296 



Transactions 



able at present, however, merely to hint at a few points. The physio- 

 graphy of the Hntt Valley is a subject that deserves careful investigation 

 and thorough treatment. 



The lower portion of the valley is undoubtedly a part of the Port Nichol- 

 son depression, resulting from the inbreak along the Wellington fault, that 

 has been filled by a delta built forward by the Hutt River. This is proved 

 by the continuation of the fault-scaip into the lower valley without break. 



There appear to be good reasons for believing that the valley of the 

 Hutt River to its very source is determined by a line of faulting which 

 continues the line of the Wellington fault ; but it has yet to be shown 

 how far the valley is n fault valley, and how far a fault-line valley. 



The predominant, longitudinal, topographic features, which I regard as 

 guided by the strike of the strata, trend rather more north easterly just 

 north of Wellington than they do in the south of the peninsula ; but within 

 the basin of the Hutt they are again nearly meridional, trending about 

 N. 10° E. Everywhere the valley of the Hutt meets these longitudinal 

 features at an acute angle (see fig. 1). The Hutt River, which flows 



Fig. 1. — Map of the Hutt River System, 



S. 60° W., receives tributaries flowing on the one side S. 10° W. and on 

 the other N. 10° E. In the field this is most conspicuous, though the 

 map shows it well only in the case of large tributaries like the Mungaroa 

 and Akatarawa. 



Eight miles from the mouth the broad plain of the lower Hutt Valley, 

 which is probably all delta, ends, and the valley, narrowing almost to a 

 gorge, is clearly the work of erosion. Farther up, the valley opens out 

 again, and for five miles has a flat floor, in places a mile in width. The 

 valley here is strongly asymmetrical. The south-east side is formed by 

 long, sprawling, gently tapering spurs, the lower ends of which seem to be 

 buried in an aggraded plain. The spur-ends are not truncated, and thus 

 there is no evidence that the valley has been widened by the river swinging 

 against this side. The north-west side is, on the other hand, formed by 



