stocked with worms, and the present state of the ground beneath the old beech-trees in Knole Park where worms appeared to be absent, was' striking. ..A. narrow path running across part of my lawn was paved in 1843 with small flagstones, set edgeways ; but worms threw up many castings and weeds grew thickly between them. During several years the path was weeded and swept; but ultimately the weeds and worn1s prevailed, and the gardener ceased to sweep, merely mowing off the weeds, as often as the lawn was mowed. The path soon became almost covered up, and after several years no trace of it was L |
