GEOLOGICAL MAPS 163 



nearly at right angles to the under-surface of the hard bed ; and 

 the more resistant that bed, the nearer will the actual slope con- 

 form to the theoretical. This is the scarp or escarpment, and, 

 though usually grass-covered, it sometimes presents a cliff of bare 

 hard rock (Fig. 53). The soft rock which occurs beneath it is 

 generally denuded back until protected by the overhang of the 

 hard rock, and so its slope may also be steep, and it will sweep 

 upwards to the hard rock cornice in a beautiful parabolic curve. 

 This is the typical scarp outline. 



Valleys may generally be found cutting across wolds in the 

 direction of the dip of the rock, and the streams usually flow in the 

 same direction as the dip arrow points, e.g. from strata lower to those 

 higher in the sequence. These transverse valleys, or, as they may 

 now be termed, dip-valleys, will be much steeper-sided when travers- 

 ing hard rock, and more open and V-like in crossing softer rocks. 

 The tributaries of these streams will be the longitudinal streams 

 flowing down the strike-valleys until they join their own trans- 

 verse stream (Fig. 48). Thus the transverse valleys are often the 

 most striking features in the landscape of a wold country, and 

 their behaviour at first seems anomalous, because they appear to 

 cut deep, steep-sided, valleys through hard rocks when there often 

 seems to be an easier path round the obstruction. A still more 

 curious feature is the fact that in many cases the land at the head 

 waters of this type of stream is less conspicuous than the ridge 

 or ridges they traverse (Fig. 64). 



Still a third type of valley comes down the face of the escarp- 

 ments, flowing in the opposite direction to the dip of the beds. 

 These are obviously related to the scarp slope itself, and must 

 have arisen after the scarp was formed, and, starting down its 

 steep slope, must have cut their way back into it. Their valleys are 

 comparatively steep, and the streams short and rapid ; in extreme 

 cases they form rapids and waterfalls (Figs. 40 and 69). It is to them 

 that the slight curves and recesses in the straight line of the scarp 

 are due (Fig. 44), and their denuding work is carried on chiefly at 

 their head waters, which are constantly eating back and thus 

 lengthening the streams. They might be called counter-dip streams. 



It will be seen that if the hard and soft rocks are responsible 

 for defining the features of a country, and if the whole country 



