GEOLOGY hills permit of its observation better, the dip-slope is from two to three times longer, and proportionately less steep than the slope facing north- west, or scarp-slope as it is called ; also the long slope is often hummocky from the presence of still undenuded slipped matter, which acts as a buttress to prevent further slipping for a time. The steep slopes of hills facing points of the compass opposite, or ap- proximately so, to that of the direction of dip of the beds, and therefore exposing the edges of the constituent rocks, are called escarpments. Natu- rally high-level slips do not readily occur on these steep slopes, because the beds dip and the water flows the opposite way ; low-level slips however are more likely to occur, because of the higher gradient, but since the material of such slips is carried to a lower level at first, and there left in a more shattered condition for denuding agents to act upon, these scarp- slopes are generally more regular in appearance. A very irregular scarp- slope may be taken as an indication of comparatively recent slipping. Perhaps the roughest steep slope to be found in Northamptonshire occurs between Rockingham and Gretton, facing the Welland valley, and its present instability is shown by periodical damage to buildings on it at Gretton.' Anticlines, Synclines, Faults Quite independently of the general dip of strata on a large scale, and of the contour of the ground, it is common to find local folding on a small scale. The upward curve of a fold is called an anticline and the downward one a syncline. In some places the fluctuations are so gentle as to suggest that they are the result of deep-seated stresses ; such have been detected at Finedon and elsewhere. It is at first sight most singular frequently to observe, when a good hill is cut into, that the strata dip into it, and rise towards the adjacent valley, that is to say hills cover synclines and valleys occur over anticlines. If we can believe that the enormous pressure of a great thickness of ice caused depression of the whole land in glacial times, and that the land rose again when the pressure was taken off, then can we understand how wet plastic clay will bulge upwards as the load above it is removed in the cutting out of a valley, and that the adjacent hills which supply the pressure will sink to a proportionate amount. It is exceedingly common to find, on digging into the ground, that a slip has occurred, so that the ends of originally continuous beds are met with at different levels. These %o-czc6. faults are far too numerous and complicated, and often too insignificant, to have had a specific deep- seated origin. All that have been detected are newer than the latest regular local rock, but older than the Glacial period. On the i-inch maps of the Geological Survey all important faults known at the time of the survey are marked in white lines, but of course others have been discovered since. ' John W. Judd, * The Geology of Rutland, etc.* Memoirs of the Geological Survey, p. 261. 33
