24

E.—lo

Coal has not yet been found between the vicinity of the coal mine and the edge of the first step of the plateau, where the east branch of Mine Creek commences to fall rapidly into the valley ; but this is only due to the absence of natural sections, and as this part of the coal is included in the Company's leasehold, and will be worked as part of the present mine, I did not think it advisable to incur the great expense that would be necessary to prove the seam in this part of the field. Indications of two faults are visible in following the boundary of the formation in a south-easterly direction from Mine Creek. They both bring tho granite to the surface, as shown approximately on the plan, and will interfere with the continuity of the coal workings, but will not materially diminish the area of available coal. The altitude at which the next outcrop has been found (marked Aon plan) is at 750 feet above sea-level. The seam is exposed in the bed of the east branch of Mine Creek, and can be traced in the bank for some distance, with a dip of 20° to N.W., and a thickness of 3' 6" of clean bright coal, with a roof of hard sandy shale, and a floor of dark grey sandstone. Following up the creek to the S.E. the floor of the stream is formed by the strata beneath the coal for 15 chains, which are hero coarse grits and sandstones, the ledges forming falls. Several small faults are distinctly seen running S. 30° E., aud dropping the strata 4 to 10 feet to the west. These are only mentioned as they serve to indicate the manner in which the coal measures are bent over the edge of the plateau, on which they are comparatively level, and acquire the high angle of dip which they have in Mine Creek. At the point marked B the bed of the stream has again risen on to the cover of the coal, and the seam is exposed in the face of a waterfall, showing 3 feet of coal, with a dip of 15° W. This outcrop is 980 feet above the sea, and is situated about the extreme S.E. corner of the leasehold that has been granted. At this elevation the open rolling country of the plateau commences, the bush and scrub being chiefly confined to the gullies. Terracelike steps stretch to the westward, until they are cut oft' by the scarp of Mount Frederick, leading down to the sea, as shown in sections AB and CD. Evidence of the extension of tho coal seams throughout this part of tho field is found in the occurrence of the two outcrops discovered by Mr. Dobson in Gravity Creek, at 1,350 and 1,600 feet altitude. I examined the lower of these, marked Con the plan, and found the coal is very imperfectly exposed in the bottom of a deep ravine, but it appears to be at least 10 feet thick. A short distance above this coal, a spur of the granite from Mount Frederick is at the surface, forming a wooded hill; and at the upper or eastern boundary of this, the true high level of the plateau commences, with an average altitude of 2,000 feet, the surface of which, though undulating, is never abrupt, except in tho ravines, and is formed of the sandstones, grits, and interbedded shales of the coal measures, which dip at moderate angles, and are much less disturbed than in tho part of the field abovo described. The ravines, which arc from 50 to 100 feet deep, frequently expose good sections of tho strata; and near the source of the east branch of Mine Creek the coal can be traced continuously for about 20 chains, with tolerable regularity. At D, on the plan, this seam is seen to great advantage on both sides of a precipitous gorge, where it forms vertical cliffs of hard black coal, that appear to resist tho action of the weather. As the floor of the creek is also coal, the full thickness of the scam was not ascertained ; but about 22 feet is exposed in the section. The coal is laminated, with a bright fracture, and closely resembles the coal that was mined at Coalbrookdalo, which differs from the Ngakawau only in its greater coherence and lustre, and in the larger proportion of gaseous matter which it contains. The seam is easily traced in the bank of the river to the N.E., as shown on the plan; but iv that direction it thins rapidly, and is cut by a succession of small faults. In the opposite direction the outcrop is obscured by scrub for some distance, but it is again exposed in a landslip by a slight excavation. It is then seen crossing the bed of the next highest branch of the creek at D, which is the last exposure in that direction. In a southerly direction, the seam underlies the area marked " Plateau Coal" for the distance of a mile, as what must be the same coal again appears in the ravine of the south branch of the Ngakawau River at the point marked E. This is the largest block of coal which has yet in this district been defined with tolerable accuracy, aud by a moderate estimate is computed to contain 7,000,000 tons. Coal has been seen in many of the ravines between this point and Coalbrookdale, which is distant seven miles to the south, so that it is very probable that tho coal is continuous for that distance; but until there is a map of the country on which these can be accurately laid down, any reference to them might only tend to mislead in estimating the extent of coal which they indicate. The chief difficulty in working this coal will arise from its inaccessible position, and the absence at that altitude on the mountain of any timber suitable for mining purposes. AVhile the coal is obtained with such facility and economy of capital at the Ngakawau Mine. High level coal on the plateau is therefore not likely to be worked—not at least till a large trade is created; and as during the interval the district will become better understood, it is premature at present to discuss the manner in which access can be obtained to that part of the field. lam however confirmed in the opinion formerly expressed, that the natural outlet will be to the Ngakawau or its immediate vicinity, so that any works undertaken for the conveyance of the coal from there will serve ultimately for the whole field. It is true that a very direct but steep line might be found by following the west side of Granity Creek, but this would still reach the coast within a mile of the Ngakawau Elver. No coal has yet been discovered in the course of Granity Creek, except that already mentioned as occurring near its source ; but there is reason to think a seam may be found at a low altitude, and under circumstances almost as favourable for being worked as at the Ngakawau Mine. For a mile back from the sea the stream is in a deep gorge, and flows over the same dark marly sandstone as those overlying the coal further north. A vertical fall of 200 feet then occurs, the upper part of which is over coal grits and sandstones, like those underlying the coal on the plateau. The cliff marked by this fall forms the edge of the terraced area between the plateau and Mine Creek ; and tho only difference between the section here exposed and that at tho coal mine is, that the grits below the coal appear to have thinned out against the granite of Crane's Cliff. If this view is correct, the horizon of the coal should cross the gorge of Granity Creek below tho fall, as indicated on the plan.