MuLGAN. — The Northern Wairoa. 455 



proportions, seeing that the area over which it is distributed 

 is so small in extent. In point of fact, the rainfall across that 

 portion of the Auckland Peninsula is exceptionally great. 

 The prevailing westerly winds, after their passage over the 

 Tasman Sea, reach the relatively high land heavily laden with 

 moisture, where the inevitable lowering of temperature brings 

 about a constant precipitation of rain. I was unable to ob- 

 tain reliable statistics touching the rainfall, but several well- 

 known facts pointed to its great abundance. When the sur- 

 veyors and parties were cutting the track for the road througli 

 the Awatuna and Marlborough Settlements they found the 

 ground very damp and soft, and the tree-trunks covered with 

 moss and hchen. The ground was frequently buried to a 

 depth of several feet in moss, and was everywhere saturated 

 with moisture. The men employed on the work suffered 

 much from the wet and damp, some of them being obliged 

 to give up their employment in consequence. Then, again, 

 the settlers experience great difficulty in burning off the bush. 

 "It will not burn," they say — a statement to which the 

 half-burnt logs and ill-cleared land bear ample witness. One 

 cannot help noticing the readiness with which the scrub 

 (chiefly makomako — Anstotelia racemosa) comes up in the 

 clearings, and the small extent of land which is really freed 

 from bush, as also the extreme moistness of the land itself. 

 It seems unnatural to find soft boggy soil at such a high 

 elevation— to find it, in fact, on hilltops. 



That there is very considerable rainfall cannot be doubted, 

 and this, added to the size and configuration of the catchment- 

 area, accounts for the dimensions of the river, which at first 

 sight would appear out of all proportion to the conditions 

 under which it exists. 



The fall of the river from the Junction to the sea is very 

 slight— only a few feet — for the effects of the tide are felt 

 considerably beyond that point. This implies that the velo- 

 city of the stream itself is small, hence we would expect to 

 find, as is actually the case, a wide flat-bottomed valley filled 

 with detritus. 



From the Junction to the sea the Wairoa has lost the 

 power of vertical erosion. The banks of the river, however, 

 are soft, and the load of sand and mud carried by the water is 

 very great, conditions highly favourable for lateral erosion, 

 hence one is not surprised to find that the river has cut for 

 Itself a very winding channel. It is well to remember, in 

 considering the work done by rivers, that running water is 

 only the motive power, and that the instrument which really 

 does the work is the sand and mud carried along by the water. 

 A perfectly clear stream running over a bed of sand and 

 pebbles which do not move is doing no work at all; it is only 



