24 TUTIRA 



stone fine ground, its greasiness resulting perhaps from some admixture 

 with the scanty pale clays found on the eastern run. Perhaps, too, the 

 coloration of the deposit may be derived from sources similar to those 

 which give the conglomerate beds their rusty ferruginous hue. 



Proceeding still from below towards the top, we come upon the 

 band of pumice grit that lies on the red sand. It is about four inches 

 in depth, the grit perfectly loose and dry, its grain very even, in size 

 resembling the granules of a rough brown sugar. It is remarkably un- 

 clogged and free from intermixture of foreign matter. Like other bad 

 things, it has reached Tutira from one or other of the inland volcanoes 

 of the North Island. It is, I think, seolian, wind-carried, and has probably 

 descended on a countryside supporting a vegetation thick enough, stiff 

 enough, and high enough to afford immediate shelter and cover. Its 

 light dry substance, falling like rain from above, would thus either 

 percolate direct through this growth or be at once watered on to the 

 ground by wet weather. It would lie evenly on the ground as in fact 

 we find it in the undisturbed plateau fragments and during succeeding 

 centuries become covered with root matter and leaf-mould. The vege- 

 tation which thus sheltered and harboured this pumice shower must 

 have been then growing on red sand, for it cannot be doubted that the 

 top spit of humus is merely the accumulated result of decayed vege- 

 tation. The pumice deposit appears to have been the result of a single 

 volcanic outbreak. Nowhere, at any rate, do I find the slightest trace 

 of alternate layers of grit and humus. The two substances are clearly 

 distinct. Other showers of pumice may have fallen at other periods on 

 naked surfaces and been blown off, but the result of the one particular 

 eruption incorporated in the soil of the station fell, I believe, on a 

 surface protected from wind. Unless we are to suppose different 

 meteorological conditions, no layer of grit could have endured one hour's 

 nor'-west gale on bare baked sand. Even by the less violent action of 

 rain it would have quickly been washed away. 



The alternative to the theory of wind-blown pumice is to suppose the 

 grit to have fallen on water and eventually to have sunk. There are 

 many difficulties, however, to be faced. Falling on open sea the light 

 material would have been soon dispersed ; even granted that it may have 

 fallen on landlocked waters, the floating masses would have been heaped 

 together by action of wind and wave, the grit would not have been 



