196 



TUTIRA 



Throughout the pumiceous area, where the soil is gritty and friable 

 and where erosion is easy, there can be noted in these shelves a certain 

 troglodytic tendency, their backs slightly concave, or, at any rate, per- 

 fectly upright and bare of grass. On stiff 

 lands, in fact, the shelves tend to work 

 outwards, on friable soils to work inwards. 



Another minor physical change, also 

 attributable to stock, is the earth-bubble. 

 These surface swellings are the result of a 

 blocked soakage system ; they commonly 

 appear on the higher side of tracks, where 

 the upper crust has been hardened by 

 traffic, where free escape of water during 

 heavy storms has been impeded. The sub- 

 terranean creeks, or under-runners, on the 

 upper side become gorged with water that 

 Earth-bubble cannot immediately drain away; reaching 



ground beneath which it cannot pass 



ground toughened and kneaded into some sort of consistency by 

 the tread of stock and comminglement of mud and manure, it 

 raises soft tumours which, when lanced by a sharp stick, eject con- 



L.-J? tr^X-'ffZr^^-Zr^^r^*^. 



During flood. 



siderable jets of muddy water. These minute phenomena are 

 evanescent and soon subside. Though of considerable depth, the 

 biggest do not exceed a couple of feet in diameter and a few 

 inches in height ; of the many surprises awaiting shepherds after 



