156 J. MALCOLM MACLAREN, ESQ., B.SC, F.G.S., ON 



Period by snow-fields, while the old g-lacier beds are still 

 submerged. The dense vegetation also prevents other than 

 a cursory search for the signs of past glaciation. 



5. The effects of Glacier Erosion. — The glaciers which 

 occupied these valleys possibly, and indeed probably, 

 augmented their depths. Nevertheless, for the New Zealand 

 sounds, I have never been able to accept the glacier rock- 

 basin theory, mainly because their cross sections do not 

 coincide with ray idea of those of a typical glacier excavated 

 rock basin, which, I think, demands sloping instead of per- 

 pendicular sides ; and also, because the singular isobathic 

 contours may be explained much more simply tlian by calling 

 to our aid such doubtful phenomena, in this case, at least, as 

 glacier excavated rock basins. It is quite possible that some 

 portion of some of the bars at the fjord mouths may be 

 vestiges of terminal moraines, but if so, their presence at that 

 point is probably accidental, and is in nowise essential to the 

 formation of such bars as do occur. An ample explanation 

 is derived from a consideration of the prevailing currents 

 and winds on this coast. Along the western shore of the 

 South Island there sets to the S.S.W, a current which runs at 

 the rate of one to one-and-a-half knots per hour — and a 

 current which is considerably accelerated when the prevailing 

 N.W. wind is blowing. 'The two combined are sufficient to 

 cause a southerly drift of shingle and gravel along the shore. 

 It is from this cause that all the harbours on the west coast 

 of New Zealand are bar harbours, and where breakwaters 

 have been built and artificial harbours made, the result soon 

 shows a struggle between nature and man for the mastery. 



6. Eff'ects of Ocean Ciirrent?. — The drift takes place until 

 the mouth of a fjord is reached and. in the resultant eddy, the 

 gravel and shingle are swept into the still water of the fjord, 

 forming a bar, the inner slope of which is regulated by the 

 slope angle which such materials assume in water under given 

 conditions. As the rise and fall of the tides is here ver}^ 

 small — from 6 to 8 feet only in springs — and the entrances to 

 the sounds are not at all constricted, no strong '" rip " or 

 current is developed to keep the mouth clear. That the 

 above has been the main, if not indeed the sole cause, of the 

 shape of the fjord beds at tJieir mouths may perhaps be more 

 readily admitted when it is stated that an examination of 

 some of the arms of the sounds shows bathymetric features 

 similar to those already described. For example, m South 

 Port — a cove in Chalky Sound — we have nmch greater 



