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humid, is quite fresh, perceptible currents of air are at all times existing 

 in the more contracted passages, and during our last visit, when a 

 strong breeze was blowing outside, the draughts in these places were so strong 

 that candles could not be used without shelter. This was especially observable 

 in the contracted parts of the north-western cave and branch, in which the 

 current was flowing inwards, in both cases, but in directions diametrically 

 op>posite ; while in the branch of the southern pair, the current was outwards, 

 but only near its outer extremity, being evidently fed by the other branch, 

 which slightly overlaps it about forty feet from its entrance. No visible 

 communication however was observed. The positions and directions of those 

 strong air-currents are marked on the plan by arrows. 



Regarding the origin of these caves, it seems quite evident that the molten 

 lava has found some outlet after the surface has solidified. Some very 

 interesting traces of this, process are visible, especially in the two branches. 

 The floors are covered with curved corrugations, expressive of solidifying while 

 in a state of slow motion, and in some cases the walls seem to have settled 

 down a little, and squeezed the semi-plastic floor into long ridges and 

 furrows. It seems probable that the whole group was formed from one 

 molten stream, and not at different times from different levels. The upper 

 caves, most likely, were formed first, and, after the floor had become Arm, the 

 still-fluid lava below seems to have found some passage downwards, somewhere 

 near the abrupt descent or precipice in the main cave, thus forming the branch. 

 On the face of this precipice, evidence can be traced of the descent of a portion 

 of lava while in an almost solid state. Indeed, at this particular place, 

 everything points to the probability of the lava having found its way into the 

 hollows of some older lava stream. The occurrence of regular chambers, and 

 minor branches, may be explained in the same manner, as the hotter and more 

 fluid lava, collecting in pools, would be tapped and drained away. The roof, 

 where in its original state, is also very suggestive of the above theory. It has 

 all the appearance of some plastic material pulled asunder, having solidified in 

 irregular guttse. 



The percolation of water has, in some places, precipitated, on the surface 

 of the roof, a mineral, generally white, but having, in several places, a red or 

 green tinge. I am not aware of the nature of this mineral, but it is probable 

 that lime, which enters in small quantities into the composition of our scoria, 

 is the chief ingredient. 



Such is a brief and imperfect description of an interesting pjrt of the 

 Auckland scoria beds. The survey was attended with many difficulties, owing 

 to the general roughness, and contracted dimensions of some of the passages, 

 and the use of the level and staff in these, was anything but easy. On these 

 grounds it is hoped that all imperfections will be excused. 



AitT. XXXIX. — -On the Wanganui Beds (Upper Tertiary). By J. Buchanan, 



of the Geological Survey of New Zealand. 



[Read before the Wellington Philosophical Society, September 18, 1869.] 



The following notes give the results of a comparison of the fossil shells from 

 the Upper Tertiary stata of New Zealand, which are in the Colonial Museum, 

 with the fossils obtained by the author, in that portion of the formation 

 locally known as the " Wanganui series " : — 



"Wanganui Beds (Upper Tertiary). 



The information, respecting the latter series, is founded on personal 

 examination of the cliffs of the Wanganui river, near the township, and 



z 



