276 T'ransactions.— Geology. 
I think, therefore, that the following is a fair statement of the present 
position of the case. 
Professor Hochstetter said that there is at Coromandel a tertiary trachytic 
formation overlying vertical beds of clay-slate and lydian stone of paleozoic 
age, and he thought that the gold would be found only in the slates and not in 
the trachytic formation. Dr. Hector also says that there is a trachytic 
formation overlying slates, but that the gold is principally found in neither 
one nor the other, but in a distinct volcanic formation which is considerably 
older than the trachytes, having partaken in the movements and foldings of 
the clay-slates. 
Mr. Davis appears to have agreed with Dr. Hector. 
I agree with Professor Hochstetter that there is a tertiary trachytic 
formation overlying clay-slates, but say that the gold has been almost entirely 
obtained from the trachytic formation, and not from the slates ; and I deny 
the existence of Dr. Hector's “greenstone tufa” formation as distinct from the 
tertiary trachytic one. 
As it is now an undisputed fact that the principal mines are situated in 
a felspathic rock, and not in the slates, the question at issue is reduced to this: 
Is this felspathic rock part of the tertiary trachytic series, or is it part of a 
distinct formation more closely related in age to the clay-slates than to the 
trachyte tuffs, which have been deposited unconformably on its upturned 
edges ? 
I will in the first place, examine all the evidence that I can find in 
Dr. Hector's and Mr. Davis’ reports in favour of the distinctness between the 
“greenstone tufa” and *trachyte tufa” formations, and then I will state the 
evidence on which I rely for proving that they are one and the same. 
l. Lithological Evidence.— Mr. Davis, in his report on the Shortland 
district (Lc. passim), seems to lay stress on the great diversity of appearance 
in the rocks found there, as proving that more than one formation must exist ; 
at the same time he makes no attempt to trace out these different formations. 
Dr. Hector, also, by calling his two formations “ greenstone tufa" and 
" trachyte tufa” would seem to imply that, besides a stratigraphical break, a 
difference could also be made out in the chemical composition of his two 
formations. But to show the extreme difficulty that Dr. Hector and Mr. Davis 
must find in distinguishing between the rocks of their older and younger 
formations, I may point out that Dr. Hector, in his instructions to me in 
1867, states that Keeven’s Point, at Coromandel, is composed of non-auriferous 
trachyte tufa belonging to the younger formation (Lc. р. 2); while, in his 
report of April, 1870, he calls it a tufaceous porphyry, originally a clay-stone 
porphyry (¿e., p. 90), and again (p. 92) a grey tufaceous sandstone “ like that 
at Kapanga and Tokatea,” in both cases including it now in his older 
