WARPING, a mode of producing a deposition of the earthy matter which is suspended in rivers. This causes a stirring of the water, which prevents the finer particles from being deposited. It is only necessary to produce a stagnation of the water for a few hours to have a copious deposit, leaving the water clear over it On the low flats which border the mouths of rivers, occasional inun dations often cause a deposit which is highly fertilising. Thus the polders in Holland and Flanders have been formed of the mud of largo rivers, and, being drained and kept dry by dykes and sluices, have formed the most fertile soils.
Warping is an imitation of this natural process :—A bank of earth is raised along the course of the river, so high that the floods cannot pass over it. In some part of this dyke is a alnico for the double pur pose of letting in the water and letting it out at pleasure. When the tide is setting in and counteracting the natural current of the river, the sluice is opened and the water flows in by one or more channels made for the purpose of conveying it over the lower land, and covers it to the depth of high-water. The sluice is now shut, and the im prisoned water, becoming stagnant, deposits all the mud which it held suspended before. The sluice is opened at low-water, and the water is allowed to run out slowly ; it leaves a coating of mud or sediment, which hardens and dries rapidly. This operation is repeated until a thickness of several inches of new soil has thus been warped, when it is allowed to dry, and is then ploughed and cultivated like any other field. It takes some time before any corn will grow on the new warp : at first it looks like barren mud; but it soon dries to a better texture, and ultimately produces very extraordinary crops. If its fertility decrease, and its surface is still below high-water mark, a slight warping, like the inundations of the Nile, immediately restores the fertility. What is curious, is the almost total absence of organic
matter in the warp-soils, or rather, its intimate combination with time earths, so that it is not readily separated from them. It is neither like clay nor sand, but something between the two, soft to the touch, but not hardening into lumps when dry : neither very porous nor very retentive of moisture. The principal earth is silica, in a very fine state. It generally contains a portion of calcareous matter, probably from comminuted shells. It produces beans, oats, potatoes, and wheat in abundance, without any manure. It is admirably adapted to the growth of flax, especially when the warp is of a good depth.
The principal expense in warping is the sluice, and the canal through which the water is conducted over the land ; the longer this latter is, the slower the process, as much warp is deposited in the canal, which has sometimes to be dug out. Accurate levels must be taken, or much expense may be incurred uselessly, if the water will not cover the surface to a sufficient depth.
It is of little consequence what the soil was originally ; for a new soil is deposited over it. It should, however, not be too wet nor marshy : a porous soil is best, as this becomes the subsoil. All the inequalities which existed before, are obliterated by the warping, which fills up all cavities, and leaves a perfectly level surface. The fertility of warped land naturally leads to the conclusion that silica, in a very comminuted state, becomes best adapted for the roots of plants to shoot in, and to supply them regularly with the moisture necessary to their vegetation, and that their chief nourishment is derived from the atmosphere, since very little organic matter can be detected in warp, and few mineral substances besides the earths.