With few exceptions the exterior or faces of cuttings and embankments will, at certain times, become impaired or soddened by the infiltration of water. In cuttings there is the additional danger, owing to the geological formation, of the excavation reaching the depth at which water is generally found in the locality, and it is therefore advisable to ascertain this level, and also to decide whether the ground must be excavated below it, as necessarily there will be a downward flow, and the slopes and formation will consequently have to sustain a pressure due to the difference between the normal level of the water-bearing stratum in the neighbourhood and that of any depth beneath it. In such a case, in addition to the usual softening and loosening aqueous action, there is the particular insecurity of the formation and slopes being undermined and eroded by springs: also in pervious soil in a drained district a cutting will be found to be comparatively dry to about the level of the bottom of the existing contiguous drains, but below that depth water will be present, probably in considerable quantity. Land drains also frequently cause slips, as they localise the flow of the surface or underground waters, and when in excavating a cutting they are intercepted, the discharge should be led away from the slopes; but difficulty may be encountered in effecting this, as water will usually follow its original course, and it may be impossible to entirely divert the direction of the flow, and the only thing to do may be to gently conduct the water down the slope by means of pipes, rubble, burnt brick, gravel surface drains, or timber ducts. An important question to determine is, when are slips in earthwork most likely to occur. In Europe they are most frequent in the autumn and winter months; but no rule can be established, nor is it reasonable to conclude, because any earthwork has remained stable during the usual period when slips may be expected, that, therefore, none will happen, for the heaviest rain may descend at an unusual season, and as moisture is the chief cause of the instability of all earths, it is rather to the quantity of the rainfall at any time than to the fixed seasons that attention should be directed.