Where a dry dock had to be made upon soft fine sand, Portland cement concrete has been successfully used to cover the whole site. In such soils, to avoid the danger of the bottom being blown up when a dock is empty, and has not the counterbalancing weight of a ship, arrangements should be made so that sufficient water is let in to counteract the uplifting force. If it can be avoided it is advisable not to erect a graving dock upon very porous earth, as the expense of an impervious lining, whether of Portland cement concrete or clay puddle, and of keeping it dry will be considerable; and when unequal settlement takes place a run of the soil may occur and a slip of earth cause it to become fissured and separated, especially in an estuary or bay with headlands, as natural springs may make the sand a quicksand. Much depends upon the head, if the water comes from the adjoining hills it may be so great as to prevent any but a strongly constructed dock, acting as a watertight box, being successful. The bearing power of the soil will also be practically the same whether the foundations are a few feet or at a considerable depth, as the head will be sufficient to make the springs issue, and therefore disturb the earth. The drainage of the site requires to be carefully deliberated, and no rules can be laid down, but the flow of all surface water and springs should be controlled. The chief aim should be rather to prevent water reaching the site than to allow it to be present and then pump it away, hence it is well to have the deepest sump and all water-raising apparatus, if possible, outside the area of the works of art and in the direction of the land or river flow. The first operation in draining the site is to construct the necessary surface drains around it and also the sinking of a sump, cylinder, or wells where required, which to be effectual must be some few feet deeper than the lowest level of the works of construction; but the depth should be no more than is absolutely requisite, as the greater the lift of a pump the less the efficiency; care being taken that the bottom of the sump is sufficiently low that water gravitates to it, and that the pumping apparatus is at such a height that it cannot be “drowned.” When the soil is of so loose a character that pumping will cause it to “run,” the bottom can be closed and holes made in the ring and water pumped in through them, and in addition coarse gravel or broken stone can be inserted to act as a filter. The act of drainage may cause soil that has been full of springs to be entirely free from them, and cannot but always tend to consolidation, if only because of settlement and the interstices or fissures being less occupied by water or being reduced in size. In loose soils, especially at the commencement of pumping operations, it is advisable that it be not very rapid, as a quick change of condition may cause the ground to be disturbed too much, whereas slow pumping may