OCR Text |
Show 274 DENUDATION OF TIIE LAND CHAP. VI. very porous, and the water in them is often slightly muddy; when such little pools have dried the leaves and blades of grass at their bottom' s are generally coated with a thin layer of mud. This mud I believe is deri vocl in large part from recently ejected castings. Dr. King informs me that the majority of the before described gigantic castings, which he found on a fully exposed, bare, gravelly knoll on the Nilgiri Mountains in India, had been more or less weathered by the previous north-east monsoon ; and most of thmn presented a subsided appearance. The worms here eject their castings only during the rainy season ; and at the time of Dr. King's visit no rain had fallen for 110 days. l-Ie carefully examined the ground between the plaoo where these huge castings lay, and a little water-course at the base of the knoll, and nowhere was there any accumulation of fine earth, such as would necessarily have been left by the disintegration of the castings if they bad not been wholly removed. He therefore bas no hesitation in asserting that the whole of th<::se huge castings are annually washed during the two monsoons (when CHAP. VI. AIDED BY "WORMS. 275 about 100 inches of rain fall) into the little water-course, and . thence into the plains lying below at a depth of 3000 or 4000 feet. Castings ejected before or during dry weather become hard, sometimes surprisingly hard, from the particles of earth havino- Leou b cemented together by the intestinal secre-tions. Frost seems to be less effective in their disintegration than might have been expected. Nevertheless they readily disintegrate into small pellets, after being alternately moistened with rain and again dried. Those which have flowed during rain down a slope, disintegrate in the same manner. Such pellets often roll a little down any slopinosurface; their descent being sometimes muc~ aided by the wind. The whole bottom of a broad dry ditch in my grounds, where there were very .few fresh castings, was completely covered With these pellets or disinteo-rate l . b castings, which had rolled down the steep sides, inclined at an angle of 27°. ~ear Ni.ce, in places where the great cylindncal castings, previously described, abound, the soil consists of very fine arenaceo-calcareous loam; and Dr. King infonns me that T 2 |