Coverings can also be made of a thin coating of burnt ballast, hard chalk, or gravel, which will reduce the number of cracks or crevices, or a mattress of fascine work can be used at the toe of the slope in submerged work, but care should be taken that the mattresses overlap and that there are no open places between them, or, instead of being a protection they will then be a source of danger by conducting water between the joints; for this reason, as with any other material having loose openings, it is advisable to use them over a continuous surface so that percolation may be uniform and not simply for weak places or for the purpose of repairing a slip in an earth embankment. The chief aim in fascine work is to thoroughly bind the work together so that it is of equal strength in all directions, and a little time after construction should be allowed before deposition in order that the material may settle, as an even surface is important. The most durable material should be used in making a fascine covering, willow being the best, or it may require constant renewing. Alder, aspen, and the best available brushwood are also employed, and straw and ordinary matting for shallow embankments, say up to 8 feet in height, which lasts only six to twelve months. The best time for cutting should be locally ascertained, and when they commence to deteriorate after being hewn, generally from three months to a year, depending upon the season in which they are cut, &c., &c. In England, thorn switches have been used in lengths of 5 to 6 feet, tied up with tarred rope in bundles having a diameter of about 1 foot, every endeavour being made to bind and interweave them. Care must be taken that the mattresses are well loaded or they will float; the loading should commence at the centre, and be equally continued in all directions, as that has been found to be the best method; they should be made to sink evenly if they have to be lowered through water, and they must be prevented from curling up at the edges. The props which fix them must not be too close to the border, or near the centre, as then the extremities will be torn away or bent upwards. The system of fascine work may be very useful for protecting sandy and soft foundations in such situations, to prevent slips in the slopes of an embankment and in providing a firm bed, and also for making training banks, groynes, and spurs, for correcting and directing a current in a desired channel, and to secure freedom from slips in a river-bank. Depending upon the degree of looseness of the sand or sandy bed, loaded fascine mattresses will assume a slope of from 1 to 1 TO 5 to 1 if allowed to sink in the bed, and after they have settled and reached the angle of repose which the action of water will effect; the large number of structures standing upon them for many years in considerable depths of water proves, when they are properly made, that they are to be trusted in comparatively unexposed situations.