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and Waiomo Streams, whence it extends northwards towards Mercury Bay. It is a noteworthy fact that wherever it is found it contains large well-defined payable reefs. It consists of alternations of soft or moderately-hard decomposed andesites and bands of solid hornblende and augite andesite lavas, which pass imperceptibly into indurated tuffs and breccias. The decomposed andesites generally possess a characteristic yellowish-brown or grey colour, and form the ' kindly country 'of the local miners; while the solid andesites and tuffs possess a greenish or dark-blue or purple colour, and are generally known as ' hard country.' These alternating bands of soft and hard rock follow a general north-east course, and, from the Kuranui Hill to the Waiokaraka Gully, possess a north-west dip, at angles varying from 40° to 70°. From the Queen of Beauty shaft southwards the hard lavas assume an almost vertical position. The main reefs or lodes occur in the soft decomposed andesites, and follow their course and underlie. Of course it must be clearly understood that the decomposed andesites show no stratification whatever, and the apparent strike and dip which they exhibit are imparted by the narrow hard bands of undecomposed cores, whose line of outcrop follows a north-east course. The reefs in most cases run parallel to the hard bars, and where these are steep, as in Kuranui Hill and between the Waiotahi and Karaka Streams, the reefs are steep, and where they are flat, as between the Moanataiari and Waiotahi Streams, the reefs are correspondingly flat or low lying. " From the Thames foreshore the country rises to the north-east by a number of long, ascending spurs or ridges, which gradually converge and culminate at the Look-out Rocks, situated on the watershed lying between the Karaka and Ohio Streams. The ridges and spurs appear in most cases to be formed by cores of the hard country, while the creeks have excavated their courses and valleys in the softer bands. The streams which diverge from the culminating point just spoken of are the Hape, Karaka, Waiotahi, Moanataiari, Kuranui, Shellback, Tinker's, Ohio, and Otanui. " Excepting in the Karaka area, the hard bars or belts of rock are always subordinate to the soft ' kindly country ' both in width and extent. On the seaward side of the Moanataiari Fault, and in the upper basins of the Moanataiari and Waiotahi, where extensive mining operations have been conducted for a great number of years, the alternating character of the soft and hard country is very marked and distinct. " Origin of the Gold-bearing Bocks. — Judging from the character of the breccias at Tararu beach, and the more or less rudely stratified structure of the tuff in many parts of the peninsula, I am inclined to think that the volcanic eruptions which originated the rocks of the Thames Goldfield were submarine, and most probably took place in shallow seas studded with rock-girt islets. The occasional presence of masses of silicificed wood in the Hape Creek breccias clearly indicates the proximity of dry land. But while sub-aqueous eruptions were active in one case, sub-aerial volcanoes were pouring out vast deposits of fragmentary ejecta, accompanied by streams of lava 'in others. On the western slopes of the main range lying between Coromandel and Cabbage Bay the great volcanic breccias contain intercalated shales and thin seams of fine bituminous coal, composed of a terrestrial vegetation, thus proving that the eruption in that area took place on dry land. The same conditions are also indicated near Paeroa, where a thick deposit of black coaly shale, containing irregular layers of brown coal several inches thick, is intercalated among coarse volcanic breccias. " There is an entire absence of visible volcanic vents in this district; but the prominent masses of andesitic lavas and breccias in the high country at the source of the Karaka may mark the sites of ancient points of eruption. The widespread character of the volcanic ejections, extending throughout the whole length of the peninsula, would lead to the conclusion that the eruptions took place along a great fissure rent, possessing many points or foci of intense activity, a feature so strikingly illustrated during the volcanic eruption in June, 1886. " Age of the Gold-bearing Bocks. —ln the Thames district the gold-bearing rocks are found resting directly on a highly denuded surface of the Palaeozoic slaty shales ; and, since they contain no distinct fossils themselves, their age cannot be determined here, although the presence of decotyledinous leaf-impressions in the coaly shales embedded in the breccias at Paeroa and Tapu affords unmistakable evidence of their Tertiary age. But the only direct and satisfactory evidence of their age is to be found on the coast-line between Coromandel and Cabbage Bay. There, at Waitete Bay, a small isolated patch of fossiliferous strata of Cretaceo-tertiary age is found resting on a denuded surface of Palaeozoic slaty shales and grey wackes. The younger series consists of a thick stratum of coarse sandstone conglomerate resting on the slaty rocks. This is followed by marly greensands, in turn overlaid by a hard impure shelly limestone, which closes the series. A few chains back from the beach the whole series is overlaid by the gold-bearing series, consisting there of coarse breccias, with coaly shales, indurated tuffs, solid andesites, and propylites containing gold-bearing quartz-veins. The volcanic rocks are therefore younger than the shelly limestone of Lower Eocene age, and, judging from the presence of the ash-beds in the Waitemata series on the shores of the Waitemata Harbour, I am of the opinion that the eruptions began in Upper Eocene times and continued down to the Middle Eocene period. It is interesting to note that the North American andesites are considered of Lower Miocene age, as also are the andesites and propylites of Hungary and Transylvania. "High-level Terraces.—On the north side of the Kauaeranga River, in the direction of Tot ra Point, there is a high, broad river-terrace, composed of well-worn water gravels, and white quartz sands. The materials forming this terrace were transported by the river when it flowed at a higher level than at the present time. "The flat on which Irishtown is built, and the undulating and sloping ground in the area known as Block 27, are occupied by the remains of the old high-level terrace formed by the joint action of the Karaka and Hape Creeks. The original level of this old terrace is best seen at Irishtown, at the lower end of which it terminates abruptly, at a point overlooking the Queen of Beauty shaft. Its height is about 175 ft., and an examination of its face shows that it consists of numerous alternating horizontal layers of clay, sand, and gravel, with occasional bands containing