Oxford Book of Modern Science Writing by Dawkins Richard

Author:Dawkins, Richard [Richard, Dawkins,]
Language: eng
Format: epub
Published: 2010-10-16T02:29:40.000252+00:00

206 . WHO SCIENTISTS ARE

The uniform fi neness of the particles of which it is composed is one of its chief characteristic features.

Darwin argues that earthworms form vegetable mold by bringing ‘a large quantity of fi ne earth’ to the surface and depositing it there in the form of castings. (Worms continually pass soil through their intestinal canals, extract anything they can use for food, and ‘cast’ the rest; the rejected material is not feces but primarily soil particles, reduced in average size by trituration and with some organic matter removed.) The castings, originally spiral in form and composed of fi ne particles, are then disaggregated by wind and water, and spread out to form vegetable mold. ‘I was thus led to conclude,’ Darwin writes, ‘that all the vegetable mould over the whole country has passed many times through, and will again pass many times through, the intestinal canals of worms.’

The mold doesn’t continually thicken after its formation, for it is compacted by pressure into more solid layers a few inches below the surface. Darwin’s theme here is not directional alteration, but continuous change within apparent constancy. Vegetable mold is always the same, yet always changing. Each particle cycles through the system, beginning at the surface in a casting, spreading out, and then working its way down as worms deposit new castings above; but the mold itself is not altered.

It may retain the same thickness and character while all its particles cycle. Thus, a system that seems to us stable, perhaps even immutable, is maintained by constant turmoil. We who lack an appreciation of history and have so little feel for the aggregated importance of small but continuous change scarcely realize that the very ground is being swept from beneath our feet; it is alive and constantly churning.

Darwin uses two major types of arguments to convince us that worms form the vegetable mold. He fi rst proves that worms are suffi ciently numerous and widely spread in space and depth to do the job. He demonstrates ‘what a vast number of worms live unseen by us beneath our feet’—some 53,707 per acre (or 356 pounds of worms) in good British soil.

He then gathers evidence from informants throughout the world to argue that worms are far more widely distributed, and in a greater range of apparently unfavorable environments, than we usually imagine. He digs to see how deeply they extend into the soil, and cuts one in two at fi fty-fi ve inches, although others report worms at eight feet down or more.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.