Silt

“ The relative position in the silt, from which the canoes were exhumed, could help us little in any attempt to ascertain their relative ages, unless they had been found vertically above each other. The varying depths of an estuary, its banks of silt and sand, the set of its currents, and the influence of its tides in scouring out alluvium from some parts of its bottom and redepositing it in others, are circumstances which require to be taken into account in all such calculations. ”

“ Silt consists of the soil particles which are finer than sand,—too small in fact to be felt as soil grains by rubbing between the fingers, and yet it is distinctly granular, while clay is a mere plastic or sticky mass like dough. What are commonly called clay soils consist largely of silt, but contain enough true clay to bind the silt into a stiff mass. In the main such soils are silt loams, but when deficient in organic matter they are yellow in color as a rule, and all such material is usually called clay by the farmers. ”

“ Evaporation to dryness with a solution of magenta will often impart a color to the clay particles which is not removed by subsequent suspension in water. The harder and larger silt particles are not easily stained, especially if they be firm and undecomposed. ”

“ The excessively fine texture of clay opposes great frictional resistance to the movement of the water, and the same is true of the finest silts, which, like clay, remain almost indefinitely suspended in water. But it must be remembered that while pure grains of silt will in wetting remain unchanged in size, clay particles, and the clay incrusting silt grains, will on wetting swell greatly, and thus fill up the interstices, largely closing them up against the passage of water. ”

“ Some deposit of silt generally occurs. The construction of an embankment reduces the area of the flood water, and thus generally reduces the silting and leaves more silt in the river proper. The depth and velocity in the river are increased. Everything depends on which is increased most. Most likely the stream is of shallow section and the velocity is increased most (Chap. IV., Art. 6, par. 6) , and the increased silt-supporting power may make up for the increased charge of silt. ”

“ Silt accumulates in docks where the lowering of the water-level by locking, the drawing down of half-tide basins, and the raising of the water at spring tides, involve the admission of considerable volumes of tidal water heavily charged with silt, which is deposited in still water and has to be periodically Maintenance of depth.removed by dredging. ”

“ The water coming up with the tide is heavily charged with mud washed from the Humber banks, and this silt is deposited to the depth of some feet in places, and has always proved to be of the utmost fertility. ”

“ The formation of shales will now demand our attention. When a river is carrying down with it a quantity of mud or clay, it is transported as a fine, dusty silt, and when present in quantities, gives the muddy tint to the water which is so noticeable. We can very well see how that silt will be carried down in greater quantities than sand, since nearly all rivers in some part of their course will travel through a clayey district, and finely-divided clay, being of a very light nature, will be carried forward whenever a river passes over such a district. ”

“ If silt-basins have been placed at those points at which the fall diminishes, the obstruction will usually be found to occur at the outlets of these, from a piling up of the silt in front of them, and to extend only a short distance below and above. It is not necessary to take up the tiles until they are found to be entirely clean, for, if they are only one-half or one-third full, they will probably be washed clean by the rush of water, when that which is accumulated above is tapped. ”

“ Whatever water runs off from a field carries with it great quantities of mud and fine silt, together with the most precious elements of fertility. These elements are the soluble alkaline salts and organic manner which are readily taken up by the water, and once removed are not speedily restored. ”

“ The tremendous force of its current, and the volume of its waters bring down immense masses of silt annually. Beginning at a point near the capital, wide sand-banks are formed, which are bare at low water, but are flooded in time of rain, or at the melting of the spring snows. ”

“ The wash of the hills and mountain-sides carries with it into the streams tons and tons of silt to fill up the dams and beds of the streams, as well as working irreparable injury to the comparatively thin soil covering the mountains. ”

“ The tendency of the bed to silt will (Art. 6) be greater at the deeper section and, when silting has occurred on the bed, the section will be reduced and there will be a tendency to scour at the sides. Thus the cross-sections tend to become also uniform in shape. If a bank of silt has formed in a stream, the tendency is for scour to occur. There is also a tendency for silt to deposit just below the point where the bank ends. Hence a silt bank often moves downstream. ”

“ The average-constituted small boy, who throws stones by nature, discovers something lacking in the scheme of creation as applied to these districts. Everywhere the soil is composed of the ancient alluvial silt brought down to these levels by those lazy streams, the Nene, the Lark, the Cam, and the Ouse, and of the dried peat of these sometime stagnant and festering morasses. ”

“ The particles broken off make grains of sand, or, if very fine, particles of silt or mud. Even after a stone has been rounded it is subject to further wear and reduction, and in the course of time may be literally worn out. ”

“ It became more curious still when, three weeks afterwards, the unrecognisable body of a man was found half buried in the silt left in the alluvial basin by the subsiding floods--a man of more than middle age, whose right hand was clenched tight, over nothing. ”

“ Etym., silex, which see, A siliceous rock is one mainly composed of silex.
Silicified. Any substance that is petrified or mineralized by siliceous earth.
Silt. The more comminuted sand, clay, and earth, which is transported by running water. It is often accumulated by currents in banks. Thus we speak of the mouth of a river being silted up when its entrance into the sea is impeded by such accumulation of loose materials.
Simple mineral. Individual mineral substances, as distinguished from rocks, which last are usually an aggregation of simple minerals. ”

“ In their journey these materials rub against each other and against the banks and bed of the stream, thereby undergoing a prolonged process of grinding whereby the softer rocks are reduced to very fine sand and silt which becomes, in time, very intimately mixed with the clay. ”

“ By washing the grosser impurities from the clay mud through a process in which the heavier particles settled, leaving the silt or finer clay to be poured off, some artist of a very early time found a material that became one of his most valuable helps in adding to the furnishings of his tribal household. ”

