Ceawford. — Geolocjy of ilic North Island of New Zealand. 307 



island) to tlie northward and eastward of a line struck from the soutliern 

 slopes of Mount Egmont and Euapeliu, and are broken tkrougli by volcanic 

 rocks, wbieb, to a considerable extent, overspread their surface. 



The secondary or mesozoic rocks as yet discovered or positively known 

 occupy an area of moderate extent, and the greater part of the surface of 

 the island is covered by the above strata of tertiary age, both sedimentary 

 and volcanic. 



Before entering upon a description of the palaeozoic rocks, it is however 

 necessary to state that there is reason to suspect that a considerable pro- 

 portion of the rocks now classed as palgeozoic may have hereafter to be 

 transferred to the mesozoic list. Dr. Hector thinks that the sandstones and 

 slates associated with the plant beds near Wellington have a strong 

 resemblance to mesozoic rocks elsewhere in New Zealand, and that they will 

 probably be found to lie unconformably upon the older diorite rocks of the 

 neighbourhood ; while I have a decided impression that the rocks of the 

 ranges at Cape Palliser will pi-ove to be of later date than those of the 

 Eimutaka Eange on the eastern side of the Wairaraj)a. "With the above 

 understanding, it will be as well, for present purposes of description, to 

 consider all the apparently old and highly inclined rocks of the great leading 

 ranges of mountains as of palaeozoic age. 



Primaet or Palaeozoic Eocks. 



There is reason to suppose that the palaeozoic rocks, which are almost 

 invariably found highly inclined, decrease in geological age from west to 

 east. They appear to have been subjected during the lapse of ages to 

 extreme lateral pressure, Avhich has thrown them, particularly towards the 

 eastern or main ranges, into abrupt mountain ridges, extending in a N.N.E. 

 and S.S.W. direction, and enclosing only very narrow valleys. Except where 

 these mountain ridges rise from out of the tertiary covering, the indication 

 of their existence can often only be proved at remote spots, where the 

 violent torrents near the sources of the great rivers have scooped out deep 

 gullies in the soft tertiaries, and left a flooring of old slates or sandstones 

 exposed in their beds. 



Although the volcanic chain of Euapehu and Tongariro may be said to 

 be the leading feature of the North Island, rising as it does from a very 

 elevated plateau, one of its cones, Euapehu, being the highest mountain in 

 the island, yet Ave cannot consider this isolated chain as the leading range, 

 but must award a higher structural importance to the palaeozoic ranges 

 further to the eastward. These ranges, though broken, pass completely 

 through the island from the coast near Wellington in a N.N.E. direction. 

 They have an extreme width of about twenty-three miles, and a minimum 



