Groundling

“ Raindrops hung on the copper wire like a string of pearls, and the heavy clay of the fields was scooped and moulded by the rain into little saucer-like depressions as if by a potter's thumb. Behind us lay the reserve trenches, their clay walls shored up with wickerwork, and their outskirts fringed with barbed wire whose intricate and volatile coils looked like thistledown. [Pg 61] The village behind whose walls we now sheltered lay in a No Man's Land between the enemy's lines and our own, and the sodden fields were not more desolate. ”

“ To ascend by holes dug deep in the soft earth was a perilous enterprise. A great clod of soil might at any moment give way above or beneath him, and then he would be plunged once more into the pit. If he fell from the side of the shaft, he would be more likely than at first to strike one of the projecting ledges, and be killed before he reached the water. ”

“ Benching the ground so as to prevent a movement of the toe, does not aid equal settlement nor keep the portion of an embankment above the level of the ground from spreading, except from the resistance offered by the cohesion and friction of the soil; whereas, if the ground slopes inwards towards the centre the earth has a tendency to rest and come together, and therefore not to slip upon the slopes. ”

“ When clay is contained within the walls of a building, injurious action and unequal settlement may arise, as the earth inside and outside may be in a different condition; consequently in soils that expand and contract there may be external or internal pressure according to the state of dampness or dryness, consequent upon the ground outside being subject to weather influences and the contained earth being comparatively free from such operation.
Shale, whether black or brown, may become decomposed by water and be softened by time, and is either loose or firm. ”

“ A short and very high embankment may stand where one of considerable length would slip, consequent upon variations in the character and condition of the earth, the bearing capacity of the ground, the state of the weather, the flow of the surface water, general homogeneousness, the configuration of the ground, and other deteriorating influences; but draining, careful deposition, and a judicious adoption of the varying slope system, and other precautionary works, will conduce to stability. ”

“ Occasionally a subsidence, due to the contraction of the earth’s body, would take place and the sea would again sweep over the entire surface, depositing another layer of silt on the one already formed, or possibly washing that again into sand and pebbles. This process continued through an indefinite period of time, forming layer upon layer of stratified rock, or excavating great hollows in the surface already formed. ”

“ Origin of springs.—The action of running water on the surface of the land having been considered, we may next turn our attention to what may be termed "the subterranean drainage," or the phenomena of springs. Every one is familiar with the fact, that certain porous soils, such as loose sand and gravel, absorb water with rapidity, and that the ground composed of them soon dries up after heavy showers. If a well be sunk in such soils, we often penetrate to considerable depths before we meet with water ”

“ Where the surface soil and underlying drift possess sufficient porous qualities for absorption of a large portion of the rain-fall, together with the natural benefits of the impervious stratum beneath, having a proper axis of inclination favorable for conducting the infiltration of adjoining water-sheds, a large supply of water may be secured by the construction of dug wells for intercepting the subterraneous water. ”

“ In granular soils, such as dry sand or gravel, the earth acts differently and more in accordance with the angle of repose theory of pressure, therefore the strain upon the arch would be the greatest, and its thrust must be counterbalanced at the sides, the strain upon the invert being probably very little and due to the tendency to an overturning movement of either of the straight walls. ”

“ When the parallels and approaches have to be constructed upon ground sloping downward towards the work, in soil containing large stones, or in which the rock is close to the surface, in marshy ground or that containing much water or liable to be flooded, the difficulty of their construction and defilade are evident. ”

“ If the soil which the pile is penetrating be more resisting than that which we have supposed,—for example, if the pile require a direct pressure of 100 tons to force it in,—the same monkey with the same fall would still be sufficient, but the pile would not be driven so far with each blow. ”

“ When a body of clay is encountered and there is reason to suspect that a body of water is being approached, a long drill is used with which to feel the way in advance of the drift, and let the water out, if any there be, in a controllable stream. ”

“ There are numerous kinds of wells, distinguished from one another by their mode of construction, by their depth from the surface, by the fact of their piercing an impervious stratum or merely tapping the first underground sheet of water, and by the height to which the water in them rises or flows. Thus we have shallow and deep wells, horizontal wells or infiltration galleries, open or dug wells, tube wells, non-flowing and flowing wells, bored, drilled, and driven wells, tile-lined and brick-lined wells, and combination dug-and-tubular wells. ”

“ In sandy and gravelly ground, as the particles may be considered insoluble in water and as possessing no cohesion, grass, if it will grow, having deep roots is to be preferred, even if passing through any earth that has been placed upon a slope, in order to counteract the want of cohesion by a greater hold in the soil and any peeling of the turf or tufts forming or becoming detached, rolling down and leaving an unbared surface. ”

“ This is the required inclination to prevent movement provided no pressure is exerted upon the surface, and not taking into consideration the disturbing and weakening effects of vibration and all other deteriorating influences, such as the variable degree of moisture of the soil, the irregularity of its character, the destruction of the continuity of the surface by trenches or drains in a slope, the effect of gravity to detach a mass, the process of excavation or deposition, and the expansion and contraction of soils of an argillaceous nature. ”

