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In a covering letter, dated the 23rd September, 1867, with which was forwarded to the Under Colonial Secretary Captain Hutton's Report on the Thames Goldfield, are the following remarks : — "The associations of gold with volcanic rocks belonging to the Tertiary period; near the point where they have been erupted through the older Palaeozoic slates, has a very important bearing on the question of the occurrence of gold in the interior of the North Island, as there is a probability that many other localities besides the Cape Colville Peninsula will prove auriferous to a similar extent. 1 see no reason, however, to expect any extensive alluvial diggings in the Karaka district, or that it will afford a field for the employment of a large mining population." From Captain Hutton's Report (his first on the Thames Goldfield), above referred to, is taken the following : — " The whole country [the district east of the Thames] is much broken, rising, except at the mouths of four of the streams, into hills of from 600 ft. to 800 ft. close to the sea, and increasing in height towards the eastern boundary of the block to more than 1,000 ft. The country is for the most part covered with dense bush (except where close to the sea), and the streams are all mountain torrents, with large boulders occupying their beds. " Geological Structure. —The geological structure of the country is very simple, being almost entirely composed of a huge mass of trachytic tufa, resting on Palaeozoic rocks, which are cut by numerous dykes mostly of diorite, but occasionally of trachyte. This tufa appears generally as a softish grey coarse-grained rock, weathering white, and sometimes much stained with peroxide of iron. Where cut by dykes it is hardened for considerable distances, and much altered in appearance. As might be expected, however, from its origin, it varies a good deal in character, often containing rounded blocks of diorite 1 ft. or 2 ft. in diameter ; indeed, in three or four places it passes into a true conglomerate, while occasionally small angular stones are seen in it, forming a breccia. These latter, however, are very local. " Near Hongikori the rounded blocks of diorite are encased with a coating of red jasper. The rock is also traversed by numerous veins of quartz, carbonate of lime, or both these minerals mixed together, in which case it is seen that the carbonate of lime is a subsequent introduction, as it is found incrusting well-formed crystals of quartz. The whole of the rock, including some of the dykes, is much impregnated with iron-pyrites, generally in the form of minute cubes, but decomposed to a grey powder near the auriferous veins. The " tufa is probably of Tertiary age, and not older than the Waitemata beds. In structure " there are no marks of bedding nor stratification to be seen, but from the extent of country that it covers, and the general vertical direction of the dykes, I think that it is not far from horizontal, dipping, probably, slightly to the west or north-west. The absence of slate boulders in the streams and on the coast seems to show that this tufa extends over much more ground than that visited by me, and I can see no reason why auriferous veins should not be found in any part of it. These veins, being thin and variable, must always render gold-mining in this district highly speculative, and if, as I believe, the stratification is nearly horizontal, deep sinking will be useless, and, in order to enable a company to make a profit, it will require more' ground than is usually allotted to a gold claim. " In one locality only, between Tararu and the Waiohanga Creeks, are Palaeozoic rocks seen in the district. They here consist of blue aranaceous slates, covered by a fine-grained felsite tufa, the whole dipping 35° south-west. " Lying on the tops of the old tufaceous hills, between Shortland and Tararu, a deposit of fine red-and-white trachytic tufa is seen, of a much later date than the old one on which it rests. This does not cover much extent of country, and is probably of Pleistocene age, and formed by the former eruptions of Aroha Mountain."* Thus, according to the above report, the mass of the country is composed of trachytic tufa, cut by numerous dykes of diorite and trachyte. The tufa varies a good deal, and contains frequent boulders of diorite; is sometimes a conglomerate, shading off into a finer-grained breccia. Quartz veins are numerous, but not large, and carbonate of lime is often associated with the quartz. The trachytic tufa is of Tertiary age, and not older than the Waitemata beds. Palaeozoic rocks are seen only on the coast-line between Tararu and Waiohanga Creeks, and a yet younger trachytic tufa of Tertiary date rests on the older, which is probably a product of Te Aroha, this mountain evidently being regarded as centre of eruption. The following extract is from the " Second Report on the Thames Goldfields," by Captain Hutton, Wellington, 1869. The extract begins with a description of the country dealt with in the report, which is as follows :— " Description of the Country. —The district included in this report is a narrow strip of land on the right or east bank of the River Thames, and on the eastern side of that part of the Hauraki Gulf known as the Firth of Thames. It is some twenty-five miles long, by two to four broad, the direction of the longer axis being about north 18° west. Shortland, the principal town, is distant from Auckland about forty-three miles by sea. At Puriri, the southern end of the district, the alluvial plain on this bank of the Thames is about three miles broad, and it gradually narrows until it comes to an apex at the Kuranui Creek, north of Grahamstown. The remainder of the country is hilly, the hills having generally very steep slopes, and rising to about 2,300 ft. near the head of the Karaka. The sides of the hills are generally covered with slipped ground and vegetable soil; very few precipitous places occur, and with the exception of the beds of the streams or creeks, and occasional landslips, are the only natural sections to be found. The most important of the creeks beginning from the south are the Puriri, the Kauaeranga, the Tararu, the Puru, the Waionau, the Pohue, the Tapu, and the Mata. The first two run for the last few miles of their course through alluvial flats; but all the others are mountain torrents almost to their mouths, their beds consisting

* " Geological Reports on Thames Goldfields," 1867 : first report, by Captain Hutton.