“ Hence, the deposits in lakes (lacustrine) and at the mouths of rivers (estuarine) increase more or less regularly in fineness according to their distance from the point at which the water enters, the gravel and stones being deposited first, then the coarse sand, next the finer sand and finally the silt and clay [91] (fig. 14) . ”

“ Now put some soil into A. At once the soil is stirred up, the water becomes muddy, and the muddy liquid flows into B. But very soon a change sets in, the liquid in A becomes clear, and only the grit and stones are left in the bottom: all the mud—the clay and the silt—is washed into B. There it stops for a long time, and some of it will never wash out. The liquid flowing into C is clearer than that flowing into B. If you keep on putting fresh portions of soil into A you can keep B always muddy, although A is usually clear. ”

“ Humusless soils that are mixtures of sand, silt, and clay can become extremely compacted and airless because the smaller silt and clay particles sift between the larger sand bits and densely fill all the pore spaces. These soils can also form very hard crusts that resist the infiltration of air, rain, or irrigation water and prevent the emergence of seedlings. Surface crusts form exactly the same way that concrete is finished. ”

“ In increasing the fall, curves in the grade are always advisable, in decreasing it they are always objectionable, except when the decreased fall is still considerable,—say, at least 2 feet in 100 feet. The reason for making an absolute angle at the point of depression is, that it enables us to catch the silt at that point in a silt basin, from which it may be removed as occasion requires. ”

“ While your soil contains eight hundred pounds of nitrogen on the steeper slopes and one thousand pounds on the more gently undulating areas, ours contains five thousand pounds in the brown silt loam and eight thousand pounds in the heavier black clay loam. ”

“ We find, in fact, that most of the tenants of the water, particularly the forms which dwell upon the bottom, are provided with an array of contrivances which enable them to clear away from their bodies such small quantities of silt as may inconvenience them. ”

“ Dredging is not practicable, as the river frequently deposits as much as fifteen feet of silt in one place in the course of a single year, and as frequently removes it in the course of a single week or less. The quality of the soil itself also makes diking and revetting peculiarly difficult. ”

“ Every intelligent conservationist, whether farmer, business man or student, observes that over the country-wide the soils are being impoverished by the wash of surface waters, and the fertile lands are being carried away to enrich the sea. If we seek figures again, we are told that one and one-quarter billion tons of silt are deposited annually in the Mississippi River, one half of which serves to impede navigation and the other half to extend the state of Louisiana out into the Gulf of Mexico. ”

“ If a soil be cemented together into a homogeneous mass, its porosity sinks to a minimum; if it be composed, however, of numerous fine particles, each preserving its own physical condition, the porosity of the soil will rise to a maximum. The porosity of a soil may be judged very closely by the percentage of fine particles it yields by the process of silt analysis to be described further on. In general, the more finely divided the particles of a soil, the greater its fertility. ”

“ The sediments of the past are many
miles in collective thickness: yet the feeble silt of the rivers
built them all from base to summit. ”

“ It is evident that the methods of separation and examination from a mineralogical point of view about to be described can only be applied to silts of the largest size. The finer silts can not be separated into portions of different specific gravities by separating liquids of varying densities on account of the slowness with which they subside, thus tending to adhere to the sides of the separating vessels and to form floccules which are not all composed of the same kind of mineral particles. ”

“ Should sand be in excess, the soil is impoverished, since silica contains no nutriment, and it is rendered too dry, as on account of the relatively small surface of the sand grains in proportion to their mass it retains but little water. ”

“ Etym., German schalen, to peal, to split.
Shell mar. A deposit of clay, peat, and other substances mixed with shells, which collects at the bottom of lakes.
Shingle. The loose and completely water-worn gravel on the sea-shore.
Silex. The name of one of the pure earths, being the Latin word for flint, which is wholly composed of that earth. French geologists have applied it as a generic name for all minerals composed entirely of that earth, of which there are many of different external forms.
Silica. One of the pure earths. Etym., silex, flint, because found in that mineral. ”

“ Wherever the top of the slate beds, and the soil upon it, is laid bare, the black layers of slate may be seen gradually melting—if I may use the word—under the influence of rain and frost, into a rich tenacious clay, which is now not black, like its parent slate, but red, from the oxidation of the iron which it contains. ”

“ The marks made by the implements employed in hewing the rock are always distinctly recognisable. Moreover within, sunk in the floor, are silos for the storage of grain, the soil often somewhat higher about their orifices than elsewhere, and sometimes provided with covers. ”

“ They have a saying out here that soil is as rich as it is sticky. If this is true Dinky-Dunk has a second Garden of Eden. This mud sticks to everything, to feet, to clothes, to wagon-wheels. But there's getting to be real warmth in the sun that shines through my window. ”

“ At Paraetonium, and on the road to Ammon, and at Casius in Egypt there are marshy lakes which are so salt that they have a crust of salt on the surface. In many other places there are springs and rivers and lakes which are necessarily rendered salt because they run through salt pits.
8. Others flow through such greasy veins of soil that they are overspread with oil when they burst out as springs: for example, at Soli, a town in Cilicia, the river named Liparis, in which swimmers or bathers get anointed merely by the water. ”

“ Everything is of solid salt, except where some insecure roof is supported by huge timbers or a wooden bridge is thrown over some vast chasm. As depth is attained the air grows drier and purer, and the points and faces of the rock become more crystalline and beautiful. ”

“ Ruskin reminds us that the filthy mud from the street of a manufacturing town is composed of clay, sand, soot and water; that the clay may be purified into the radiance of the sapphire; that the sand may be developed into the beauty of the opal ”

“ The highest and most extensive mountain ranges are huge masses of silica, and the deserts of Africa and Asia are vast plains of the same abundant substance. Silica forms the sand and shingle of the sea-shore, and enters into the composition of every soil; it is the chief ingredient of some of our most precious jewels ”