Canterbury and Westland. 289 



similar brecciated structure, through which other portions, of a more 

 felsitic character in the form of dykes appear. Although this, in 

 many cases, may be only an appearance, and the effect of a different 

 state of cooling, or re -arrangement of the particles during the 

 cooling, some of those dyke-like masses may nevertheless be real 

 dykes which at various periods were ejected, and filled up fissures in 

 the previously erupted rocks of the same description. Where the 

 porphyries repose directly upon the palaeozoic sedimentary beds, or 

 upon the amygdaloids, at the junction they appear either as pitch- 

 stones or they have a more or less tufaceous character, just in the 

 same manner as a lava stream of younger origin which is stony in the 

 centre, is always scoriaceous or tufaceous at the bottom, where it reposes 

 upon other rocks. There is, however, one locality in the Gorge of the 

 Itakaia where true tufas, and even shales appear immediately below 

 the porphyries. Besides the crystals which have, doubtless, been 

 formed during the cooling of the rock, these porphyries enclose some- 

 times small pieces of slate and sandstones either angular or having 

 their edges rounded. These enclosed pieces are generally quit© 

 unaltered, but I observed one piece of sandstone which was remarkably 

 fritted. 



The quartziferous porphyries in Banks' Peninsula occur near 

 and along the opening leading from the head of Governor's Bay to 

 Lake Ellesmere, by Gebbie's Pass, and stretch as Manson's Peninsula 

 far into Lyttelton harbour. They have broken through, and cover 

 sedimentary rocks, probably belonging to the Waihao formation. At 

 the base we also find tufaceous deposits, brecciated agglomerates, and 

 shalybeds, with obscure markings of plant remains which might possibly 

 belong to them. In texture and composition these porphyries, some- 

 times containing garnets, agree with those of the more western zone, 

 whilst in other instances their compact, or sometimes felsitic matrix, 

 is full of crystals and grains of smoky quartz. When treating of 

 Banks' Peninsula, I shall return to this subject. 



Even now when the coulees, although they have become greatly 

 destroyed, possess in some localities a total thickness of 3000 feet, 

 it is evident that before the next, or Waipara formation was deposited, 

 these eruptive rocks had already been exposed for a considerable time 

 to disintegrating agencies ; consequently a long period must have 

 intervened between the eruption of the acidic rocks and the deposition 

 of the Waipara beds. Numerous specimens of fossil wood have been 

 -collected from the strata at the base of these eruptive rocks. Generally 



