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large rounded boulders of decomposing andesite. On the south side of the Karaka the original level of the old terrace can only be traced in a few places, the small streams which descend from Una Hill having excavated it into broad undulating spurs, which are now largely built upon. A portion of the old Hape Creek terrace is well preserved at Mount Pleasant, and in the road-cuttings in that neighbourhood the bedded character of the materials is very clearly been. Both in the Karaka and Hape Creek areas the terrace-clays often contain numerous large subangular masses of solid andesite. " A small patch of the Waiotahi old high-level terrace is still preserved opposite the Cambria battery, at the point where the stream issues from its valley. " The Moanataiari Fault forms the north-east boundary of the terrace-materials along the foot of Una Hill, but no evidence can be obtained to show whether the Great Fault is older or younger than this Pleistocene gravel and boulder-formation, but at present I favour the opinion that it is of somewhat older date. " The Alluvial Flat, and Floor of the Harbour. —The alluvial deposits on the foreshore have been exposed by different shafts and borings to a depth of 90ft. from the surface; and by levels driven from the New Prince Imperial and Piako shafts to a depth of 300 ft., or 400 ft. A shaft sunk in Shortland, in 1868, passed through 2 ft. of surface soil, 10 ft. of shelly sand, 68 ft. of blue and yellow clay, mixed with boulders of andesite, and 10 ft. of pumice-sand. The actual depth of pumice-sand was never determined. The information disclosed by the seaward levels shows that the floor of the old harbour is occupied by a great boulder formation, composed of materials similar to those forming the high-level terrace behind Shortland. For a number of years no mining operations have been carried on from the shafts on the foreshore in the direction of the harbour, so that the data relating to the existence of the supposed beach slide or fault is of a very meagre kind. In consequence of this, it is impossible to definitely decide whether the boulder and clay formation met with on the floor of the harbour is really a faulted portion of the Shortland terraces, or merely the accumulated waste of the back country. " Geological History of the Hauraki Peninsula. —During the whole of the Secondary epoch this area was occupied by a deep still sea, devoid of islands or islets. With no dry land to waste, no sediments were formed during this long period of time. New Zealand throughout the Secondary epoch —like Great Britain —seems to have been singularly free from volcanic activity and all great earth-movements. But at the close of the Cretaceous period the land in this area began to gradually emerge from the sea, and an island of large size appeared to the north-east of the present site of Coromandel. The ever active agencies of denudation at once began to wear away the dry land, and the spoil was carried to the sea by numerous streams and rivers. After a period of rest, the land began to sink, and the peaty deposits which had accumulated on the low-lying marshy Shores of the island were soon submerged, and in their turn became covered with coarse gravels, sands, and clays carried seaward by the streams which descended to the coast-line. The land still continued to sink, and, as the sea encroached, true marine deposits were formed above the fluviatile materials, and, as shelly limestones, closed the sequence of the coal-measures, and marked the complete submergence of the dry land. But with this disappearance the quietude which New Zealand had so long enjoyed was rudely broken. Submarine volcanic eruptions of the most violent and widespread nature now took place. Great fissure rents opened in the floor of the ocean, and poured out vast quantities of ashes and floods of fiery lavas which soon became piled up, until many of the volcanoes reared their heads above the water. This stupendous outburst took place in Upper Eocene times, and is marked by a characteristic fossiliferous ash-bed in the Waitemata series, whose sediments were accumulating at this time in the quieter seas in the Western Hauraki region. This bed, well known as the ' Parnell grit,' consists of sea-borne ashes and mud, and occasionally angular fragments of solid hornblende and augite-andesite lavas, often several inches in diameter. "After the pent-up forces had spent themselves in the first great paroxysm there was a period of rest from volcanic activity, during which vegetation established itself on the mud and ashes washed into the low grounds by the streams draining the slopes of the newly-formed volcanoes. But the land was in a continual state of tremor, and the oscillations too frequent to permit the continued growth and accumulation of sufficient vegetation to form workable seams of coal. The cessation of volcanic activity was of short duration. The plutonic forces burst out with renewed energy. The forests were devastated and utterly destroyed, and covered by hundreds of feet of ashes and solid lavas, first of a semi-basic and then a trachytic character. The embedded trees in many cases were converted into wood-opal by the petrifying action of the thermal springs, which appeared when the volcanic forces had become once more dormant. The land along the line of eruption now began to emerge from the sea, but the process was accompanied by violent earthquakes and convulsions of the land. The enormous strain following the consolidation and cooling of the vast accumulation of volcanic ejections, no doubt aided by the settling of the crust, due to the great excavations made below, originated numerous deep-seated parallel fissures running in a north or north-east direction. The expiring volcanic forces still manifested themselves in solfatara action of an intense kind along these fissures, which probably coincided approximately to the general trend of the original line of fissure-rent. " The thermal waters, steam, sulphuretted hydrogen, and other acid vapours, soon began an energetic attack upon the amphiboles, pyroxenes, feldspars, and other complex silicates forming the matrix of the semi-basic lavas. The silica became separated from its bases, and soluble alkaline silicates were formed as well as soluble salts of the metallic bases. After the leaching had thus proceeded for a long time, and the solfatara action had become feeble, the alkalies found new combinations, and the liberated silica, in the form of quartz, became segregated in the cracks and fissures, and distributed in fine grains throughout the mass of the leached lavas. While the changes which caused the liberation of the quartz were in operation, the fissures, now charged with alkalies as alkaline sulphide, became great voltaic cells, and the theatre of electro-chemical action. The