SOILS OF ORGANIC ORIGIN.

North Otago Times, Volume XXVIII, Issue 3970, 2 June 1885, Page 4

SOILS OF ORGANIC ORIGIN.

{Farmers Magazine. ) m I These are plant and animal formation!, the former comprising vegetable mould - tnd . pfe»t mosses ; the latter, beds of chhlk and limestone, ocean clay, &c. / Vegetable mould is as widespread a§ vegetation. ]t forms everywhere that plants grow, and is the foundation, if not as of'en tbe entire source, of the organic .portion of the soil. Where vegetation ia scanty, or where tbe produce of the soil id removed by man or animals, it occurs sparingly. Deep beds of thii mould arc, however, met with in the foresti, unde; trees, and on dry land generally wherever. Tegetation is rank or neglected. Peat Mosses— Like vegetable mould, these deposits are p oduced by tbe slow decay of plants and their remains. There it this difference in their origin, however •—mould forma on dry land, peat forim, only under water. The peat may arise, simply from the accumulation ol neglected vegetable matter in moist situation! "Where successive generations of plants have grown and decayed upon a soil, the ve!/eta''le matter inceasea in such a pro portion thxt the noil approaches to a peat in iti nature ; and if in a situation where it can receive water from a bigher district, it btcomea sponcy and unfitted for the growth of the finer varieties of plauts. Another mode in which peat i« formed ia , by the gradual accumulation and decomposition of aquatic plants in ihallow lakes and ttagnant pools. This kind of peat is of a more loose < and apongy quality. What hai greatly contributed to the growth of this kind of peat is the destruction of anoient forenta,. either by the operation of some natural cause or by the hand of man. When water gets collected or choked vp — in a mora?s, for, imtance an active vegetation soon hegins to form a peat or vegetable soil, and the depth of the bog is only determined by the level or height of oveiflow of water from it. Many plants contrive to grow in this, and by gradual decay from peat ; especially the bog moss, sphagnum, which while it grows above decays beneath. There are some extensive peat bogs or motnea in the British Islands, and they are said to cover a tenth of the surface of Ireland. T ese formations would appear to belong to a time when the rainfall was probably greater than it is now ; for the peat, as a rule, is now no longer growing. Oialk is a deep sea deposit, formed by the calcareous parts of fish, corals, zoopbytei, and animalcule ; the siiicious ports of these organisms being the origin of the flints so abundant in this formation. Limestones, with the exception of a few fresh water travertint are all of the lame origin as chalk. They are derived from the head parts of marine organism*, the shells of foraminiferrc, and molluscs, &c. Ocean Clay. — It seems evident from the observations recorded by Sir William Tbomsou from the Challenger expedition, that clay, which we have hitherto looked upon n» e«oentialiy the product of the dis ineura iou of older rocks, may be under Certain circumstances an orgnnic formation like cltxlW, and that, as a matter of fact, an area of v»st extent on the surface of the globe is being covered by such a deposit at the prestnt day. The deep sea observations taken during the Challenger expedi tion go to prove that wherever the depth increases from about 2,200 to 2,000 fathoms, the modern chalk formation of the Atlantic and other oceans passes into fl cay. In this clay no loraminifertc can be detected. All evidence on the subject, ho«e»er, peem* to show that foramin'teroc had le n p-<s.>nt in these clays, but that thtir crtlcenoui sheila hal been dissolved out of them ; this being aff.:ct"d through tne agency of water con:ninin£ carbonic acid at an early stage of the formation ot these deposit*.