HuTTON. — On the Thames Gold Fields. 279 



grey tufaceous sandstone, full of mundic, as at Keeven's Point and Kapanga, 

 thus proving this vock to extend in a narrow belt from the sea level to 

 1,600 feet altitude." I do not see how finding a rock at three ditferent places 

 in a line, and at very different altitudes, can prove that it runs in a narrow 

 belt. It seems to me that the absence of the rock on either side of the belt 

 should be first j)roved ; but I have myself traced this rock for several miles in 

 a direction nearly at right angles to the line indicated by Dr. Hector, and it 

 must be remembered that if the gold should be found to run only in a narrow 

 belt it would by no means imply that the- bed-rock did the same ; for the 

 distribution of a rock is one thing, and the distribution of gold in that rock is 

 quite another thing. He also says (^.c, p. 92) that " the auriferous reefs are 

 generally in the decomposed rock, and, as at Shortland, have a general direction 

 parallel with the boundaries of the formation, or N. 40° E." But in his 

 map of the Coromandel district he shows his " greenstone tufa " formation 

 running in a nearly north and south direction, and without a single boundary 

 approaching to a N. 40° E. direction. As Dr, Hector has not attempted 

 to map his formations at Shortland, I cannot tell where he supposes the 

 boundaries to lie in that district. 



At Tapu, he says (I.e., p. 98) that "■ the reefs are in bands of greenstone 

 porphyry, which intersect the slates with a prevalent north-east strike." But 

 most of the claims (except those in the slates) are situated in a brecciated rock, 

 which is certainly not intrusive, and could not intersect slates ; neither can it 

 be interbedded with them, for the slates here are nearly vertical, and strike 

 east and west. As Dr. Hector has not mapped any of these bands I do not 

 like to speak positively on the subject, but their occurrence in the way that he 

 describes them appears to me to involve a physical impossibility, and, although 

 I made a careful survey of- the district, I saw nothing that would lead me to 

 adopt his opinion. 



Mr. Davis asserts (I.e., p. 99) that south of Hastings the older volcanic 

 formation strikes north and south, while the more recent tufas are nearly 

 horizontal ; but, from a personal inspection of the locality, I am convinced 

 that Mr. Davis mistook jointing for bedding, there being no planes of strati- 

 fication visible, while his more recent tufa is but the older one decomposed. 

 I made the same mistake myself in my first report on the Thames. Mr. Davis 

 also appears to think that, as a tufaceous breccia is found at the Thames 

 enclosing fragments of tuff or breccia, it necessaiily proves two distinct 

 formations. But this is by no means the case, for it is a common phenomenon 

 in all submarine volcanic districts. When an eruption is over, the vent fills 

 lip and consolidates, and a subsequent eruption breaks this up into fragments 

 and scatters them around. An example of this may be seen in the Auckland 

 Domain, in a cutting through basaltic tuff of newer pliocene or pleistocene age. 



