Canterbury and Westland. 285 



quartziferous porphyries. In the Malvern Hills they crop up along 

 the sides as well as towards the centre of the acidic zone where the 

 rocks belonging to the latter have been much denuded. In the gorge 

 of the Rakaia, where fine sections are exposed, they occur in the 

 centre, being flanked on both sides by the porphyries. The relations 

 of these rocks to each other are still more clearly exhibited in the 

 Ashburton-IIinds zone, where the melaphyres occupy the outer 

 margin, the quartziferous porphyries forming the centre and covering 

 the former. On Section-plate No. 3 I have copied from my field-books 

 some of the most interesting sections, illustrating the relations in 

 which these eruptive rocks stand to each other. 



Qtjaetzifeeotts Poephyey and Pitchstone Seeies. 

 The basic rocks just described are, as previously stated, covered in 

 many localities by a series of quartziferous porphyries and pitch stones 

 which in Mount Somers reach an altitude of 5223 feet. An examina- 

 tion of the junction of these two series of eruptive rocks in several 

 localities, showed that the older rocks had undergone considerable 

 denudation, or, at least, that their surface had been altered considerably 

 by aqueous agency before the next beds were deposited upon them. 

 Thus, for instance, among the Clent Hills, in Junction Creek which 

 joins the Stour, the uppermost beds of the melaphyres consist 

 of a very decomposed amygdaloid, gradually changing into a green 

 tufa of the quartziferous porphyries ; upon them repose pitchstones, 

 from a greenish-white colour gradually assuming a black tint, and 

 becoming very vitreous. The porphyries which lie upon them, or 

 more correctly speaking, of which they form the lowest portion, have a 

 hyaline base, and follow each other in many streams, but generally with 

 a layer of pitchstone betweem them. The principal localities where 

 these porphyries are found are in the Malvern Hills, Hinds, Ashburton 

 and Banks' Peninsula districts. Although of a great variety of 

 texture and colour they resemble each other in their principal charac- 

 teristics, a porphyritic structure with grains of quartz and small 

 crystals of garnets (almandine) being predominant. I have already 

 alluded to the fact that these porphyries lie directly in some localities 

 upon the melaphyres, but in other places they repose upon the 

 palaeozoic sedimentary rocks, the streams of which they are composed 

 following the outlines of the former sea-bottom, and beino- at the 

 same time underlaid by a succession of truly sedimentary deposits of 



