HuTTON. — On the TJuxmes Gold Fields. 275 



visited the Thames gold fields, and, in April, 1870, he made a report 

 (Geological Reports, 1871-72, p. 88) in which he somewhat altered his former 

 views, although still not agreeing with me. After giving Professor Hoch- 

 stetter's opinion, he says (p. 89) that " the gold is not, however, as he 

 (Professor Hochstetter) supposed, derived only from quartz-veins in clay-slates, 

 for, as Captain Hutton very justly points out in his report on this district, the 

 area of these exposed at the surface is very limited. On the other hand 

 Captain Hutton, in the same repoi-t, does not distinguish between the 

 cpm2:)aratively modern breccias and agglomerates, which he describes as 

 containing blocks of variously-coloured scorias and lavas, and the more ancient 

 formation of green tufaceous sandstone and porphyry, in which most of the 

 auriferous lodes occur." And in the section that accompanies this report he 

 makes his " greenstone tufa " and "greenstone porphyiy," as he here calls 

 them, conformable to the clay-slates and dipping with them at a high angle. 

 But speaking of the Tapu district, he says (I.e., p. 98) that here the reefs 

 occur in " the decomposed slates and bands of greenstone porphyry which 

 intersect them with a prevalent north-east strike." It therefore ajDpears that 

 more extended observations led Dr. Hector to abandon the idea that the 

 "grey pyritiferous rock," in which the auriferous veins occur at Coromandel, 

 is a dyke of trachyte, and to suppose now that it is part of a " green tufaceous 

 sandstone and porphyry," belonging to a formation distinct on the one hand 

 from the older slates, and on the other from the newer trachyte tufa ; but he 

 still thinks that at Tapu the reefs are in dykes of " greenstone porphyry " 

 intersecting the slates. 



The late Mr. E. H. Davis also visited these gold fields in May, 1870, and 

 reported (Geological Reports, 1870-71, p. 56), as far as I can understand him, 

 in favour of two volcanic formations, one of '^'diorite sandstone," the other of 

 " tufa "; and these are, I presume, meant to be identical with Dr. Hector's 

 " greenstone tufa " and " trachyte tufa " formations respectively. But he 

 describes Tinker's Gully as "a mass of diorite sandstone with dykes of tufa 

 passing through it" (!) (p. 60), from which I infer that he supposed these two 

 " formations " (?) to be iuterstratified and elevated on edge ; and in other 

 places he seems to think that the "tufa" is only the "diorite sandstone" 

 decomposed. But however this may be, he was, at any rate, of opinion 

 (according to Dr. Hector, I.e., p. 98) that " the Tapu district furnishes very 

 conclusive evidence of two distinct and two widely separated volcanic 

 formations." 



In April, 1872, I again visited Coromandel, in order to examine some coal 

 seams which had been lately discovered, and which I shall presently describe, 

 and I then saw sufficient evidence to confirm me in the views that I had 

 previously expressed. _^ 



