288 Proceedings of the Royal Physical Society. 



position of the point of stream-junction is ob\dously a 

 vacillating one. These triangular haughs, in fact, may be 

 likened to flat-pointed boards, from the two edges of which 

 a boy is occupied in taking out large scoops with his 

 knife, now on one side, and now on the other. It will be 

 found that one or other of the two streams is in process 

 of sweeping-in with a curve, which must, as it advances, 

 cut away a section of the triangular flat, giving the stream 

 a fresh opportunity to form a new haugh, at a lower level, 

 and in front of the first. By these means, as the valley 

 deepens, a whole succession of terraces, more or less prow- 

 like in profile, may stand above one another (Fig. 13). The 

 more shifting of the two streams tends to drive the point of 

 the prow further towards the other. Like amphitheatre 

 terraces, these junction terraces are formed independently 

 within their recess, and have different heights compared 

 with the terraces at other parts of the stream. 



Lateral Terraces : 3. Indeterminate Varieties. The Lateral 

 Terrace proper. 



It would be well that the terms amphitheatre terrace and 

 junction terrace were restricted to terraces having so definite 

 a relation to the play of shifting bends within persistent 

 ones, or at stream-junctions, that they may be identified 

 as having been, so to speak, born and cradled where they 

 now lie. Considerable numbers of terraces, originally belong- 

 ing to the amphitheatre variety, may of course have been 

 formed within bends which, though at the time relatively 

 persistent, are now lost. The changes that have been 

 wrought in many valleys, since planation first produced 

 terraces in them, have often necessarily disconnected ter- 

 races from their original environment. There is also an ill- 

 defined group, exemplified by the lower terraces in Fig. 16, 

 of which all that can be said in the way of definition or 

 nomenclature is, that they are lateral terraces, having no 

 very determinable relation to persistent bends, formed in- 

 dependently on the opposite sides of streams, and not usually 

 exactly vis-a-vis. The typical member of this group is a 

 terrace due to lengthened traverses of the river-bank by 



