The great point is to confine a “boil” within a certain space, and there to treat it and so prevent the appearance of others and interruption to the prosecution of the works. All agitation of the surface of sand, especially when a “boil” appears, must be prevented, as inducing a disturbed and more porous condition. When the seat of a “boil” must be built over, the well system of foundations can be used as not only affording reliable support, but also preventing a “boil” extending, and allowing the flow of water to be discharged, care being taken that complete connection is made with a wall constructed upon any other principle. If “boils” appear over a considerable area, it is evident that the disturbance is general, and may either be because the site or the foundations of the works are below the level at which water is usually found in the district, or be produced by the rise and fall of tidal waters. When by the former, drains are required a few feet below the general water-bearing level, and they should intercept the percolation of the land waters and conduct them from the site of the works, or so gently localize them that they can be treated as before described. The land waters are the most troublesome because their volume, time of appearance, and duration of flow will vary, whereas the range of the tidal waters is known, and therefore the effects may be ascertained with some approach to accuracy. It may be impossible to erect walls in very loose soils without encircling the site with sheet piles to prevent a run of sand, to lessen “blows” and to reduce the disturbance, as placing them upon an impervious stratum maybe prohibitory because of the expense: but the adoption of the well system of foundations down to a firm stratum, or at a sufficient depth to be stable, and the building walls thereon may cause the temporary pile support to be unnecessary and prevent a slip or subsidence. Quick erection and the least exposure or disturbance of earth are essentials in such cases. By the use of Portland cement concrete, foundations can now be cheaply obtained with the ground in a wet condition, which in the days when it was considered only suitable for secondary works, would have required the employment of expensive methods of construction. It may be unwise to arrest the upward flow of the tidal waters in loose soil except by intercepting, lessening, or preventing it by shore protection, for the upward pressure of the head of water may “blow” up the earth and cause disturbance; on the other hand, should the “boils” be merely superficial and the head very little, a thick watertight covering of Portland cement concrete, when accompanied by the necessary drainage operations, may suffice; the surface water blows being covered, and the pressure of the water being overbalanced by the superimposed weight.