All works to prevent “boils” or to drain waters from the site should, if possible, be executed prior to the excavation, as the effect of draining can then be observed and whether any “boils” arise from land waters or from a tidal flow, and the earth will have had some time in which to subside and become consolidated. A month’s test will afford some criterion in a variable climate and when changes of weather are frequent; but should a long period of drought prevail it may be no indication of the state in which the earth would be in a wet season, or under ordinary meteorological influences; and further, the land waters may take a considerable time in flowing to the shore, depending upon the catchment area, character of the soil, position of the beds, whether the district is drained or not, and many other local conditions. When the soil is firm clay, the locality of any leakage or water seam in it will usually be indicated by surface exudation over the water-charged vein; also in nearly all compact earth, particularly if of a clayey or loamy nature, and therefore the seat of disturbance may not have to be discovered as in looser or sandy soils. Should a water-bearing fissure occur in rock and it be necessary to stop it, there being no danger of diverting the flow to another place upon the site of the works, it can be done by means of neat Portland cement mortar pressed down and kept in place by timber strips, weights or other means until it has set; the face of the fissure should be made as clean as possible, and the water-bearing seam be filled and weighted directly a leak appears, or the flow may become much increased and accelerated and a current of water be induced which may become of serious extent. To avoid slips and movement of the ground when it is necessary that a water-charged bed of sand be excavated to enable a structure to be built upon a firm impervious stratum below it, sheet piles can be used or corrugated iron sheets, strutted at intervals, so as to prevent a run and slip of sand; and the space between them can be excavated, a Portland cement concrete foundation being inserted upon the firm soil, the wall being erected in lengths, and the piles or case being practically three-sided so as to leave no unsupported surface of sand, care being taken to prevent any run between the front and the back of the last built length of wall and the earth, so that each length is erected in a contained area. INDEX. A. Absorption, broken earth, 70 ——, chalk, 29 ——, sand, 34 Alignment of public works, _vide_ location, 9–12, 146 Alluvial deposits, safe load upon, 88–89 ——, soil, slope, 100 ——, protection of the banks of rivers, 126 Angular particles in earth, 36 Approaches to culverts, 84, 85 Arched system, dock-walls, 210, 211 Argillaceous rocks, slopes, 24 Ashes, slope, 100 Atmospheric pressure, influence of, 17