Purnell. — On the Wanganui Tertiaries. 455 



Tongariro. The lowest stratum visible here is the red clay — a volcanic 

 product. Then comes the pumice bed itself, extending miles and miles in 

 length and breadth, a terrible witness of the vigour of a huge submarine 

 volcano, whose effects were augmented here and there by lesser outlets, as in 

 the cliff mentioned. A long interval of calm must have supervened to allow 

 of the deposition of the blue clay, and the birth and death of the inhabitants 

 of the many generations of shells which there lie buried. Another mud torrent 

 from a distant point followed, rolling over the blue clay, entombing its 

 molluscs, and covering it at Shakespeare Cliff with a layer ten or fifteen feet 

 thick, and elsewhere of a much greater thickness. Again, volcanic activity 

 ceased for a time, and for no brief period, since it was long enough to allow of 

 the accumulation of a shelly stratum twelve to eighteen inches thick, with a 

 large Pectunculus as its characteristic fossil. But it was only the prelude to 

 a more terrible fiery storm. A perfect deluge of mud came down, forming a 

 layer fifty feet thick, and covering perhaps as spacious an area as the 

 pumice. Upon this lies three feet of marine clay, with recent shells. 



Superimposed is a remarkable bed of dark cemented gravel, ten to fifteen 

 feet thick, covered by twenty feet of loose grit, both without fossils. This bed 

 of cemented gravel is exposed at Shakespeare Cliff, at the cliffs below Putiki 

 called the Landguard Bluff, at the end of Victoria Avenue, and in several 

 other places situated at a distance from each other, showing that it likewise 

 spreads over a large tract. Was it the bed of a lake occupying the present 

 valley of the "Wanganui ? It bears the aspect of a lacustrine deposit, and the 

 overlying beds in the sections made by the roadmen in the cliffs at the west 



be 



character. 



The gravel is capped by one hundred feet and more of volcanic mud, which 

 in many places has suffered much from denudation. An indication is given of 

 how denudation has lessened the thickness of this bed, and perhaps of the 

 lower mud beds also, at the Landguard Bluff. There is a fault here, the bluff 



bed 



cliff 



the depth of the fault has been denuded. 



The foregoing remarks will give an idea of the force and long duration of 

 volcanic eruptions in this region ; but only an idea, because there is no section 

 of country laid bare which reveals a full development of the series of eruptions 



and intermissions. 



be expected. "We 



above 



Cliff is only from twelve to eighteen inches thick, expands at the Landguard 

 Bluff to a stratum twenty feet thick, composed almost entirely of shells, 

 a large Pecten (P. jacobceus) here playing the part which Ostrea does at 



