420 Transactions. — Geology. 



lin. to 2 in. in diameter and slightly waterworn. Above this 

 the matenai is finer and similar to that met with on the 

 southern side of the harbour, at Judge's Bay and Point Erin. 

 Through the band are scattered numerous angular or sub- 

 angular fragments ranging up to 8 in. or more in diameter. 

 Some of these are close and compact ; others, again, are 

 vesicular and amygdaloidal, the infiltrating mineral being 

 principally calcite. 



The rocks comprising the fragments are considerably 

 altered and weathered, the feldspar crystals being many of 

 them kaolinised. Large crystals of augite are plainly visible 

 in most of the included fragments. 



A section from one of the fragments examined under the 

 microscope showed a microcrystalline ground-mass consisting 

 of a tricliuic feldspar, minute augite crystals, and numerous 

 specks of magnetite, with larger porphyritic crystals of 

 feldspar and augite, as well as those of an altered mineral. 

 Many of the feldspars were kaolinised, and most of them con- 

 tained inclusions of magnetite and augite. They were tri- 

 clinic, and comprised the varieties andesine and oligoclase. 

 Small augite crystals were numerous, but only a few were 

 idiomorphic. The crystalline form and mode of occurrence of 

 the altered mineral suggested the possibility of its being 

 altered olivine. On the whole, however, the evidence was not 

 sufficient to pronounce definitely on the constituent. The 

 rock is obviously an augite-andesite containing perhaps a 

 little olivine. (See rock section D, Plate XXV. ; specific 

 gravity, 2-8.) 



The first outcrop of conglomerate and grit met with is at 

 the north end of Cheltenham Beach. The band dips east at 

 an angle of 35°, and, running nearly horizontally for about 

 200 yards, suddenly disappears, as shown in fig. 3. From 

 this onwards the strata are much disturbed and faulted, 

 in places being thrown on end. Beyond a well-marked dome 

 a little further north the grit again appears in a band 

 some 8 ft. or 10 ft. thick, but the thickness cannot be accu- 

 rately determined as the band does not show well in the 

 cliff. Here it dips west at an angle of about 15°, and, running 

 out to sea, forms a long reef. From this point northwards for 

 a few hundred yards the cliffs give place to a low sandy flat 

 over which the sea flowed not many years ago, but which 

 has now become dry, the land being raised partly by the 

 wash from the hills and partly by the sand carried in by wind 

 and sea. When the beds (Waitetnata) next appear they are 

 dipping west at an angle of 20°. Half a mile or less further 

 north from the outcrop of grit mentioned last another 

 exposure of the same material occurs. Here the band strikes 

 north and presumably dips west ; but, as it only shows as a 



