Cotton. — Notes on Wellington Physiography. 259 



be regarded as having extended at least a mile out into the waters of 

 Port Nicholson, enclosing between them the continuations of the present 

 eorees: and the coast must have been cut back to a straight line by 

 wave-action. 



The problem may be attacked in two ways : (1.) Search for the 

 rock platforms which should remain to indicate the former exten- 

 sion of the spurs. A glance at fig. 5 shows that these are absent, 

 and that the deepest water of Port Nicholson comes close to this shore. 

 Rock platforms, if they existed, ought to have been actually raised 

 above water by the 5 ft. uplift of 1855, but for nearly the whole length 

 of the scarp rocks are not exposed at low water more than 50 yards 

 from the foot of the cliffs. (2.) Comparison with other parts of the 

 coast-line where marine erosion has been more or less effective in cutting 

 back the coast, The coast of the seaward end of Miramar Peninsula 

 (fig. 6) may be considered. Here, indeed, bluffs have been cut back to 

 the extent of a mile, as the exposed rock platform at their base shows,, 

 but the coast has by no means been rendered perfectly straight. More- 

 over, compared with its activity on the outer coast, wave-action within 

 the harbour is extremely feeble. A safe comparison can therefore be 

 made only with another stretch of coast within the harbour. When the 

 eastern shore is examined it is found that wave-action has succeeded 

 only in shaving off the ends of points. Fig. 11 represents the eastern 

 shore as seen from the signal-station on Miramar Peninsula. Its 

 irregular base-line may be noted on the maps, figs. 1 and 5. It 

 should be noted that this side of the harbour is bounded by a strike 

 ridge, and that no spurs of any magnitude run down from it. So a shore- 

 line originally nearly straight has been rendered but little straighter 

 by wave-cutting. Moreover, the increasing height of cliffs towards the 

 harbour - entrance shows that the greater part of the work has been 

 done by waves rolling in from the open sea. The western shore of the 

 harbour, on the other hand, is affected only by waves raised on the 

 harbour itself. The effect of waves raised within the harbour is seen 

 on the shore of Evans Bay (on the left in fig. 6). 



The conclusion reached is that the scarp bordering the harbour on 

 the north-west, with its straight base-line, cutting at an angle across 

 the strike both of the rock strata and of the drowned ridges to the 

 south of it, with its faceted spurs and its steep-grade gorges, is the 

 result of recent faulting. Fig. 9 may be compared with the sketches 

 and photographs of the Wasatch Range given by Davis,* and also with 

 the diagrams illustrating his theoretical discussion of the dissection of 

 the face of a faulted block. f 



Nature of the Movement. 



The fact that the portions remaining of the scarp along the fault- 

 line are inclined back at an angle of about 55° may indicate that the 

 surface along which movement took place had that inclination. On the 

 other hand, if the fault-plane were steeper the slope would quickly be 

 reduced by slipping along the crest of the high block. 



* W. M. Davis, Bull. Mus. Comp. Zool., Harv., vol. 42, No. 3, 1904, p. 153, ar.d 

 pi. 4 ; and vol. 49, No. 2, 1905, fig. 2, and pi. 1, a. 

 t Loc. tit., vol. 42, No. 3, 1S04, fige. 6-9. 

 9* 