“ All his sections were built on the ground on the side of the hill. The problem was to place them in situ without the aid of ruinously expensive scaffolding, and, at the same time, without undue risk to his workmen. Every log had to be laboriously dragged up steep hill-sides, along the bed of a mountain stream, and over ground which would have daunted the resolution of most men. ”

“ It is the nature of this rampart-growing grain to kill out everything else and leave the soil light and mellow. If the ground is encumbered with many stones and rocks, the question of clearing it is more complicated. They can be used, and often sold to advantage, for building purposes. In some instances I have seen laboring-men clear the most unpromising plots of ground by burying all rocks and stones deeply beneath the surface—men, too, who had no other time for the task except the brief hours before and after their daily toil. ”

“ From this brief sketch of the geological structure of this district, considered conjointly with its physiognomical character, the great dryness of the soil may be readily inferred. All the rain that falls on it, or the springs resulting from the partial accumulation and infiltration of this, are either absorbed by the friable soil, by the slaty strata, or are conveyed speedily down the declivities of the solid granite; while the short and declivous vallies, and the almost total absence of plain, afford little or no shelter for them after their descent. ”

“ But in the case of a cutting in drift or permeable soil upon rock or an impermeable surface liable to become wet, which not infrequently occurs, the conditions of equilibrium may easily be destroyed, and the slope upon the higher side may not stand at a less inclination than that of the hill. ”

“ An accumulation of water upon the formation must be prevented, and, as in the majority of cases a railway or road is not level, any collection of water at the commencement of an incline or at a change of gradient should be provided against, and especially any localisation of flow down the slopes from the formation; the main point being to keep a cutting or embankment in a uniform state so that settlement is equable. ”

“ The formation of terraces of earth, and by allowing the ground to subside until movement is arrested, but there may be a porous seam of harder soil, such as gravel, under the soft ground, then care must be taken not to dam back the flow of the underground waters by the subsidence of the added earth or the whole embankment may slide, become softened and finally be swept away ”

“ The material through which the trenches are driven may vary from a sand which can be shovelled without loosening, to solid rock which must be blasted, an intermediate condition of soil being known as hardpan and its excavation costing nearly as much time and effort as rock itself. ”

“ The transmission of water through a porous medium being so rapid, we may easily understand why springs are thrown out on the side of a hill, where the upper set of strata consist of chalk, sand, and other permeable substances, whilst those lying beneath are composed of clay or other retentive soils. ”

“ If however the power of transportation is so great as to remove completely the products of weathering, the work of disintegration is thereby checked; for the soil which weathering tends to accumulate is a reservoir to catch rain as it reaches the earth and store it up for the work of solution and frost, instead of letting it run off at once unused. ”

“ Fig. 96.—Diagram of a valley the top of which is ten times the width of the stream.
Weathering is a part of erosion, but only a part. In so far as it is effected by solution the process involves the transportation of that which is dissolved to some other point. Transportation is also involved to some extent in the other processes of weathering, but the central idea of the processes embraced under this term is the loosening and disrupting of rock by which it is prepared for transportation. ”

“ Weathering prepares the material for transportation and transportation leads to corrasion. Since the goal of all material transported by [Pg 37] running water is the sea, subaerial erosion means degradation of the surface.
Erosion without valleys.—In the work of degradation the valley becomes the site of greatest activity, and in the following pages especial attention is given to the development of valleys and to the phases of topography to which their development leads. ”

“ Buckland, an opinion which was concurred in by Greenough, Conybeare, and other able writers of their time, that the general dispersion of gravel, sand, and loam, over hills and elevated plains, as well as valleys, was the result of a universal deluge, which is described as transient, simultaneous, and of a date not very remote; that the existing system of valleys was mainly due to the same cause, and that thus both valleys and gravels preceded our present river systems. ”

“ When it is known that soft, peaty, muddy, or silty earth overlies level solid ground, and it is certain it cannot escape, and can only be condensed by weighting until it will permanently bear the strain required, it can be built upon; although should there be more pressure at one place than another, or the character of the soil vary, in certain places be swampy and in others dry, the surrounding ground will probably rise where the weight is the least ”

“ In the case of treacherous soil which circumstances compelled to be partly used in a reclamation embankment of moderate height, but which it was found would gradually become firm by compression, rough sheet piles with a plank at top have been inserted, giving the outline of the finished slope of the material to be afterwards tipped upon it, the piles and planking not being removed, and, therefore, affording the required temporary support before the earth became consolidated and stable by compression and time. ”

“ When the configuration of the country allows, it is advisable to avoid cuttings, and particularly embankments, in or upon drift soil lying upon an inclined surface of rock or impermeable soil, because it can so easily be disturbed, become unstable, and of the difficulty of restoring it to a state of equilibrium ”

“ In embankments one of the chief precautions is to obviate any flow of water upon or at a few feet beneath the land upon which an embankment has to be deposited, as it will disturb the feet of the slopes and the base, reduce the adhesion to and the friction of the tipped earth upon the ground and form a sliding surface. ”

“ Recent experiments, however, have shown that in the case of rivers flowing through thickly peopled regions, and especially where the refuse from industrial establishments is discharged into them, the finely comminuted material received from sewers and factories sometimes clogs up the interstices between the particles of sand and gravel which compose the bed and banks, and the water is consequently confined to the channel and no longer diffuses itself laterally through the adjacent soil. ”