128 Transactions. 



Several cones with a erater-like character show us the different centres of 

 eruption ; whilst around them, and extending from one to the other, marine 

 sands have formed barriers, enclosing tracts of low land favourable to the 

 formation of peat swamps. 



Pitt's Island is formed of the same volcanic rocks, but it is more hilly, 

 and does not present the same strange aspect as the main island. 



The rocks submitted to me, with the necessary explanations, by Mr. H. 

 H. Travers, afford a clear insight into the structure and formation of these 

 islands, and to them I shall refer when speaking of the different characters 

 of the rocks. 



The oldest rocks visible occur near Kaingaroa, and stretch in a west and 

 east direction towards the north-eastern corner of Chatham Island. They 

 dip towards east at an angle of about 30°, and consist of micaceous clay- 

 slates, silky, and of a pale green colour. They are traversed by veins of 

 quartz which has the appearance of being auriferous. Similar rocks occur 

 in our Southern Alps of Ncav Zealand, on the eastern slopes of the Moor- 

 house range, and on the south-western slopes of Mount Cook. Smaller 

 outcrops of this rock occur at the north-western corner of the large salt- 

 water lagoons, and at Wangaroa or Port Hutt. Some beds of limestone 

 fringe the south-western shores of that lagoon, to which, judging by their 

 mineral character, we may assign a very high age. This limestone is of a 

 white colour, and very crystalline ; its structure is somewhat vesicular, but 

 as the specimens submitted to me are rather small, it is difficult to assign to 

 this limestone its true age, although, in its general character, it has all the 

 appearances of a palaeozoic limestone. 



As before stated, the main eminences of the principal island are formed 

 by basaltic rocks, which contain often large concretions of hornblende, 

 augite, and chrysolite. At their base, basaltic rocks, which often form 

 perfect cones, and tufa beds, are met with, which in lithologicpj character 

 are identical with those of the same age in New Zealand. 



The collection of rocks from Pitt's Island is far more complete, enabling 

 me to examine the fossils which they contained, and thus assign to them 

 their true age. 



The lowermost rocks resemble those from the main island, already de- 

 scribed, of a basaltic and doleritic character. On them, and on the western 

 side, repose palagonite tufas, identical with those associated with our tertiary 

 doleritic rocks in the Malvern Hills, Mount Somers, &c. On them, again, 

 we meet with calcareous fossiliferous tufas, changing by degrees from an 

 agglomerate containing large pieces of volcanic breccia cemented together 

 by a sandy matrix, with a slight admixture of carbonate of lime and only 

 traces of fossils, to a tufaceous whitish limestone, enclosing great quantities 



