22 St. J ago. 



PAET I. 



greatly in composition. The upper are basaltic, gener- 

 ally compact, but sometimes scoriaceous and amygda- 

 loidal, with associated masses of wacke : where the basalt 

 is compact, it is either fine-grained or very coarsely 

 crystallised ; in the latter case it passes into an augitic 

 rock, containing much olivine ; the olivine is either 

 colourless, or of the usual yellow and dull reddish 

 shades. On some of the hills, beds of calcareous matter, 

 both in an earthy and in a crystalline form, including 

 fragments of glossy scorias, are associated with the 

 basaltic strata. These strata differ from the streams of 

 basaltic lava forming the coast-j)lains, only in being 

 more compact, and in the crystals of augite, and in the 

 grains of olivine being of much greater size ; — characters 

 which, together with the appearance of the associated 

 calcareous beds, induce me to believe that they are of 

 submarine formation. 



Some considerable masses of wacke, which are 

 associated with these basaltic strata, and which likewise 

 occur in the basal series on the coast, especially at 

 Quail Island, are curious. They consist of a pale 

 yellowish-green argillaceous substance, of a crumbling 

 texture when dry, but unctuous when moist : in its 

 purest form, it is of a beautiful green tint, with 

 translucent edges, and occasionally with obscure traces 

 of an original cleavage. Under the blowpipe it fuses 

 very readily into a dark gray, and sometimes even black 

 bead, which is slightly magnetic. From these char- 

 acters, I naturally thought that it was one of the pale 

 species, decomposed, of the genus augite ; —a conclusion 

 supported by the unaltered rock being full of large 

 separate crystals of black augite, and of balls and 

 irregular streaks of dark gray augitic rock. As the 

 basalt ordinarily consists of augite, and of olivine often 

 tarnished and of a dull red colour, I was led to examine 



