282 Geology of 



"We have no data from which we can judge when those rocks 

 appeared, but there is sufficient evidence to show that they broke 

 through the palaeozoic beds upon which they rest unconformably, after 

 the latter had generally assumed their present positions, and their 

 surface had already been denuded and partly decomposed ; in fact, a 

 very long period of time must have elapsed before the first eruption 

 took place. 



Extent. 



In this group I include the melaphyres with their tufas and 

 amygdaloids, the felsitic and quartziferous porphyries with their 

 pitchstones and tufas of the East, and the melaphyres of the West 

 Coasts. The first zone begins in this province on the southern 

 declivities of Oxford Hill, where a small outlier of melaphyres and 

 amvgdaloids occurs. It then becomes largely developed in the 

 southern portion of the Malvern Hills, and on both banks of the 

 Eakaia, near the Upper Ferry. In this district, the melaphyres rise 

 to an altitude of 2900 feet, and the quartziferous porphyries to 3019 

 feet (in High Peak). 



Another small outlier of the latter is situated five miles from the 

 beginning of the Canterbury plains, on the right bank of the northern 

 Ashburton. On both banks of the southern Ashburton and Hinds 

 rivers, both divisions of these eruptive rocks cover a large area, forming 

 the summits of mountains of considerable dimensions, the basic rocks 

 rising in the Clent Hills to 4100 feet, and the acidic rocks in Mount 

 Somers to 5223 feet. The latter also crop up in one locality on the 

 southern banks of the Orari. Another zone, possessing very interesting 

 features, is found on Banks' Peninsula, consisting of quartziferous 

 porphyry, pitchstones, and some tufaceous beds derived from them ; 

 whilst we meet, on the northern declivities of Mount Harper, with a 

 small zone of melaphyre ; on the right or southern banks oE the 

 Eangitata, between Forest and Coal Creeks, a large portion of the 

 McLeod range consists of felsitic porphyry, amygdaloids and mela- 

 phyres, stretching across into the Upper Orari. In the more southern 

 portions of the province, no eruptive rocks were observed by me 

 in situ, but I found repeatedly boulders of similar porphyries in the 

 lower Waihao, without however being able to discover the locality 

 whence they became detached. I believe that the porphyries in the 

 River Mandamus, north of the Hurunui, and in the Leslie Hills, north 



