. A treatise on rocks, rock-weathering and soils;. Petrology; Soils. 302 THE EEGOLITH material in situ, though differing radically in both composition and origin from those just described, are those portions of the regolith which result from the gradual accumulation of organic matter with only small amounts of foreign detritus; which are made up almost wholly of the combined accumulations, organic and inorganic, of growing plants. Such may be found in all stages of formation, in enclosed ponds or lakes, without appre- ciable inlet or outlet, being merely due to standing water in low places. '
. A treatise on rocks, rock-weathering and soils;. Petrology; Soils. 302 THE EEGOLITH material in situ, though differing radically in both composition and origin from those just described, are those portions of the regolith which result from the gradual accumulation of organic matter with only small amounts of foreign detritus; which are made up almost wholly of the combined accumulations, organic and inorganic, of growing plants. Such may be found in all stages of formation, in enclosed ponds or lakes, without appre- ciable inlet or outlet, being merely due to standing water in low places. ' * Such pools, when not exposed to periodical drying up, are invaded by a peculiar vegetation, first mostly composed of conferva, simple thread-like plants of various color and of prodi- gious activity of growth, mixed with a mass of infusoria, animal- cules, and microscopic plants, which, partly decomposed, partly containing the floating vegetation, soon fill the basins and cover the bottom with a coating of clay-like mould. So rapid is the work of these minute beings, that in some cases from 6 to 10 inches of this mud is deposited in one year. Some artificial basins in the large ornamental parks of Europe have to be cleaned of such muddy deposits of floating plants, mixed with small shells, every three or four years. '*When left undisturbed, this mud becomes gradually thick and solid; in some cases, of great thickness; affording a kind of soil for marsh plants, which root at the bottom of the basins or swamps and send off their stems and leaves to the surface of the water or above it, where their substance becomes in the sunshine hard and woody. '*As these plants periodically decay, their remains of course drop to the bottom of the water; and each year the process is repeated, with a more or less marked variation in the species of the plants. After a time the basins become filled by these. Fig. 30.—Section across a small lake, a, bed rock; td, drift; cc, growing peat; dd, de
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectpetrolo, bookyear1913
