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Lower Tertiary Beds (probably of Lower Miocene age).—These extend throughout the district from its southern limit to Waipiro Bay and the Waiapu Valley, abreast of the eastern spurs of Hikurangi Mountain. The lowest beds in the northern part are a coarse conglomerate or breccia, consisting mainly of crystalline rocks, principally composed of hornblende, which often show a schistose structure. These rocks, between the Mata River and Tawhti Mountain, on the north side of Tokomaru Bay, are of great thickness. In this part they contain fragments of white limestone and spherical concretions derived from the Cretaceous rocks, proving the unconformable relationship of the two formations. The dark hornblendic boulders reach south into the valley of the Waipaoa above the junction of the Mangatu, and in the deep gorge above this junction the river-gravels show numerous hornblendic boulders up to fully 2 ft. in diameter. The Waipaoa Gorge has been excavated in sandy clays and sandstones belonging to this formation. In the gorge the source of the hornblendic boulders is not seen, but to the west, where this formation shows its lower beds resting on the upper division of the Cretaceous rocks, a thickness of the hornblendic breccia conglomerate is present, and by means of the tributary creeks debris from the same finds its way both into the Wapaoa and the Mangatu. A few boulders of the same rock are met with in the watershed of the Waikohu, but this seems to be the limit south of the hornblendic boulders. The next succeeding rock is a great thickness of sandy and marly clays, with beds of grey or yellowish-brown sandstone, often fossiliferous ; and near the base of this part a coralline foraminiferous limestone, which latter is seen on the hill forming the spur between the junction of Oilspring Creek and the Waipaoa, on upper side of the creek, or between that and the Minerva borehole ; and the same rock appears in the gravels of the Waikohu at and near the Pohutu Accommo-dation-house. Elsewhere this limestone has not been observed. The bulk of this formation in the southern part of the district is a marly clay, with segregations, in veins, of a more calcareous character. Near Dobbie's there is a proportion, sometimes considerable, of greensand grains in the more sandy rocks. These rocks strike north-east and dip to the south-east in the Upper Waipaoa. In the Waikohu the strike is more to the west, and the dip both to the north and the south, an anticline being thus formed, which runs along the low grounds of the Waikohu Valley. Between Karaka and Dobbie's the section across these beds was not examined, but it is fair to assume from what was noted elsewhere that, the formation being of very considerable thickness and still dipping to the south, it does so throughout, and that there are no anticlines and synclines in the intervening space. It is true that the nature of the rocks at Dobbie's indicates the lower part of the beds, a considerable proportion of greensand grains being present in the more sandy beds. Near Dobbie's, as elsewhere, these rocks are much subject to slips at and near the surface, and this prevented the making-out of the true strike and dip of the beds. On the coast-line between Poverty Bay and Tolaga Bay these rocks are thrown into a number of sharp anticlines and synclines, and are met with often standing at high angles, and as often at moderate or low angles; and this disturbed state of the beds probably continues across the intervening hilly country to the watershed of the Waingaromia. From the source of the Waitangi to Tokomaru Bay, except along the coast-line, these beds have not been examined. Pliocene Rocks. —These consist of sandy clays and pumice sands, capped by limestones. They occupy a considerable area west of Poverty Bay and the lower Waipaoa River, and also on the east side of the valley north and south of Gisborne. The same beds are present at Gable-end Foreland, and farther north in the vicinity of Tolago Bay. Generally they are found resting at low angles, and form remarkable terraced country on the east side of the Waipaoa, above Karaka, and on the west side of the plain in the same neighbourhood a small area shows the presence of pure white pumice sands. The pumiceous beds form poor soils, but the farmers of the district do not apparently appreciate the cause, the pumice sands being classed with papa country, which generally forms good soil. The limestone forming the upper part of the formation is quarried at two places—near Ormond, and in the valley of Waikakariki Stream, west of Patutahi. At Ormond the limestone resembles the Scinde Island limestone, and is not more compacted. West of Patutahi it is denser, and forms altogether a better road-metal, for which purpose it is used in the neighbourhood, and is also, for the same purpose, carted to Gisborne. Recent. —These rocks are found along the beach in places as littoral beach deposit and blown sands. Over the lower Waipaoa Plain and the upper plain above Karaka the alluvial deposits consist chiefly of the harder parts of the Cretaceous and Lower Tertiary formations ; Palaaozoic sandstones do not enter into the composition of these beds. The only very hard or crystalline rocks that enter into their composition are the dark hornblendic rocks that have been described as occurring at the base of the Older Tertiary formation. These, from their unyielding character, make a considerable display as far down the valley as Karaka. The Cretaceous and Older Tertiary Rocks as a Source op Petroleum. At many places in these rocks indications of mineral oil, whether as gas or oil-springs, make appearance at the surface, and therefore it would appear that the search for profitable oil-wells should be attended with success. The history of past undertakings with this object in view is not by any means satisfactory ; but what the cause of failure, whether from an injudicious selection of the places where boring was carried on, or from an actual scarcity of oil in the strata, is as yet uncertain. At all the three principal places where bores were put down the strata was penetrated to a considerable depth, and the shallowness of the holes cannot be said to be the cause of want of success. In the case of the Southern Cross boreholes, in the Waiapu Valley, strong indications of oil appeared near by. On the South Pacific Company's holding, in the Waipaoa, the most powerful natural springs of oil were at no great distance —about four miles—from where the deepest bore was put down; and several bores and shafts were put down at the springs, but none of these were of considerable depth, and the deepest did not pass through the disturbed ground and into solid rock.