| OCR Text |
Show 272 DENUDATION OF THE LAND CHAP. VI. its castings, not in vermiform masses, but in little pellets of varying sizes: these are very numerous in some places, and Mr. Scott says that they "are washed away by every " shower." I was led to believe that a considerable quantity of fine earth is washed quite away from castings during rain, from the surfaces of old ones being often studded with coarse particles. Accordingly a little fine precipitated chalk, moistened with saliva or gumwater so as to be slightly viscid and of the ' . same consistence as a fresh cast1ng, was placed on the summits of s~veral castings .and gently mixed with them. These castmgs were then watered through a very fine rose, the drops from which were closer together than those of rain, but not nearly so large as those in a thunder-storm ; nor did they strike the ground with nearly so much .force as drops during heavy rain. .A_ casting thus treated subsided with surprising slowness, owing as I suppose to its viscidity. It did not flow bodily down the grass-covered surface of the lawn, which was here inclined at an angle of 16° 20'; nevertheless many par- CHAP. VI. AIDED BY WORMS. 273 ticles of the chalk were found three inches below the casting. The experiment was repeated on three other castings on different parts of the lawn, which sloped at 2° 30', 3° and 6o; and particles of chalk could be seen between 4 and 5 inches below the casting ; and after the surface had become dry, particles were found in two cases at a distance of 5 and 6 inches. Several other castinO's b with precipitated chalk placed on their su1nmits were left to the natural action of the rain. In one case, after rain which was not heavy, the casting was longitudinally streaked with white. In two other cases the surface of the ground was rendered somewhat white for a distance of one inch from the casting ; and some soil co1lected at a distance of 2-k inches, where the slope was 7°, effervesced slightly when placed in acid. After one or two weeks, the chalk was wholly or almost wholly washed away from all ihe castings on which it had been placed, and these l1ad recovered their natural colour. It may be here remarked that after very heavy rain shal~ow pools may be seen on lev~l or nearly level fields, · where the soil is not T |
