SURFACE SLIPS 43 



the water at her bow. The weight of the mass had been so great that 

 notwithstanding its drop or rather precipitous slide of ten or fifteen 

 feet, the grasses and flax on its top had perfectly retained their natural 

 angle of growth. Although, however, only three limestone quadri- 

 laterals have thus been detected in motion, I believe that the numberless 

 boulders already broken from the cap and deeply embedded in the 

 hillsides really never cease to move, that they are being slowly sucked 

 downhill, perhaps an inch or so a year, sapped by the action of 

 innumerable under-runners. 



Alterations in the positions of the large-sized river-bed boulders 

 have hardly been more conspicuous. Certain very noticeable fragments 

 have moved a foot or two ocean wards. The ford of a river is more 

 closely scanned than any other portion of its bed : that of the Waikoau 

 has scarcely changed in forty years. We cross now or did until the 

 bridge was built within a few yards of where we crossed in '82. 



Two minor processes of erosion yet remain unchronicled, the more 

 important I believe responsible for the circular pits found over the relics 

 of the ancient plateau caps of eastern Tutira. Sometimes these funnel- 

 shaped cavities are still skinned over by turf, sometimes the turf has 

 broken through and they are open at bottom. Most of them are of 

 moderate depth. One pit, however, within a short distance of the 

 Tutira boundary, was, until opened up by spade-work, a death-trap for 

 animals. At its base remains of sheep and pigs used often to be visible, 

 the former presumably tempted over the edge by succulent weeds or 

 trapped by mere bad luck, the latter induced to slide down by the 

 bait of the former and then unable to escape. These pits, great 

 and small, have been probably worn by the action of the carbonic 

 acid of rain-water affecting the limestone rock-cap. Its substance 

 is dissolved and borne away as travertine, masses of which accum- 

 ulate about the sides of the streams. Consequent on the chemical 

 dissolution of the rock-cap beneath, the unsupported soils slide down- 

 wards towards the centre of weakness, thus forming rudely circular pits. 

 Withdrawal of matter from beneath may also be held responsible for 

 the almost perfectly moulded funnels alongside of one of the streams 

 of this part of the station. It runs over a jumble of squares, cubes, and 

 slabs sections that have broken away from the limestone cap and been 

 carried violently by earth avalanches or mined by under-runners into 



